COSEWIC Assessment and Status Report on the Mapleleaf Quadrula quadrula, Great Lakes - Upper St. Lawrence population and Saskatchewan - Nelson Rivers population in Canada - 2016

Mapleleaf

Mapleleaf
Photo: © Philip McColl, Graphics Arts Section, National Water Research Institute

Great Lakes - Upper St. Lawrence population
Special concern
2016

Saskatchewan - Nelson Rivers population
Threatened
2016


Document information

COSEWIC Assessment and status report on the Mapleleaf Quadrula quadrula in Canada - 2016

COSEWIC Assessment and Status Report on the Mapleleaf

COSEWIC
Committee on the Status
of Endangered Wildlife
in Canada

COSEWIC logo

COSEPAC
Comité sur la situation
des espèces en péril
au Canada

Committee on the Status of Endangered Wildlife in Canada (COSEWIC) status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:

COSEWIC. 2016. COSEWIC assessment and status report on the Mapleleaf Quadrula quadrula,Great Lakes - Upper St. Lawrence population and Saskatchewan - Nelson Rivers population, in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 86 pp. (Species at Risk Public Registry website).

Previous report(s):

COSEWIC 2006. COSEWIC assessment and status report on the Mapleleaf Mussel Quadrula quadrula (Saskatchewan-Nelson population and Great Lakes-Western St. Lawrence population) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 58 pp.

Production note:

COSEWIC would like to acknowledge David Zanatta, Jordan Hoffman and Joseph Carney for writing the status report on the Mapleleaf. This report was prepared under contract with Environment and Climate Change Canada and was overseen by Dwayne Lepitzki, Co-chair of the COSEWIC Molluscs Specialist Subcommittee.

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment Canada
Ottawa, ON
K1A 0H3

Tel.: 819-938-4125
Fax: 819-938-3984
E-mail: COSEWIC E-mail
Website: COSEWIC

Également disponible en français sous le titre Évaluation et Rapport de situation du COSEPAC sur la Mulette feuille d’érable (Quadrula quadrula), population des Grands Lacs et du haut Saint-Laurent et population de la rivière Saskatchewan et du fleuve Nelson, au Canada.

Cover illustration/photo:

Mapleleaf - Provided by Philip McColl, Graphics Arts Section, National Water Research Institute.


COSEWIC Assessment summary

Assessment summary - November 2016

Common name
Mapleleaf - Great Lakes - Upper St. Lawrence population
Scientific name
Quadrula quadrula
Status
Special Concern
Reason for designation
This heavy-shelled mussel, shaped like a maple leaf, has a limited distribution in southern Ontario. There is evidence of an ongoing, but slight, decline in the range over the last three generations. Low-impact threats, including those from Zebra and Quagga mussels, habitat alteration, and pollution continue. Despite these threats, this population is estimated to be large (millions of animals) and apparently stable at a number of locations in Lake St. Clair, Lake Erie, and western Lake Ontario watersheds. The change in status since the original report is a result of increased sampling effort across the region, newly discovered locations, and evidence for recent gene flow across Lake Erie, which suggests the potential for rescue.
Occurrence
Ontario
Status history
Designated Threatened in April 2006. Status re-examined and designated Special Concern in November 2016.

Assessment summary - November 2016

Common name
Mapleleaf - Saskatchewan - Nelson Rivers population
Scientific name
Quadrula quadrula
Status
Threatened
Reason for designation
This heavy-shelled mussel has a small range and few locations, and occurs in habitat projected to continue to decline in quality. Present and ongoing threats include pollution from agricultural effluent, urban wastewater, and industrial sources. The arrival and establishment of invasive Zebra Mussel in 2013 represents a new threat of likely high severity. This change in status is a result of new surveys revealing previously unknown locations.
Occurrence
Manitoba
Status history
Designated Endangered in April 2006. Status re-examined and designated Threatened in November 2016.

COSEWIC
Executive summary

Mapleleaf
Quadrula quadrula

Wildlife species description and significance

Mapleleaf, Quadrula quadrula, is a freshwater mussel. The shell is thick, squarish in outline and ranges in colour from yellowish green through light brown to dark brown. Typically, the species can be recognized by two rows of raised bumps or knots extending in a v-shape from the umbo (the beak that protrudes above the hinge of each valve) to the ventral edge of the shell. There are occasional deviations from this nodule pattern. Canadian specimens reach 130 mm in length, 100 mm in height and 50 mm in width. The interior of the shell is white with heavy hinge teeth.

Distribution

In the United States, this species occurs throughout the Ohio-Mississippi drainages ranging from Texas to Alabama in the south to Minnesota and Pennsylvania in the north. Its distribution extends into the Great Lakes drainage in Minnesota and Wisconsin to New York and into the Red River drainage in Minnesota and North Dakota. In Canada, this species is limited in southern Ontario to the coastal areas and medium to large rivers of the Lake Huron, Lake St. Clair, Lake Erie, and Lake Ontario watersheds. In Manitoba, the species is found in the Red River and some tributaries, the Assiniboine River, and Lake Winnipeg and some tributaries.

Habitat

Quadrula quadrula occurs in a variety of habitats ranging from medium to large rivers with slow to moderate current, to lakes and reservoirs in mud, sand, or gravel bottoms. In Ontario and Manitoba, Q. quadrula is most typically recovered from medium to large rivers in firmly packed coarse gravel and sand to firmly packed clay/mud bottom.

Biology

Quadrula quadrula is dioecious (separate sexes) but sexes cannot be distinguished based on shell morphology. Larvae, called glochidia, are brooded in the gills by the female and are parasitic on catfishes. Known fish hosts are the Flathead Catfish, which does not occur in Canada, and the Channel Catfish, which does occur in Canada. Development on the fish host requires approximately 50-60 days. During this time, the larval mussel transforms to a juvenile, then drops off the fish host and grows to adult size and maturity. Like other freshwater mussels, Q. quadrula feeds on algae and bacteria filtered from the water column and bottom. Quadrula quadrula is a long-lived species with individuals from Manitoba living up to 64 years and averaging 22 years of age, with a generation time of roughly 20 years.

Population sizes and trends

In Ontario, Q. quadrula is restricted to a few coastal areas and rivers draining into Lake Huron, Lake Erie, Lake St. Clair, and Lake Ontario. A rough estimate for total population size in Ontario is at least 6 million individuals. The mussel community in this region is in decline with many species considered extirpated from areas they once occupied. Comparison with historical records indicates some reduction in the distribution of this species in Ontario. Recent studies indicate that Q. quadrula is abundant in some areas where it does occur and may be increasing its distribution within the Sydenham River, lower Thames River, and lower Grand River, but with current threats the overall trend may be a slow continuing decline over the next 3 generations.

In Manitoba, although the population size is estimated to range between roughly 1 million and 4 million, densities are generally low and appear to be in decline in some areas. The species occurs in the Red River and in the lower reaches of some of its tributaries, the Assiniboine River, and the lower reaches of some tributaries draining into Lake Winnipeg. Comparison with historical records of distribution indicates that the freshwater mussel community in Manitoba is in decline. Where Q. quadrula does occur in Manitoba it is never abundant with many fresh empty valves indicating high levels of recent mortality.

Threats and limiting factors

Like almost all North American freshwater mussels, this species is threatened by habitat loss and degradation and the effects of invasive species, particularly Zebra and Quagga mussels in Ontario. Zebra Mussels now threaten Q. quadrula in Manitoba, with Zebra Mussel populations becoming established in the Red River, Lake Winnipeg, and in reservoirs in the Red River watershed in North Dakota and Minnesota. Habitat changes associated with Zebra Mussels and modifications to the banks of the Red and Assiniboine rivers (e.g., rip-rap and dikes) that alter the flow hydrology of these rivers are threats. In both Ontario and Manitoba, Q. quadrula occurs in areas affected by industrial and municipal pollution and agricultural runoff.

Protection, status and ranks

Quadrula quadrula in both Ontario (Great Lakes - Upper St. Lawrencepopulation)and Manitoba (Saskatchewan - Nelson Rivers population) is listed under Schedule 1 of Canada’s Species at Risk Act. The act prohibits killing or capturing protected species, and protects critical habitat, when this has been described and approved. Populations in Ontario and Manitoba also are protected under each province’s endangered species act. Quadrula quadrula is considered to be stable in some U.S. states and critically imperilled in others, but in the majority of jurisdictions the species is unranked or ranks are under review. There are large populations in some U.S. Great Lakes states and it is not considered at risk in Michigan or Ohio.


Technical summary - Great Lakes - Upper St. Lawrence population

Scientific name:
Quadrula quadrula
English name:
Mapleleaf, Great Lakes - Upper St. Lawrence population
French name:
Mulette feuille d’érable - Population des Grands Lacs et du haut Saint-Laurent
Range of occurrence in Canada (province/territory/ocean):
Ontario

Demographic information

Demographic information
Summary itemsInformation
Generation time (usually average age of parents in the population; indicate if another method of estimating generation time indicated in the IUCN guidelines (2011) is being used).Estimate: 20 yrs.
Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?Yes. Projected decline of 3-30% based on cumulative threats identified in Threats Calculator.
Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations]Projected 3-30% decline over 3 generations; projected decline over 2 generations would be smaller.
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations].Estimated 12.5% decline in EOO over last 3 generations (i.e., since the invasion of the dreissenids); however, it is unlikely that this resulted in a similar percent decline in number of mature individuals because the species was never abundant in open waters of the Great Lakes. The locations with the largest number of mature individuals (Thames, Sydenham, and Grand rivers) currently appear stable.
[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations].Projected 3-30% decline based on Threats Calculator and projections for continued habitat degradation and continued competition from dreissenids. In addition, the IAO, EOO, and number of mature individuals will most likely decline if the subpopulations with small numbers of individuals (see below) are extirpated.
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future.Suspected 3-30% future decline; estimated 12.5% decline in EOO in the past which resulted in an unknown decline in number of mature mussels.
Are the causes of the decline a. clearly reversible and b. understood and c. ceased?a. No
b. Yes
c. No
Are there extreme fluctuations in number of mature individuals?No

Extent and occupancy information

Extent and Occupancy Information
Summary itemsInformation
Estimated extent of occurrence26,826 km2 based on minimum convex polygon.
Index of area of occupancy (IAO)
(Always report 2x2 grid value).
228 km2 discrete based on one grid over each observation record (57 2x2 km grids). 660 km2 continuous. Based on continuous stretch of river between all observation records (165 2x2 km grids).
Is the population “severely fragmented” i.e., is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?a. No
b. No
Number of “locations”
See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.
(use plausible range to reflect uncertainty if appropriate)
21 (or more) locations based on cumulative threats of agricultural, industrial, municipal pollution and impacts of dreissenid mussels: Ausable River, North Sydenham River, East Sydenham River, Thames River, Grand River, Welland River (+ Oswego River and Coyle Creek tributaries), Lake Ontario embayments (Jordan Harbour/Twenty Mile Creek, Sixteen Mile Creek, Fifteen Mile Creek/Pond, and Cootes Paradise), Ruscom River, Baptiste Creek, McGregor Creek, Bayfield River, St. Clair Delta, Lake Huron tributaries (Perch Creek/Tefler Diversion Channel, Cow Creek), Pelee Island (Lake Henry), Rondeau Bay.
Is there an [observed, inferred, or projected] decline in extent of occurrence?Yes - Projected 3-30%. See above boxes in Demographic information.
Is there an [observed, inferred, or projected] decline in index of area of occupancy?Yes - Projected 3-30%. See box above.
Is there an [observed, inferred, or projected] decline in number of subpopulations?Yes - Projected 3-30%. See box above.
Is there an [observed, inferred, or projected] decline in Number of “locations”
See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.?
Yes - Projected 3-30%. See box above. Subpopulation sizes at some locations may be very small (see Subpopulations box below).
Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?Yes - Projected. Habitat quality continues to decline due to pollution resulting primarily from agricultural runoff. Dreissenid mussels are also contributing to a projected decline in habitat quality.
Are there extreme fluctuations in number of subpopulations?No
Are there extreme fluctuations in Number of “locations”
See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.?
No
Are there extreme fluctuations in extent of occurrence?No
Are there extreme fluctuations in index of area of occupancy?No

Number of mature individuals (in each subpopulation)

Number of mature individuals (in each subpopulation)
Subpopulations (give plausible ranges)Estimated mature individuals
Ausable River10,000 - 180,000
North Sydenham River~25,000
East Sydenham River1,610,000 - 2,680,000
Thames River3,765,000 - 8,140,000
Grand River>325,000
Welland River (including Oswego River and Coyle Creek)Unknown (1000s)
Lake Ontario embayments (Jordan Harbour/Twenty Mile Creek, Sixteen Mile Creek, Fifteen Mile Creek/Pond, and Cootes Paradise)Unknown (1000s)
Ruscom RiverUnknown
Baptiste CreekUnknown
McGregor CreekUnknown, presumed small
Bayfield RiverUnknown, small (only 1 live animal collected)
St. Clair DeltaUnknown, small (only 1 live animal collected)
Lake Huron tributaries (Perch Creek/Tefler Diversion Channel, Cow Creek)Unknown, presumed small
Pelee Island (Lake Henry)Unknown, presumed small
Rondeau Bay (Lake Erie)Unknown, presumed small (only fresh shells collected)
TotalEstimated >6,000,000

Quantitative analysis

Quantitative analysis
Summary itemsInformation
Is the probability of extinction in the wild at least [20% within 20 years or 5 generations, or 10% within 100 years]?N/A - insufficient data for analyses

Threats (direct, from highest impact to least, as per IUCN Threats calculator)

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)
Summary itemsInformation
Was a threats calculator completed for this species?

Yes

  • Pollution: Habitat degradation from agriculture (siltation, loss of riparian vegetation, streambank erosion, and nutrient loading), municipal and industrial pollution (including oil spills).
  • Natural system modifications and invasive, non-native alien species: Invasive dreissenid mussel infestation may still be causing declines in some subpopulations. However, several river systems where Mapleleaf is found have little chance of becoming infested due to a lack of upstream impoundments that could act as seed populations for dreissenids.
What additional limiting factors are relevant?Abundance of host fish probably not an issue.

Rescue effect (immigration from outside Canada)

Rescue effect (immigration from outside Canada)
Summary itemsInformation
Status of outside population(s) most likely to provide immigrants to Canada.USA: Status apparently secure within most of US distribution, including populations on the US side of the Great Lakes.
Is immigration known or possible?Possible. Evidence of recent gene flow (Nm>1) between Canadian and US populations in Lake Erie drainage.
Would immigrants be adapted to survive in Canada?Likely. Habitats are nearly identical on both sides of the Great Lakes.
Is there sufficient habitat for immigrants in Canada?Yes
Are conditions deteriorating in Canada?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Yes, in places (see Threats).
Are conditions for the source population deteriorating?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Yes, in places (similar threats to Canadian subpopulations).
Is the Canadian population considered to be a sink?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
No
Is rescue from outside populations likely?Potentially, given the proximity of several large US populations and the high measured levels of current gene flow between the US and Canadian populations.

Data sensitive species

Data Sensitive Species
Summary itemsInformation
Is this a data sensitive species?No

Current status

Current status
Summary itemsInformation
Status HistoryDesignated Threatened in April 2006. Status re-examined and designated Special Concern in November 2016.

Status and reasons for designation

Status and reasons for designation
Summary itemsInformation
StatusSpecial Concern
Alpha-numeric codeNot applicable
Reasons for designationThis heavy shelled mussel, shaped like a maple leaf, has a limited distribution in southern Ontario. There is evidence of an ongoing, but slight, decline in the range over the last three generations. Low-impact threats, including those from Zebra and Quagga mussels, habitat alteration, and pollution continue. Despite these threats, this population is estimated to be large (millions of animals) and apparently stable at a number of locations in Lake St. Clair, Lake Erie, and western Lake Ontario watersheds. The change in status since the original report is a result of increased sampling effort across the region, newly discovered locations, and evidence for recent gene flow across Lake Erie, which suggests the potential for rescue.

Applicability of criteria

Applicability of criteria
Summary itemsInformation
Criterion A (Decline in Total Number of Mature Individuals)Does not meet criteria. Although the past rate of decline in EOO over the last 3 generations is 12.5% and a suspected decline of up to 30% over the next 3 generations is predicted by the threats assessment, these rates of decline are below threshold values.
Criterion B (Small Distribution Range and Decline or Fluctuation)Does not meet criteria. While the EOO (26,826 km2 from live individuals or fresh shells observed between 2000 and 2015) is above the threshold for Threatened (<20,000 km2: B1), the continuous IAO is below the threshold for Threatened (< 2,000 km2: B2). However, the species is not severely fragmented and is found at well more than 10 locations. There is a projected decline in EOO, IAO, habitat quality and number of locations and subpopulations, but the projected loss of several small-sized subpopulations/locations will result in only a minor decline in the number of mature individuals. The species does not undergo extreme fluctuations.
Criterion C (Small and Declining Number of Mature Individuals)Does not meet criteria. The number of mature individuals is unknown but estimated to be over 6 million and the largest subpopulations currently appear to be stable.
Criterion D (Very Small or Restricted Population)D1 is not applicable as the number of mature individuals is unknown but estimated to be over 6 million. Does not meet criteria for threatened D2 because both the IAO and number of locations are well above the typical thresholds (20 km2 and less than or equal to 5, respectively).
Criterion E (Quantitative analysis)Not applicable. Analyses have not been done.

Technical summary - Saskatchewan - Nelson Rivers population

Scientific name:
Quadrula quadrula
English name:
Mapleleaf, Saskatchewan - Nelson Rivers population
French name:
Mulette feuille d’érable, Population de la rivière Saskatchewan et du fleuve Nelson
Range of occurrence in Canada (province/territory/ocean):
Manitoba

Demographic information

Demographic information
Summary itemsInformation
Generation time (usually average age of parents in the population; indicate if another method of estimating generation time indicated in the IUCN guidelines (2011) is being used)Estimate: 20 yrs.
Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?Inferred and projected decline of 10-70% based on cumulative threats identified in Threats Calculator.
Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations]Projected 10-70% over 3 generations; projected decline over 2 generations should be similar because impact from invasive dreissenids would be larger soon after infestation.
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations].There has been an inferred decline in number of mature individuals based on 42.7% or 25.8% estimated declines in EOO and IAO over the last 3 generations, respectively. Confidence in these estimates is low based on limited sampling effort in the Red and Assiniboine rivers.
[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations].Projected 10-70% decline based on Threats Calculator.
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future.Suspected 10-70% future decline; past decline in EOO and IAO are 42.7 and 25.8%, respectively.
Are the causes of the decline a. clearly reversible and b. understood and c. ceased?a. No
b. Yes
c. No
Are there extreme fluctuations in number of mature individuals?No

Extent and occupancy information

Extent and occupancy information
Summary itemsInformation
Estimated extent of occurrence45,097 km2 calculated using a minimum convex polygon.
Index of area of occupancy (IAO)
(Always report 2x2 grid value).
92 km2 discrete based on one grid over each observation record (23 2x2 km grids). 1544 km2 continuous. Based on continuous stretch of river between all observation records (386 2x2 km grids).
Is the population “severely fragmented” i.e., is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?a. No
b. No
Number of “locations”
See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.
(use plausible range to reflect uncertainty if appropriate)
Between 11 and 7.
11 locations based on invasive species: Red River, La Salle River, Seine River, Rat River, Cooks Creek, Assiniboine River above Portage Diversion (dam), Assiniboine River below Portage Diversion, Brokenhead River, Wanipigow River, Bloodvein River, and Bradbury River based on threat from Zebra Mussels. 7 locations based on pollution: Red River (including Seine River, La Salle River, and Cooks Creek), Rat River, and Assiniboine River (above and below the Portage Diversion dam) each comprise single locations based on non-point source pollution inputs throughout their drainages (n=3); Brokenhead River, Wanipigow River, Bloodvein River, and Bradbury River represent 4 additional locations all of which drain into Lake Winnipeg separate from the Red River and are not subject to the same magnitude of pollution but would be separate locations based on invasive species.
Is there an [observed, inferred, or projected] decline in extent of occurrence?Yes. Observed decline of 42.7% over the last 3 generations. Confidence in this estimate is low based on limited sampling effort in the Red and Assiniboine rivers. Even with the threats of pollution and/or Zebra Mussel infestations, peripheral subpopulations could continue to persist for some time.
Is there an [observed, inferred, or projected] decline in index of area of occupancy?Yes. Observed decline of 25.8% over the last 3 generations. Confidence in this estimate is low based on limited sampling effort in the Red and Assiniboine rivers. Zebra Mussel infestation and/or pollution could further reduce IAO in the future.
Is there an [observed, inferred, or projected] decline in number of subpopulations?Unknown
Is there an [observed, inferred, or projected] decline in Number of “locations” ?
See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.?
Unknown
Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?Yes. Habitat quality continues to decline due to pollution resulting from agricultural runoff. Zebra Mussels will also contribute to a projected decline in habitat quality.
Are there extreme fluctuations in number of subpopulations?No
Number of “locations” ?
See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.
No
Are there extreme fluctuations in extent of occurrence?No
Are there extreme fluctuations in index of area of occupancy?No

Number of mature individuals (in each subpopulation)

Number of mature individuals (in each subpopulation)
Subpopulations (give plausible ranges)Estimated mature individuals
Red RiverUnknown
Assiniboine River (above Portage Diversion)Unknown
Assiniboine River (below Portage Diversion)estimated 1-4 million
Rat RiverUnknown
Brokenhead RiverUnknown
La Salle RiverUnknown
Cooks CreekUnknown
Bloodvein RiverUnknown
Bradbury RiverUnknown
Wanipigow RiverUnknown
Seine RiverUnknown
TotalUnknown, total population estimated at minimum 1-4 million individuals based on extrapolations from 2003-2004 data from the lower Assiniboine River.

Quantitative analysis

Quantitative analysis
Summary itemsInformation
Is the probability of extinction in the wild at least [20% within 20 years or 5 generations, or 10% within 100 years]?N/A - insufficient data for analyses.

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)
Summary itemsInformation
Was a threats calculator completed for this species?

Yes.

  • Invasive, non-native alien species and natural system modifications: Zebra Mussel infestation imminent or occurring at 8 of 11 locations in DU (except Wanipigow, Bloodvein and Bradbury rivers); rip rapping and diking for flood control.
  • Pollution: Habitat degradation from agricultural activity (siltation, loss of riparian vegetation, streambank erosion, and nutrient loading), municipal and industrial pollution.
What additional limiting factors are relevant?Abundance of host fish probably not an issue.

Rescue effect (immigration from outside Canada)

Rescue effect (immigration from outside Canada)
Summary itemsInformation
Status of outside population(s) most likely to provide immigrants to Canada.In same watersheds as Canadian population (Red River) it is either not ranked or is S3 or is in the same state of decline as Canadian population.
Is immigration known or possible?Possible
Would immigrants be adapted to survive in Canada?Likely, but needs to be confirmed by testing.
Is there sufficient habitat for immigrants in Canada?Yes
Are conditions deteriorating in Canada?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Yes
Are conditions for the source population deteriorating?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Unknown, but probable.
Is the Canadian population considered to be a sink?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
No
Is rescue from outside populations likely?Unknown, but possible.

Data sensitive species

Data Sensitive Species
Summary itemsInformation
Is this a data sensitive species?No

Current status

Current status
Summary itemsInformation
Status HistoryDesignated Endangered in April 2006. Status re-examined and designated Threatened in November 2016.

Status and reasons for designation:

Status and reasons for designation:
Summary itemsInformation
Status:Threatened
Reasons for designationThis heavy-shelled mussel has a small range and few locations, and occurs in habitat projected to continue to decline in quality. Present and ongoing threats include pollution from agricultural effluent, urban wastewater, and industrial sources. The arrival and establishment of invasive Zebra Mussels in 2013 represents a new threat of likely high severity. This change in status is a result of new surveys revealing previously unknown locations.

Applicability of criteria

Applicability of criteria
Summary itemsInformation
Criterion A (Decline in Total Number of Mature Individuals)Does not meet criteria. The actual rate of decline in EOO and IAO over the past 3 generations is uncertain. The threats assessment projects a suspected decline of between 10 and 70% in the next 3 generations, with the uncertainty resulting from the impacts of the invasive Zebra Mussel.
Criterion B (Small Distribution Range and Decline or Fluctuation)While the EOO (45,097 km2 - from live individuals or fresh shells observed between 2000 and 2015) is above the threshold for Threatened (< 20,000 km2: B1), the actual IAO lies between 92 km2 (discrete) and 1544 km2 (continuous) and is below the threshold for either Endangered (< 500 km2) or Threatened (< 2,000 km2: B2). The species is not severely fragmented and does not undergo extreme fluctuations; however, there are between 7 and 11 locations, with the lower number being below the threshold for Threatened (10 or fewer locations). IAO and number of mature individuals are expected to decline due to the continuing decline in habitat quality.
Criterion C (Small and Declining Number of Mature Individuals)
Does not meet criteria. Number of mature individuals is unknown but estimated to be a minimum of 1-4 million.
Criterion D (Very Small or Restricted Population)D1 is not applicable as the number of mature individuals is unknown but estimated to be a minimum of 1-4 million. D2 Threatened is not applicable because both the IAO and number of locations exceed the typical thresholds (20 km2 and less than or equal to 5, respectively). While the species is prone to the effects of human activities or stochastic events, the species is not expected to meet the thresholds for Critically Endangered within 1 or 2 generations (20-40 years) or become extirpated once these activities or events occur.
Criterion E (Quantitative analysis)Not applicable. Analyses have not been done.

Preface

Since the first COSEWIC (2006) status report on Mapleleaf (Quadrula quadrula), a great deal of new distributional data have been collected on the Great Lakes - Upper St. Lawrence Designatable Unit (DU). There have been new occurrences (= locations) discovered in several coastal embayments and drowned river mouths in Lake Ontario, small tributaries of Lake Huron in Lambton County near Sarnia, and a rediscovery of live animals in the Welland River and its tributaries. With the new data incorporated into the distribution for the Great Lakes - Upper St. Lawrence DU, there has been little apparent change in extent of occurrence (EOO) and index of area of occupancy (IAO) and the number of locations is at least 21. Threats in the Great Lakes - Upper St. Lawrence DU remain similar to what was described in the original report: infestation by dreissenid mussels and pollution from agricultural runoff (in riverine systems); however, both of these threats are perhaps not as severe as first feared. For the Saskatchewan - Nelson Rivers DU there are new records of live animals in tributaries of the Red River and of Lake Winnipeg, thus increasing the number of potential locations in comparison to the original report (COSEWIC 2006). The historical data collected in Manitoba have a great deal of uncertainty due to limited sampling effort in the large river systems where Mapleleaf has been found historically, thus making it difficult to confidently determine trends in EOO and IAO. The only other major change for the Saskatchewan-Nelson Rivers DU since the original status report is that Zebra Mussels (Dreissena polymorpha) have become established in Lake Winnipeg, the Red River, and upstream of the Canadian occurrences in reservoirs in the Red River watershed in North Dakota and in tributaries of the Red River in Minnesota. The presence of Zebra Mussel in these systems represents an active and ongoing threat as well as a projected threat in the Assiniboine River as these invasive mussels will undoubtedly spread.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2016)

Wildlife species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.
Extinct (X)
A wildlife species that no longer exists.
Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered (E)
A wildlife species facing imminent extirpation or extinction.
Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.
Special concern (SC)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.
Not at risk (NAR)
(Note: Formerly described as “Not in any category”, or “No designation required.”)
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.
Data deficient (DD)
(Note: Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.


Wildlife species description and significance

Name and classification

Scientific name: Quadrula quadrula (Rafinesque, 1820)

English common name: Mapleleaf

French common name: Mulette feuille d’érable

The current authority for the classification and scientific nomenclature of freshwater mussels in North America is Turgeon et al. (1998). The classification currently accepted is:

Phylum: Mollusca

Class: Bivalvia

Subclass: Palaeoheterodonta

Order: Unionoida

Superfamily: Unionoidea

Family: Unionidae

Subfamily: Ambleminae

Tribe: Quadrulini

Genus: Quadrula

Species: Quadrula quadrula

A complete list of synonymies and the nomenclatural history for Quadrula quadrula is provided by Parmalee and Bogan (1998).

Morphological description

Mapleleaf (Quadrula quadrula) is a medium to large freshwater mussel that can be recognized by two bands of nodules radiating in a v-shape from the umbo (the beak that protrudes above the hinge of each valve) to the ventral margin (Figure 1). One band is located centrally and the other is located on the posterior ridge. The rows are separated by a shallow groove. The following species’ description has been adapted from Clarke (1981), Cummings and Mayer (1992), Parmalee and Bogan (1998), Graf and Ó Foighil (2000), Cicerello and Schuster (2003), Haag and Staton (2003), and Hay et al. (2003). The morphology of Canadian specimens is consistent with the range of variation reported from specimens from the United States. The conchological morphology of sexes is alike. The shell is thick, moderately inflated, and quadrate in outline. The anterior end is rounded, the posterior end is squared or truncated. Umbos are small and slightly raised above the hinge line. The umbo is sculptured; double loops or zigzags radiate to the ventral margin as two rows of raised nodules. Nodules on the umbo are small and crowded, and are generally eroded on older specimens. Nodules distal to the umbo may be elongated or rounded. Nodules radiating from the umbo are separated by a wide, shallow sulcus or furrow. Typically, one row of nodules is centrally located, the other posteriorly. Occasional variations in nodule patterns range from small nodules scattered over shell surface to absent (Neel 1941). Periostracum is variable, ranging from yellowish green to light brown in young individuals, with older individuals ranging from greenish brown through dark brown. Annual growth lines on the shell surface are obvious and well defined, especially in younger individuals; they can be crowded and difficult to distinguish at the shell margin of older individuals.

Pseudocardinal teeth are well developed, vertically elongated and serrated; there are two in the left valve, one in the right (Figure 2). The pseudocardinal tooth in the right valve is heavy, thick and triangular. Pseudocardinal teeth in the left valve are rough, solid and sometimes joined dorsally. Two lateral teeth in the left valve are erect, fairly long and straight, and may be serrated. The single lateral tooth in the right valve is high, long and straight, and may be serrated. The interdentum is wide. The beak (umbo) cavity is deep but open. The nacre is white and iridescent posteriorly.

Parmalee and Bogan (1998) report mature Q. quadrula reaching 120 mm in length. In Canada, Clarke (1981) reports Q. quadrula reaching 125 mm in length (135 mm according to Morris unpubl. data), 100 mm in height, and 50 mm in width. In Manitoba, individuals have been recorded up to 121 mm in length, 88 mm in height, and 52 mm in width (Carney 2003a).

In Ontario, Q. quadrula is most similar to Quadrula pustulosa (Pimpleback - Low Priority COSEWIC Mollusc Species Specialist Subcommittee candidate) and Cyclonaias turberculata (Purple Wartyback - COSEWIC candidate species in fall 2017 Call for Bids). These can be distinguished as follows. Quadrula quadrula has nodules restricted to two bands that extend to the beak whereas they are scattered and more uniformly distributed on Q. pustulosa and do not extend to the beak. Quadrula quadrula is quadrate in outline whereas Q. pustulosa is rounded in outline. Quadrula pustulosa also has a prominent green ray extending from the beak, that is lacking in Q. quadrula. Cyclonaias tuberculata has a large number of small pustules extending from the beak through the ventral margin to the posterior of the shell; however, these are not in rows as they are in Q. quadrula. The nacre in C. tuberculata is distinctly purple but white in Q. quadrula. Juvenile C. tuberculata can be especially difficult to distinguish from juvenile Q. quadrula. There are no other mussels in Canada with which Q. quadrula can be confused.

The following description of soft-tissue morphology is derived from Lydeard et al. (1996) and Graf and Ó Foighil (2000). Quadrula quadrula uses all four gill demibranchs as marsupia. The interlamellae of gill demibranchs are connected by complete septa. The marsupial water tubes are undivided, not tripartite. There is no swelling of the marsupial interlamellar septa into water tubes. The margin of the gravid marsupium is sharp. The ventral margin of the marsupium does not extend beyond the non-marsupial portion of the gill. The mantle ventral to the incurrent siphon is simple and is not modified with papillae or lure-like elaborations.

Figure 1. Line drawing showing Quadrula quadrula external shell morphology.
Line drawing showing Quadrula quadrula external shell morphology
Photo: © after Cummings and Mayer 1992
Long description for Figure 1

Illustration of the external shell morphology of the Mapleleaf. This medium to large freshwater mussel can be recognized by two bands of nodules radiating in a v-shape from the umbo to the ventral margin. One band is located centrally and the other is located on the posterior ridge. The rows are separated by a shallow groove.

Figure 2. Line drawing showing Quadrula quadrula left valve internal shell morphology.
Line drawing showing Quadrula quadrula left valve internal shell morphology
Photo: © after Cummings and Mayer 1992
Long description for Figure 2

Illustration of the left valve internal shell morphology of the Mapleleaf. The left valve bears two well developed, vertically elongated and serrated Pseudocardinal teeth. The two lateral teeth are erect, fairly long and straight, and may be serrated. The interdentum is wide and the umbo cavity is deep but open.

Population spatial structure and variability

Davis (1984) and Johnson et al. (1998a,b,c) used allozyme electrophoresis to describe genetic variation in populations of Q. quadrula from Wisconsin and Arkansas, respectively. They described similar alleles per locus (1.6) and mean polymorphism (0.35-0.36) for these populations. In contrast, the mean in the Wisconsin population was almost twice that in the Arkansas population. These data are in contrast to those reported by Berg et al. (1998) who investigated allozyme variation in Q. quadrula populations from Ohio and the lower Mississippi and found much higher values for mean polymorphism, mean heterozygosity, and alleles per locus than reported by Davis (1984) and Johnson et al. (1998a,b,c). Berg et al. (1998) also reported much lower values for Fst and Nei’s genetic distance than reported by Johnson et al. (1998a,b). These genetic distance data indicate there is very little genetic variation among the Q. quadrula populations examined by Berg et al. (1998) despite being separated by up to 2,000 km of river. Berg et al. (1998) suggested this may be a consequence of high gene flow resulting from using a highly vagile host for the glochidia (see BIOLOGY: Life Cycle and Reproduction).

Preliminary analysis (Figure 3) of unpublished data (Levine pers. comm. 2004; Zanatta unpubl. data) on the COI gene region of Q. quadrula populations from regions in the United States and from Ontario and Manitoba reveals that the Ontario and Manitoba populations share the majority of their haplotypes with some populations in the United States. This suggests the Canadian populations are subsets derived from the American populations in the Mississippi River drainage. Both the Ontario and Manitoba populations appear to have low haplotype diversity. However, both populations have haplotypes that are unique and not shared with any other region. This indicates there is unique genetic information in each of the Ontario and Manitoba populations.

The genetic population structure of Q. quadrula in the Great Lakes region has been thoroughly studied since the previous COSEWIC (2006) report. Galbraith et al. (2015) found substantial genetic diversity of Q. quadrula sampled from the Sydenham, Thames, and Grand rivers with high allelic richness and heterozygosity at eight microsatellite loci. Genetic structure for Q. quadrula was primarily evident among the rivers: the genetic populations of Q. quadrula showed evidence of partitioning between the Sydenham and the Grand and Thames sites, with the latter two rivers falling out as a single population (Galbraith et al. 2015). Paterson et al. (2015) showed clear evidence of gene flow among sample sites, low-level population divergence, and clear isolation-by-distance in coastal areas of western Lake Erie (US side of the lake), the Maumee River and the Grand River (Ontario). On a larger spatial scale, analyses of microsatellite DNA genotypes show that Q. quadrula likely entered the Great Lakes at the end of the Pleistocene glaciation via a single route by way of a connection between the Illinois River system (upper Mississippi River drainage) and Lake Michigan, with subsequent dispersal across the Great Lakes region and represent a single genetic population with high levels of gene flow [number of migrants per generation (Nm) >1, Zanatta unpubl. data]. Furthermore, it appears that the subpopulations of Q. quadrula in Lake Ontario may have become established recently (last 200 years) with their dispersal into the lake being facilitated by the construction of the Welland Canal (Hoffman and Zanatta unpubl. data).

Figure 3. Haplotype distributions for Quadrula quadrula subpopulations determined from the cytochrome oxidase I gene of the mitochondrial genome. Shaded area indicates the North American distribution of Q. quadrula.
Haplotype distributions for Quadrula quadrula subpopulations
Photo: © map from Parmalee and Bogan 1998
Long description for Figure 3

Map illustrating haplotype distributions (pie charts) among North American subpopulations of the Mapleleaf. Shading indicates the North American distribution of the Mapleleaf, which occurs throughout the Ohio-Mississippi River drainages extending southeast to Louisiana, southwest to eastern Texas, and northwest to Minnesota. It is present in the Red River drainage in North Dakota, Minnesota, and Manitoba. In the Great Lakes drainage it has been recorded from the Lake Huron, Lake Erie, Lake St. Clair, and Lake Ontario drainages.

Designatable units

COSEWIC can recognize units below the species level as designatable units (DUs). The populations of Q. quadrula in Ontario and Manitoba merit distinction as separate designatable units because they are discrete and evolutionarily significant. They satisfy the three criteria for discreteness: occupation of different COSEWIC Freshwater Biogeographic Zones, natural disjunction, and genetic distinctiveness. First, they occupy biogeographically distinct freshwater biogeographic zones. The Ontario population occupies the Great Lakes-Upper St. Lawrence National Freshwater Biogeographic Zone whereas the Manitoba population occupies the Saskatchewan-Nelson Rivers National Freshwater Biogeographic Zone. Second, they are separated by a major range disjunction. The Ontario population is part of the Great Lakes-St. Lawrence watershed and the Manitoba population is part of the Hudson Bay watershed. As aquatic organisms, they and their host fish are limited to dispersal only within these continental scale watersheds. Effectively this means they are isolated and disjunct from each other and from other North American Q. quadrula populations in the Ohio-Mississippi watershed in the United States. Third, they can be recognized as being genetically distinct. Despite being low in genetic diversity and the majority of individuals sharing a haplotype common throughout North American populations, each population has unique haplotypes. Ontario subpopulations have two distinct haplotypes and Manitoba subpopulations have three distinct haplotypes. Evolutionary significance also is demonstrated by the genetic differences which may indicate local evolutionary adaptation to the different Freshwater Biogeographic Zones, as has been used for freshwater fishes. Two DUs for Q. quadrula were previously recognized (COSEWIC 2006), and were named Great Lakes-Western St. Lawrence population and Saskatchewan-Nelson population. These formal names are herein changed to reflect the COSEWIC Freshwater Biogeographic Zones; however, the different DUs may also be referred to as the Ontario and Manitoba populations, respectively in this report.

Special significance

There are 20 recognized species in the genus Quadrula of which one is considered extinct and four are considered endangered in the United States (Williams et al. 1993). Many of the remaining species are considered vulnerable to critically imperilled in most of their ranges (NatureServe 2016). Two species of the genus, Q. pustulosa and Q. quadrula, are recorded from Canada. Quadrula quadrula is the most widespread species of the genus and, in Canada, is present in southwestern Ontario and Manitoba. Quadrula quadrula currently appears to be the most stable, in much of its distribution, of all the species in the genus. Considering the state of the members of the genus, Q. quadrula may represent the best opportunity to maintain representation of the genus Quadrula over the long term. Canadian populations occur in separate continental watersheds that are separate from the main distribution of this species and have unique haplotypes and ecological information important in conserving the diversity of the species.

Distribution

Global range

Quadrula quadrula (type locality Ohio River) is distributed throughout the Ohio-Mississippi River drainages extending southeast to Louisiana, southwest to eastern Texas, and northwest to Minnesota (Clarke 1981; Parmalee and Bogan 1998; Figure 3). It is present in the Red River drainage in North Dakota, Minnesota, and Manitoba (Clarke 1981; Cvancara 1983). In the Great Lakes drainage it has been recorded from the Lake Huron, Lake Erie, Lake St. Clair, and Lake Ontario drainages. In the United States Q. quadrula has been reported from Alabama, Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Missouri, Mississippi, North Dakota, Nebraska, New York, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Wisconsin, and West Virginia (Parmalee and Bogan 1998; NatureServe 2016).

Canadian range

In Canada, Q. quadrula has been reported only from Ontario and Manitoba (Figure 3). In Ontario (Figures 4 and 5), Q. quadrula has been reported from Lake St. Clair, Lake Erie, and the Niagara River and their tributaries: Baptiste Creek, and the Grand, Thames, Ruscom, Sydenham, and Welland rivers. It is also found in tributaries of southern Lake Huron including the Ausable River, Bayfield River, Perch Creek/Tefler Diversion Channel, and Cow Creek. Live Q. quadrula were found in Jordan Harbour/Twenty Mile Creek, Cootes Paradise (Hamilton Harbour), Fifteen Mile Creek/Pond, and Sixteen Mile Creek, which are drowned rivermouths in western Lake Ontario. In Manitoba (Figures 6 and 7), Q. quadrula has been recorded from the Assiniboine River, Bloodvein River, Bradbury River, Brokenhead River, Cooks Creek, LaSalle River, Rat River, Red River, Roseau River, Seine River, and Wanipigow River.

Extent of occurrence and area of occupancy

The current (2000-2015) extent of occurrence (EOO) for the Great Lakes - Upper St. Lawrence population, calculated using the minimum convex polygon, around sites with live or fresh dead shells is 26,826 km2 (Figure 5). The total EOO, including all records both historical (prior to 2000) and current (2000-2015) is 32,940 km2 (Figure 4); this assumes that the rangehas not expanded since 2000 and that the new occurrence records are a result of sampling effort (see next section). Contraction of the range through losses of subpopulations from the Detroit and Niagara rivers and along the south shore of Lake St. Clair has resulted in a calculated 12.5% decrease in EOO. The current discrete IAO, as calculated by occupancy (of live or fresh dead shells) in each 2 x 2 km grid, is 228 km2 (Table 1, Figure 5); an identical 228 km2 discrete IAO is calculated from all records collected before 2000. This apparent similarity is again the result of newly discovered subpopulations and hides the loss of previously occupied grid squares. The current continuous IAO is 660 km2 (calculated by joining intervening 2 x 2 km grid cells along occupied river systems but excluding the open waters of the Great Lakes where dreissenid mussel [Zebra Dreissena polymorpha and Quagga D. bugensis] infestation densities are high).

Figure 4. Total distribution of Quadrula quadrula in Ontario based on records and surveys prior to and after 2000 reported in the Lower Great Lakes Unionid database. The total calculated extent of occurrence (historical plus current) is shown.
Total distribution of Quadrula quadrula in Ontario
Long description for Figure 4

Map of the distribution of the Mapleleaf in Ontario based on records and surveys prior to 2000 and from 2000 to 2015, reported in the Lower Great Lakes Unionid database. The extent of occurrence (32,940 square kilometres) is shown in outline.

Figure 5. Current distribution of Quadrula quadrula in Ontario based on records and surveys from 2000-2015 reported in the Lower Great Lakes Unionid database. The Bayfield River is the northwestern most dot.
Figure 5. Current distribution of Quadrula quadrula in Ontario based on records and surveys from 2000-2015
Long description for Figure 5

Map of the current distribution of the Mapleleaf in Ontario based on records and surveys from 2000 to 2015 reported in the Lower Great Lakes Unionid database. Current extent of occurrence (outline) and index of area of occupancy (grid cells) are also shown.

Table 1. Index of area of occupancy (IAO) based on 2 x 2 km grid placed over the occurrence records of Quadrula quadrula in Ontario collected since 2000.
LocationsIndex of area of occupancy (km2)
Ausable River20
North Sydenham River4
East Sydenham River32
Thames River28
Grand River44
Welland River20
Coyle Creek4
Oswego River4
Jordan Harbour/Twenty Mile Creek16
Sixteen Mile Pond4
Fifteen Mile Creek/Pond4
Cootes Paradise/Spencer Creek4
Ruscom River8
Baptiste Creek4
McGregor Creek4
Bayfield River4
St. Clair Delta4
Perch Creek/Tefler Diversion Channel8
Cow Creek4
Lake Henry (Pelee Island)4
Rondeau Bay (Lake Erie)4
TOTAL IAO228

Comparing historical and current (2000-2015) distribution in Manitoba also is confounded by newly discovered subpopulations and the lack of resurveying previously occupied sites. The current distribution in Manitoba has apparently declined in comparison to that recorded historically (Clarke 1973; Pip pers. comm. 2004; Watkinson pers. comm. 2015; Morris unpubl. data) (Figures 6 and 7). Using a minimum convex polygon of sites with live or fresh dead shells, the current (2000-2015) EOO is approximately 45,097 km2 (Figure 7) as compared with 78,755 km2 calculated using all records collected prior to 2000: an apparent decline of 42.7%. The current discrete IAO (occupied 2 x 2 km grid squares with live or fresh dead shells) is estimated to be 92 km2 (Table 2; Figure 7), as compared to a historical discrete IAO of 124 km2 calculated using all records collected prior to 2000: a 25.8% decline. The current continuous IAO (following the occupied river systems) is 1544 km2. The continuous IAO does not include open waters of Lake Winnipeg where Q. quadrula has not been reported in recent years and where Zebra Mussels have recently become established (see Threats). It is recognized that sampling effort may not have been sufficient to determine if there has in fact been a decline in EOO or IAO with the apparent contraction in EOO being from not recently finding the species either along the Assiniboine River upstream of Brandon or along the west-central shore of Lake Winnipeg; however, neither of these areas has been resurveyed. The calculated declines are based on the available data. The decline in IAO may be more reliable due to the apparent disappearance of the species from Lake Winnipeg.

Figure 6. Historical distribution of Quadrula quadrula in Manitoba based on records and surveys prior to 1992. The Shellmouth Reservoir is the northwestern-most dot.
Historical distribution of Quadrula quadrula in Manitoba based on records and surveys prior to 1992
Photo: © reported by Clarke (1973) and Pip (pers. comm. 2004)
Long description for Figure 6

Map of the historical distribution of the Mapleleaf in Manitoba based on records and surveys prior to 1992 reported by Clarke (1973) and Pip (pers. comm. 2004).

Figure 7. Current distribution and calculation of extent of occurrence and index of area of occupancy of Quadrula quadrula in Manitoba based on surveys from 2000-2015. Cooks Creek flows into the Red at Selkirk, before the Red flows into Lake Winnipeg. The following rivers with records of Q. quadrula are found along the eastern edge of Lake Winnipeg (south to north): Brokenhead, Wanipigow, Bloodvein (2 dots and square), and Bradbury rivers. The La Salle River (triangle and superimposed dots) flows into the Red River south of Winnipeg.
Current distribution and calculation of extent of occurrence and index of area of occupancy of Quadrula quadrula in Manitoba
Long description for Figure 7

Map of the distribution of the Mapleleaf in Manitoba based on surveys from 2000 to 2015. Current extent of occurrence (outline) and index of area of occupancy (grid cells) are also shown.

Table 2. Index of area of occupancy (IAO) based on 2 x 2 km grid placed over the occurrence records of Quadrula quadrula in Manitoba collected since 2000.
LocationsIndex of area of occupancy (km2)
Assiniboine River (above Portage diversion)16
Assiniboine River (below Portage diversion)20
Red River12
Brokenhead River12
Cooks Creek4
Rat River4
La Salle River4
Wanipigow River4
Bloodvein River8
Bradbury River4
Seine River4
TOTAL IAO92

Search effort and distribution of quadrula quadrula in Ontario

The Lower Great Lakes Unionid Database was used to identify occurrence records for Q. quadrula in Ontario. The database is continually updated with the results of new surveys by Dr. Todd Morris and his team at Fisheries and Oceans Canada (DFO) as well as surveys elsewhere in Ontario by other organizations (e.g., Ontario Ministry of Natural Resources and Forestry - MNRF). The database currently consists of more than 10,000 records for 40 species collected from more than 2,500 sites throughout the Lake Ontario, Lake Erie, Lake St. Clair, and lower Lake Huron drainage basins since 1860. For a detailed description of the database and its historical data sources, see Metcalfe-Smith et al. (1998a).

Quadrula quadrula was historically collected from the Detroit, Sydenham, Thames, Grand, Welland, and Niagara rivers as well as Lake Erie and Lake St. Clair. The earliest known records of the species in each of these waterbodies were as follows: between the 1880s and 1930s by various surveyors for the Detroit River (Schloesser et al. 2006), 1963 by H.D. Athearn for the Sydenham River near Shetland, 1894 by J. Macoun for the Thames River near Chatham, 1885 by J. Macoun for the Grand River near Cayuga, 1983 by D.J. Berg for the Welland River in Welland, 1934 by J.P. Oughton for the Niagara River, 1894 by J. Macoun for Lake Erie at Rondeau Bay, and 1965 by C.B. Stein for Lake St. Clair near the mouth of the Thames River. Figure 4 shows the total distribution of Q. quadrula in Ontario including the historical distribution based on 106 records collected between 1885 and 2000. The current distribution of the species is shown in Figure 5 and is based on 1647 records (live animals) collected between 2000 and 2015 (i.e., within the last generation for Q. quadrula).

Populations of Q. quadrula and other species of freshwater mussels in the Canadian and U.S. waters of the lower Great Lakes and connecting channels have been almost entirely lost due to the impacts of dreissenid mussels. Small isolated populations of native mussels can still be found in some coastal areas where densities of dreissenids have remained low (e.g., Nichols and Wilcox 1997; Zanatta et al. 2002; McGoldrick et al. 2009; Crail et al. 2011; Zanatta et al. 2015, Morris unpubl. data). In the Detroit River, less than 10% of the unionid population and only 13 of 24 species present prior to the dreissenid invasion survived to 1994 (Schloesser et al. 1998). Only five living mussels were found during follow-up surveys at several sites in 1998 (Schloesser et al. 2006) and none was Q. quadrula. Nalepa et al. (1996) surveyed 29 sites in the offshore waters of Lake St. Clair in 1986, 1990, 1992, and 1994. Quadrula quadrula was found alive at one site in U.S. waters in both 1986 and 1990 but not during later surveys. Gillis and Mackie (1994) surveyed an area off the mouth of the Puce River on the southwestern shore of Lake St. Clair between 1990 and 1992. The number of species found declined from 11 in 1990 to four in 1991 and no live mussels were found in 1992. They did not find any Q. quadrula during their surveys. Zanatta et al. (2002) surveyed 95 sites in nearshore areas around Lake St. Clair between 1999 and 2001 and found one Q. quadrula at a site near the mouth of the Thames River in 1999. Metcalfe-Smith et al. (2004) surveyed 28 sites in Canadian and U.S. waters of the Lake St. Clair delta in 2003 and did not find any live Q. quadrula. One live animal was subsequently collected from the delta in 2005 but none since (McGoldrick et al. 2009). Quadrula quadrula was reported from Rondeau Bay on the north shore of Lake Erie in 1894 and 1961, but only old weathered shells were found during a survey in 2001 (Zanatta unpubl. data). Additional sampling in 2014 and 2015 by the Ontario MNRF at 15 sites (4.5 person-hours of search effort at each site) in Rondeau Bay revealed four live unionid species including large numbers of Giant Floater (Pyganodon grandis); two fresh shells of Q. quadrula were found (Reid et al. 2016). There are records for Q. quadrula from Pelee Island in 1962, 1978, and 1985 and shells were collected in 1992. Although there have been no further surveys around Pelee Island, 19 sites around the nearby Bass Islands (U.S. waters, a few kilometres south of Pelee Island) were surveyed in 1998 and no live unionids were found (Ecological Specialists Inc. 1999). One site on South Bass Island had supported 27 live species of mussels in 1960. An informal Ontario MNRF survey of Lake Henry (a coastal embayment) at the north end of Pelee Island found two live Q. quadrula in summer 2015 (Cairns pers. comm. 2015). There are two historical records for Q. quadrula from the Niagara River. Thirteen sites were surveyed in 2001 for the New York Power Authority. Old shells of 16 species were found and one site had living animals of three species; unfortunately, the consultant who did the survey was unable to disclose the names of the species found alive (Schneider pers. comm. 2002). Additional (limited) sampling on the US side of the Niagara River in 2011 did not recover any living Q. quadrula (Zanatta et al. 2015). Live Q. quadrula were confirmed in the Welland River in 2008 with 25 live animals collected from a single site near Warner in the Niagara Region, Ontario (Morris et al. 2012a). The same site on the Welland River was revisited in 2014 and searched for 12.5 person-hours, yielding 58 live Q. quadrula (Hoffman unpubl. data) and additional live specimens were collected in 2015 from Coyle Creek and the Oswego River (Welland River tributaries, Morris unpubl. data).

In 2010, Q. quadrula was discovered in Jordan Harbour, a coastal embayment of western Lake Ontario. Additional suveys in 2011, 2013, 2014, and 2015 have confirmed a large number of live animals in Jordan Harbour/Twenty Mile Creek and live specimens from additional Lake Ontario coastal embayments: Sixteen Mile Creek, Fifteen Mile Creek/Pond, and Cootes Paradise/Spencer Creek (Hamilton Harbour) (Reid et al. 2014; Minke-Martin et al. 2015; Ontario MNRF unpubl. data; McNichols-O’Rourke and Morris unpubl. data).

According to Metcalfe-Smith et al. (2003), Q. quadrula was encountered more frequently in the Sydenham River during 1999-2004 surveys than in the past (pre-1991). It was found at 56% of 16 sites surveyed in 1997-1999 vs. 30% of 23 sites surveyed in the same reaches between 1929 and 1991. Intensive survey work on the Sydenham River has continued and by the end of 2004 a total of 18 sites had been sampled semi-quantitatively and 15 sites quantitatively (13 sites were sampled using both techniques). The range of Q. quadrula in the east branch of the Sydenham River is now known to extend from Tupperville to approximately 10 km upstream of Alvinston. Many successful sampling sites along this stretch of the Sydenham River were re-sampled from 1997 to 2015 and continually yielded Q. quadrula (Metcalfe-Smith and Zanatta 2003; Bouvier and Morris 2010; Morris unpubl. data). Quadrula quadrula has been found more sporadically in the north branch of the Sydenham River (Bear Creek) from Petrolia downstream to Wallaceburg (Metcalfe-Smith and Zanatta 2003).

There are only scattered historical records available for mussels in the Thames River. However, Q. quadrula was reported from several sites in the middle and lower reaches in 1894, 1934, 1963, 1973, 1985, and 1991-92. The river was extensively surveyed in the 1990s and 2000s. Morris (1996) surveyed 30 sites in 1994, focusing on the smaller tributaries, and found Q. quadrula at one site on McGregor Creek in Chatham. Metcalfe-Smith et al. (1998b, 1999) surveyed 16 sites, mainly on the main stem, in 1997-98 and observed the species at seven sites in the lower part of the watershed. Morris surveyed 25 sites in the Upper Thames River above Delaware in 2004 and did not find Q. quadrula at any site. In 2005, Morris returned to the lower Thames River and found Q. quadrula at 10 sites. Although his data do not extend the range in the Thames they do fill some previous gaps in coverage and show that most of the lower Thames is occupied by Q. quadrula (Morris and Edwards 2007). The available data do not indicate any change over time in the distribution of Q. quadrula in the Thames River.

Live Q. quadrula have been found in the Ruscom River, a tributary of Lake St. Clair, and Baptiste Creek, a tributary of the lower Thames River where nine specimens were found in 2011 surveys (McNichols-O’Rourke et al. 2012). In the Ruscom River, Q. quadrula was first discovered by Zanatta (2000) in 1998 in limited surveys. Additional surveys by DFO yielded 26 live specimens at two of six sites in 2010 (McNichols-O’Rourke et al. 2012).

The Grand River is one of the best studied watersheds for mussels in Ontario, with nearly 1,000 records available from 1885-2014. Collections have been made in nearly every decade. Major surveys were conducted in 1970-72 (68 sites, Kidd 1973) and in 1995 and 1997-98 (94 sites, Metcalfe-Smith et al. 2000a). There have been no changes over time in the distribution of Q. quadrula in the Grand River; it has always occurred in the lower 50 km of the river between Caledonia and Port Maitland. Numerous live specimens were found above the dam in Dunnville in 2008 (Paterson et al. 2015). In 2011, five sites were surveyed in the lower Grand River and Q. quadrula was found alive at all sites (McNichols-O’Rourke et al. 2012). Live specimens were again collected in 2014 below the dam in Dunnville (Hoffman unpubl. data; Minke-Martin et al. 2015).

Quadrula quadrula can also be found in some southern Lake Huron tributaries. Detweiler (1918) surveyed the Ausable River in 1916 primarily for thick-shelled species that could be used in the pearl button industry. There are also records from 1929 and 1950 for a site near Hungry Hollow in the lower portion of the watershed and Morris and Di Maio (1998-1999) surveyed six sites on the river in 1993-94. Quadrula quadrula was not among the 14 species found during these surveys. Metcalfe-Smith et al. (unpubl. data) surveyed 25 sites throughout the river from 1998-2004 and found 23 species of mussels alive including Q. quadrula, which was restricted to four sites in a short stretch of the lower main stem of the river. Additional quadrat surveys by the Ausable Bayfield Conservation Authority (ABCA) and DFO between 2009 and 2013 confirm this distribution in the Ausable River (ABCA unpubl. data; Bouvier and Morris 2010). One live specimen was found at the mouth of the Bayfield River in 2007 during an extensive bioblitz of the watershed (Morris et al. 2012b). Surveys in 2014 of two small tributaries (Perch Creek/Tefler Diversion Channel and Cow Creek) draining into southern Lake Huron near Sarnia reported 24 live Q. quadrula (Carroll unpubl. data). These are new records of previously unsurveyed streams in the Lake Huron watershed. Surveys of the Maitland and Saugeen river watersheds failed to find any evidence of Q. quadrula (McNichols-O’Rourke et al. 2012) and it seems unlikely that Q. quadrula ever occurred in the lower Lake Huron drainage north of the Bayfield River.

Search effort and distribution of quadrula quadrula in Manitoba

There are few historical records for Q. quadrula in Manitoba. Clarke (1973) summarized the history of malacological research in the Canadian Interior Basin as well as results from investigations into mollusc distributions from 1959-1969. During this time, surveys within Manitoba were conducted for 7 years. A total of 103 stations were examined and approximately 15,310 specimens representing 13 species were collected. Sampling methods included visual search in clear water, using a glass-bottomed viewing box, and feeling by hand. This indicates collecting was done close to shore in water that would not exceed waist deep (approximately 1 m). From 1961 to 2000 Pip (pers. comm. 2004) investigated freshwater molluscs in Manitoba and recorded the presence of freshwater mussels at a variety of sites along the Assiniboine River, tributaries of the Red River, and Lake Winnipeg. These two sources, with the contribution of a single study by Scaife and Janusz (1992), provide the bulk of information for the distribution of Q. quadrula in Manitoba up to 2000.

Results summarized by Clarke (1973) indicated that, within the Hudson Bay drainage, Q. quadrula was distributed within the Red River and lower reaches of larger tributaries of the Red River such as the Assiniboine and Roseau rivers in Manitoba (Figure 6), Red Lake River in Minnesota, and the Pembina and Sheyenne rivers in North Dakota. Within Manitoba, Clarke (1973) records Q. quadrula from the Red River at St. Jean Baptiste and Aubigny and reports additional historical records from the Red River at Fort Garry, Winnipeg, and Emerson. Quadrula quadrula was also collected from the Assiniboine River in and near Winnipeg and from the Roseau River near Tolstoi. Data recorded by Pip (pers. comm. 2004) extended the distribution to the length of the Assiniboine River from Lake of the Prairies to Winnipeg and from sites on the Shell, Rat, Morris, Seine, and LaSalle rivers and from Lake Winnipeg. With the exception of the lower Assiniboine near Winnipeg, these are sites from which Q. quadrula had not previously been observed (Clarke 1973). Watson et al. (1998) and Carney (2003a; unpubl. data) also did not record Q. quadrula from those additional sites reported by Pip. The study by Scaife and Janusz (1992) in the Assiniboine River near Winnipeg, recorded Q. quadrula well within the distribution established by both Clarke (1973) and Pip (pers. comm. 2004). Taken in concert, it seems reasonable to conclude that the historical distribution of this species was limited to the Red River and the lower reaches of its tributaries, the Assiniboine River, and Lake Winnipeg.

Investigations into the freshwater mussel fauna of Manitoba in the late 1990s and early 2000s suggested a decline in the distribution of Q. quadrula. Within the Assiniboine River drainage Watson et al. (1998) and Carney (2003a) reported Q. quadrula from the lower Assiniboine River, in the stretch below the Portage Diversion, a large water control dam located at Portage la Prairie that diverts water from the Assiniboine River north to Lake Manitoba. Watson et al. (1998) surveyed 18 sites on 157 km of the Assiniboine River between Portage la Prairie and Winnipeg and recovered Q. quadrula from four sites. Watson et al. (1998) searched an additional 167 sites on 15 rivers draining into the Assiniboine River and encountered no evidence of Q. quadrula at any of these sites. Carney (2003a, 2004a,b) surveyed 67 sites on ten rivers and recovered live Q. quadrula from some sites on the lower Assiniboine River in many of the same stretches as reported by Watson et al. (1998). In addition, Carney (2003a) collected a single, small individual approximately 50 km upstream of the Portage Diversion (Figure 7). This represented the only documented case of Q. quadrula upstream of the Portage Diversion at that time. Extensive subsequent surveys from the Portage Diversion upstream to the Shellmouth Reservoir did not encounter any other individuals of this species (Carney unpubl. data). However, Mazur (2007) as part of a mussel relocation associated with a bridge construction, reported four live Q. quadrula in the Assiniboine River at the town of Brandon. These animals were recovered using SCUBA in a transect across the river. This suggests that Q. quadrula is present in the full stretch of the Assiniboine River up to the Shellmouth Reservoir, but confirmation will require searches using SCUBA in deep water not accessible using the previous search methods (by hand in shallow water).

Surveys by Pip (pers. comm. 2004) throughout Lake Winnipeg in the 2000s found no evidence of Q. quadrula. A single live Q. quadrula was reported (Staton pers. comm. 2005) from the Bloodvein River, which drains into Lake Winnipeg, during a canoe trip. This area had never been surveyed for mussels before. This serendipitous discovery raised the possibility that Q quadrula is present in tributaries on the eastern side of Lake Winnipeg, and perhaps still exists in Lake Winnipeg itself. Further surveys in 2015 confirmed a large number of live Q. quadrula in the Bloodvein River (Watkinson pers. comm. 2015). The Bradbury River, a Lake Winnipeg tributary to the north of the Bloodvein River, had two live Q. quadrula recorded (Oliver and Lowdon 2015). A new site in the Wanipigow River (a Lake Winnipeg tributary) was also discovered in 2015 with three live animals being found (Watkinson pers. comm. 2015). Surveys of the Brokenhead River reported a total of six live Q. quadrula from three sites near its mouth at Lake Winnipeg (Morris unpubl. data). Collectively, these new discoveries suggest there may be isolated Q. quadrula subpopulations in tributaries on the east and north shores of Lake Winnipeg. These data are stored in the Lower Great Lakes Unionid Database.

Surveys by DFO (Morris unpubl. data) of Cooks Creek, a tributary of the Red River north of Winnipeg, recorded seven live Q. quadrula in 2013 and three live animals as well as fresh shells in 2014. Surveys of the LaSalle River at La Barriere Park south of Winnipeg reported a single live Q. quadrula in 2011. The presence in this site was confirmed with three and 29 live individuals recorded in 2013 and 2014, respectively (Morris unpubl. data). The Rat River was surveyed in 2013 and a single live individual recorded (Morris unpubl. data). Carney (2004a) encountered no live Q. quadrula from the same sites along the Red River investigated by Clarke (1973) although there was ample evidence of fresh-dead individuals stranded due to low water levels in 2003. In 2004, Carney and Watkins (unpubl. data) investigated sites along the Red River south of Winnipeg, including those reported by Clarke (1973), and found no live Q. quadrula. They did find half a dozen highly weathered empty valves. Surveys performed by DFO in 2013 near Highway 75 recorded no live animals but did recover 80 fresh whole shells (Morris unpubl. data). This supports the idea that there is a healthy assemblage of Q. quadrula in the Red River, but confirmation will be extremely difficult given the nature of the river.In 1992, live Q. quadrula were recovered from the Roseau River (Carney unpubl. data), but not in the surveys conducted in 2003-2004. It has not been recorded from this river since.

Populations in the Assiniboine appear to occur as assemblages of a few widely separated individuals separated by long stretches of river bottom composed of drifting sand that is completely unsuitable habitat. It is very likely that subpopulations persist in the Red River based on the historical record, river size, and presence of recently dead animals represented by fresh shells. The absence of extensive search effort in this river reflects the difficulty and danger associated with surveying this river due to its size, current, and turbidity. The presence of Q. quadrula in tributaries suggests the species is present in the Red River but this has not been confirmed due to the difficulties in sampling. The presence in Bloodvein, Bradbury, and Wanipigow rivers raises the distinct possibility of undiscovered assemblages in other rivers draining into Lake Winnipeg. It is unknown if subpopulations persist in the Roseau River. Recent investigations have not recovered evidence of this species in this river at sites where it has been reported. However, the limited amount of search effort on this river, and low mussel densities cannot preclude the presence of Q. quadrula in the Roseau River. All of these are within the historical EOO, but do increase IAO.

Habitat

Habitat requirements

Quadrula quadrula is found in a variety of habitats, including medium to large rivers with slow to moderate current, big river embayments, Great Lakes coastal wetlands and embayments, shallow lakes, and in deep river impoundments. It has been recorded from mud, sand, and gravel substrates. Preferred substrates have been reported as sand and fine gravel (Parmalee and Bogan 1998) to mud and sand (Clarke 1981). This variability likely reflects the adaptability of this species to particular habitats and a variety of substrates. In Canada, Q. quadrula is most typically recovered from medium to large rivers in firmly packed coarse gravel and sand to a substrate of firmly packed clay/mud. Quadrula quadrula is usually recovered at the surface of the substrate in the “tombstone” position with its posterior margins exposed to the water current and the anterior firmly embedded in the substrate. In both Ontario and Manitoba, it has been recorded historically from larger lakes, but data indicate it has largely been lost from open water habitats due to competition and habitat alteration by dreissenids and agricultural runoff (Schloesser and Nalepa 1994; Pip pers. comm. 2004).

Habitat trends in Ontario

The invasion of the Great Lakes by the dreissenid mussels began in 1986 (with Zebra Mussels) and resulted in the near extirpation of native mussels from Lake Erie, Lake St. Clair, and the Detroit and Niagara rivers by the mid-1990s. Only isolated communities with reduced species’ richness and relatively low abundance still survive in several bays and marshes along the U.S. shore of Lake Erie and in the delta area of Lake St. Clair. As Q. quadrula has always been rare in these waters, the loss of these habitats is less significant for this species’ overall population than for many other unionids. Interestingly, Q. quadrula is the dominant species of unionid in coastal areas of western Lake Erie (US side of the lake), representing >60% of the remnant fauna where unionids have been able to survive the dreissenid mussel invasion (Zanatta et al. 2015). Despite similar types of habitat (embayments, drowned rivermouths, and coastal wetlands) on the Canadian side of Lake Erie, Q. quadrula is only currently found in Lake Henry (a coastal embayment on Pelee Island, Cairns pers. comm. 2015), Rondeau Bay, and at the mouth of the Grand River. The habitats in coastal embayments of western Lake Ontario are very similar hydrologically to those where Q. quadrula is present in western Lake Erie (Zanatta et al. 2015). The watersheds of the Lake Ontario coastal embayments where Q. quadrula is currently found are: Twenty Mile Creek (Jordan Harbour), Sixteen Mile Creek, Fifteen Mile Creek/Pond, and Cootes Paradise (Hamilton Harbour), and all show signs of heavy nutrient loading (phosphorus) and degraded forest and riparian zone conditions (NPCA 2012).

Mussel communities in the Grand River declined dramatically from a historical total of 32 species to only 17 by the early 1970s. Kidd (1973) blamed this decline on pollution, siltation, and the presence of dams. He found few mussels living below dams or in reservoirs and noted that none of the dams had fishways. He also found that dissolved oxygen concentrations were low and turbidity was high in the lower reaches of the river, most likely due to agricultural runoff. Sewage pollution was probably the major cause of the decline of mussels in this river (Metcalfe-Smith et al. 2000b). At the time of Kidd’s surveys, only seven of the river’s 22 sewage treatment plants (STPs) had secondary treatment in place for the past 10 years, seven others had upgraded from no treatment to secondary treatment during that time, and the remaining eight were in the process of installing treatment facilities for the first time. Twenty-five years later, Metcalfe-Smith et al. (2000b) found that the mussel communities of the river had rebounded - most likely in response to significant improvements in water quality and a corresponding increase in the number of warmwater fishes from 16 to 26 species (Coleman 1991). McNichols et al. (2012) confirm that 26 mussel species can be found alive in the Grand River as of 2011, including four species listed as Endangered under the Canadian Species at Risk Act (SARA). All of the five species which appear to have been lost from the Grand River are also listed as Endangered under SARA. The human population of the watershed almost tripled from 375,000 to 985,000 between 1971 and 2014 and is expected to grow to 1.53 million by 2051 (GRCA 1997, 2014). The percentage of the minimum daily flow consisting of treated effluent from STPs ranged from 1% to 22% in 1993 and the capacity of the river to receive additional wastewater at reasonable cost is in question. The proportion of the Grand River basin in agricultural use increased from 68% in 1976 to 75% by 2014 (GRCA 2014). Row crop farming has increased, and along with it the potential for greater soil erosion and runoff of pesticides and fertilizers. Livestock production has changed, becoming more concentrated and specialized, and focusing on pigs and sheep rather than cattle. There has also been a change in manure handling from solid to liquid, and inadequate management of these liquid wastes has become a problem in some areas (GRCA 1998). The dam at Dunnville near the mouth of the Grand River has been in place since 1829 and is known to be a barrier to upstream fish movement despite the existence of a fishway (Bunt et al. 2000). Despite being a barrier to upstream fish movement and being in the middle of the area occupied by Q. quadrula in the Grand River, the Dunnville dam does not appear to have any effect on the genetic structure of Q. quadrula with no significant differentiation between upstream and downstream subpopulations (Hoffman and Zanatta unpubl. data). It is possible that the dam has not been in place long enough (given the generation time of Q. quadrula) for genetic differentiation to become evident.

Habitat trends for the Sydenham River watershed are summarized from Staton et al. (2003) and SCRCA (2013). Prior to European settlement, the Sydenham River watershed was 70% forest and 30% swamp. By 1983, 81% of the land area was in intensive agriculture (mainly corn and soybean crops), with only 12% forest and <1% swamp remaining. Sixty percent of the watershed is tile drained. Total phosphorus (TP) levels have consistently exceeded the provincial water quality objective (PWQO) over the past 30 years. SCRCA (2013) suggests phosphorus is stabilizing or improving between 2005 and 2010 in the Lower East Sydenham and Middle East Sydenham sub-watersheds where Q. quadrula is recorded. Chloride levels have been relatively low but are slowly increasing - a widespread pattern that has been attributed to the increased use of road salt. Sediment loadings from overland runoff and tile drains are high and the north branch of the river is particularly turbid. Wooded riparian zones, which are important for bank stabilization and interception of nutrients and sediments from overland runoff, are very limited. The human population of the Sydenham River watershed is small (74,000), with 50% rural and 50% living in towns and villages. Despite a modest rate of population growth, all municipalities have upgraded their sewage treatment facilities over the past 30 years. Leakage of nutrients and contaminants from rural septic systems is a significant and ongoing problem, especially in the north branch.

Habitat trends for the Thames River watershed (including Baptiste Creek) are summarized from Taylor et al. (2004), UTRCA (2012), and LTVCA (2012). Agriculture is the dominant form of land use in the Thames River watershed, with 75% of the land area in the upper Thames and 88% in the lower Thames in agricultural use. Forested areas have been reduced to 11.3% of the land area in the upper Thames and 10% in the lower Thames. Ten percent of the watershed is classified as urban, with an overall population of 515,640 concentrated in the cities of London, Stratford, and Woodstock in the upper watershed and Chatham in the lower watershed. As the land was cleared, flooding became a serious problem. Three large dams and reservoirs were constructed in the upper watershed between 1952 and 1965. Numerous private dams and weirs have been installed since the 1980s and there are now 177 structures in the upper watershed and 65 in the lower watershed. Dreissenids were discovered in Fanshawe and Springbank reservoirs in 2003 and have since spread downstream where they were found attached to native mussels in 2004 (Morris unpubl. data). Tile drainage dominates 56% of the land in the watershed. Water quality data collected since the 1960s show that concentrations of phosphorus and heavy metals are declining while nitrate and chloride levels are on the rise. The number of pollution spills has risen to 670 reported incidents in 2006 - 2010 from 380 incidents in a timespan five years earlier. The upper Thames River hosts 22 wastewater treatment facilities.

Habitat trends for the Ausable River watershed are summarized from Nelson et al. (2003) and ABCA (2013). Mussel habitat in the Ausable River has been dramatically altered over time. Prior to European settlement, 80% of the basin was covered in forest, 19% was in lowland vegetation, and 1% was marsh. By 1983, 85% of the land area was in agriculture (70% in row crops) and only 13% remained in small unconnected woodlots, similar to the current amount (14%). Over 70% of the basin is now in tile drainage and TP concentrations have increased in at least the upper Ausable River, in contrast to E. coli levels, which have dropped since 2007. The natural course of the lower portion of the river was destroyed in the late 1800s, when it was diverted in two places to alleviate flooding. The Ausable River has been described as “event responsive”, which means that there are large increases in flow during runoff events following storms. The nearby Sydenham and Thames rivers are more stable in this regard (Richards 1990). There are 21 dams in the watershed that cause sediment retention upstream and scouring downstream. Nitrate levels currently exceed federal guidelines for the prevention of eutrophication and the protection of aquatic life and are slowly rising. Mean total suspended solid concentrations in the lower Ausable River exceed levels required for good fisheries. The Bayfield River falls into the care of the Ausable Bayfield Conservation Authority and fares worse than the Ausable River in some aspects of habitat trends. The amount of forest cover is less, at 7.2% in 2012, and E. coli concentrations are more than double. In terms of pollution, TP levels are lower in the Bayfield River headwaters than the watershed average, similar to the amount of area occupied by agriculture (83%; ABCA 2013).

The Welland River watershed has been drastically altered over the last 200 years with the construction of the Welland Canal. The reach upstream of the canal (including the Oswego River and Coyle Creek) where Q. quadrula is currently found is an agricultural watershed with poor surface water quality due to very high nutrient loadings (phosphorus) and degraded forest cover and riparian zones (NPCA 2012). The lower river is largely fed by waters diverted from the Welland Canal (Lake Erie) and the reach of the river from Chippawa, Ontario to the Niagara River has had its flow reversed to enter the power plant diversion canal around Niagara Falls. There are historical records of Q. quadrula from the lower reach of the river. The water quality in the lower Welland river is poor due to high nutrient loads (phosphorus), but forest and riparian cover is considered fair (NPCA 2012).

Habitat trends in the other watersheds where Q. quadrula are known include the Ruscom River and some small streams in southern Lake Huron (Lambton County). The Ruscom River is highly degraded in terms of nutrient loading (phosphorus) and forest cover, being in nearly a completely agricultural landscape (Watershed Checkup 2015). Cow Creek and Perch Creek/Tefler Diversion Channel in Lambton County are highly degraded, deteriorating small streams in suburban Sarnia; both have poor water quality due to nutrient loading (phosphorus) and have poor to very poor forest and riparian zone conditions (SCRCA 2013).

Habitat trends in Manitoba

The Red and Assiniboine river drainages flow through what once was tall-grass to mixed-grass prairie. This is one of the most altered biomes on the planet with less than 1% remaining (Meffe and Carroll 1997). European colonization, breaking of the land with the plow, and contemporary industrial-scale agriculture have all contributed to the demise of this biome. The majority of the land within these watersheds is now agricultural, being tilled for grain and oilseed crops, being used for grazing, or urban/industrial. The growing hog industry with high density hog barns being established throughout the watershed presents a potential threat due to nutrient loading as a consequence of runoff, or catastrophic failure of sewage storage systems such as lagoons (Vandean 2003). The effect on the rivers that flow through this landscape cannot be understated. The major current concern is non-point source nutrient enrichment from agricultural runoff (Manitoba Conservation 2000). A second issue is damage to river banks resulting from uncontrolled access of cattle herds to the river. Industrial water removal and usage is also a water quality concern. The most recent issue relating to water quality in Manitoba relates to industrial hog barns. These are operations raising hundreds to thousands of hogs per site annually. The waste produced is of particular concern either due to the potential for catastrophic spills from storage tanks or from runoff after the waste has been applied to the land as a “natural fertilizer”.

The major concern for Q. quadrula habitat in Manitoba is water quality. Jones and Armstrong (2001) analyzed existing data on water quality in Manitoba and reported a significant increase in total nitrogen (TN) and TP in the Red River and Assiniboine drainage in the previous 30 years. These increases ranged from 29% to 62% for TP in the Red and Assiniboine rivers, respectively, and from 54% to 57% for TN in the Red and Assiniboine rivers, respectively. These two nutrients are major contributors to nutrient enrichment and loading of waterways that can result in cultural eutrophication and degradation of water quality. Jones and Armstrong’s (2001) study was followed by Bourne et al. (2002) who focused on the Red and Assiniboine watersheds. The data were reported as TN and TP expressed as tonnes per year due to extreme variation in nutrient loads at weekly, seasonal, and yearly time scales. Bourne et al. (2002) found that nutrient enrichment was substantial and primarily resulted from non-point sources, in particular agricultural runoff; they reported that from 1994-2001 the Assiniboine River on average carried 3,682 tonnes per year of TN and 637 tonnes per year of TP near its outflow into the Red River. During this same time period, the Red River on average carried 15,301 tonnes per year TN and 4,269 tonnes per year TP. The result of this nutrient input has been the increasing eutrophication of Lake Winnipeg such that basin-wide algae blooms are visible from space (Lake Winnipeg Implementation Committee 2005). These nutrient inputs and high loads are not limited to the Red and Assiniboine. Graveline et al. (2005) report similar situations for the Rat River and Joubert Creek. Corriveau et al. (2013) reported that phosphorus and nitrogen inputs into the watershed are most strongly affected by spring runoff and snowmelt.

There is an accumulating body of evidence that freshwater mussels are sensitive to ammonia at levels below what is acceptable by the U.S. Environmental Protection Agency (U.S.E.P.A. 2013) (Augspurger et al. 2003; Bartsch et al. 2003; Mummert et al. 2003). The juvenile stage appears most vulnerable to this exposure, which can result in adult populations persisting, but no recruitment. This could lead to the illusion of a healthy population based on the persistence of adult populations. None of the aforementioned studies specifically tested Q. quadrula, or any members of that genus. However, tests revealed juvenile sensitivity to low ammonia concentrations across a variety of species (Augspurger et al. 2003) that may be extended to Q. quadrula. The increasing trajectory of nitrogen loading in Manitoba streams coupled with the apparent absence of recruitment into some of the existing Q. quadrula populations (see Manitoba, Abundance and Fluctuations and Trends) is therefore of concern.

Biology

Life cycle and reproduction

Freshwater mussels in the family Unionidae have a complex life cycle that includes a larval stage called a glochidium (pl. glochidia) that is an obligate parasite, most commonly on a fish host. The life history of Q. quadrula reflects the general pattern of unionid mussels. During the spawning period, the male releases sperm into the water through the excurrent siphon. Sperm are carried by the water current, taken in by the female through the incurrent siphon, and gills filter the sperm out of the water. In the female, ova are released and held in a specialized area of the gill called the marsupium (pl. marsupia). The sperm that has been filtered from the water is carried into the marsupium where the ova are fertilized. Fertilized ova develop into glochidia and are brooded in the marsupium.

Quadrula quadrula is dioecious. Males and females cannot be distinguished based on external morphology. Females are considered to be a short-term brooders (tachytictic). Reports on the length of the brooding season appear to vary with the locality ranging from May to August in the U.S. (Parmalee and Bogan 1998) and late spring to early summer in Canada (Clarke 1981) and may be temperature dependent. In the Sydenham River, gravid Q. quadrula have been found between mid-July and mid-August (Morris unpubl. data). In Manitoba, Q. quadrula brooding glochidia have not been observed, and ova have never been observed in the marsupium later than mid-June (Carney 2003a, pers. obs.). This would seem to suggest that at least in Manitoba, there may not be successful reproduction every year and that there is a very limited time during which glochidia are available for host infestation.

Quadrula quadrula glochidia are ovate, lack hooks, and measure approximately 80 μm in length and height (Clarke 1981; Morris unpubl. data). Quadrula quadrula releases glochidia in lanceolate conglutinates that are approximately 10 mm in length and 3 mm in width at the broad end. The conglutinate (a solid aggregation of glochidia) is typically white and may have sparse randomly distributed dark “dots”. Presumably the fish host is infested when it bites the conglutinate releasing the glochidia, which can then attach to the gills. While not directly observed in Q. quadrula, other closely related members of the genus Quadrula have been observed using a mantle lure that is hypothesized to assist in attracting their catfish hosts (Seitman et al. 2012). There are no data on the fecundity of Q. quadrula. Haag and Staton (2003) investigated reproductive traits of several mussel species including the congeners Q. asperata and Q. pustulosa collected from sites in Mississippi and Alabama. For those two species, they report that fecundity increases with shell length. There were differences in maximum fecundity, and fecundity as a function of age, for these two species. Quadrula asperata had a maximum fecundity approaching 30,000 developing ova in the gills whereas Q. pustulosa had a maximum fecundity of approximately 50,000 ova. Haag and Staton (2003) also report differences in age at which reproductive capacity is maximized for these two species. Maximum fecundity for Q. asperata is reached around 15 years of age while Q. pustulosa reaches maximum fecundity around 30 years of age (Haag and Staton 2003). Fecundity for both species declines following those maxima. Quadrula quadrula likely reaches sexual maturity around the same age as Q. asperata and Q. pustulosa, somewhere between three and ten years. The differences reported for these two congeners make it difficult to predict maximum fecundity and age after which fecundity declines for Q. quadrula. It seems likely that cooler summers and longer, colder winters in Canada could extend time to maturity and would result in fecundity values that are much less than those reported for Q. asperata and Q. pustulosa from individuals collected from the southern U.S.

Howard and Anson (1922) identified the Flathead Catfish (Pylodictus olivaris) as a suitable host. The Flathead Catfish is not considered to be native to Canada (Scott and Crossman 1973) although four specimens have been caught in Canadian waters of Lake Erie (Crossman and Leach 1979; Gagnon pers. comm. 2005). There are no documented specimens of this species recorded from Manitoba. The Flathead Catfish was the only known host for Q. quadrula until Schwebach et al. (2002) reported successful transformation of Q. quadrula glochidia on Channel Catfish (Ictalurus punctatus), a species common in both Manitoba and Ontario (Scott and Crossman 1973; Stewart and Watkinson 2004). The time required for successful metamorphosis was 51-68 days with water temperature starting at 13°C and ending at 20°C (Schwebach et al. 2002). It seems reasonable to assume that Channel Catfish would serve as a suitable host for Canadian Q. quadrula populations. Other Quadrula species have also been recorded as having catfish species as suitable hosts (Fuller 1974). It is worth noting that the Brown Bullhead (Ameiurus nebulosus) has a range that is closest, and almost identical, to that of Q. quadrula (Lee et al. 1980) and it seems likely that this catfish species would be a suitable host, although this has yet to be demonstrated.

Quadrula quadrula is a long-lived species. Carney (2003a,b, pers. obs.) using shell thin sections (Clark 1980; Neves and Moyer 1988) reported individuals from the Assiniboine River in Manitoba up to 64 years old with an average age of 22.1 years (n = 47). Age data specific to Ontario populations are not available but are likely to be consistent with those reported from Manitoba. Therefore the average generation time is estimated to be 20 years.

Physiology and adaptability

No studies specific to the physiology of Q. quadrula are known. As molluscs, they would require a supply of calcium sufficient for shell growth during their lifetime. Juveniles of other unionid species are known to be sensitive to ammonia at levels below current U.S.E.P.A. water quality criteria and it seems likely this sensitivity would extend to Q. quadrula (see Habitat Trends in Manitoba). Quadrula quadrula must be able to survive a wide range of temperatures. In winter the rivers in Manitoba would be ice covered with water temperature at or near 0ºC while in summer water temperatures can reach 27ºC.

The range of suitable habitats suggests this species is quite adaptable. Glochidia have been successfully transformed in an experimental situation using Channel Catfish as host. Informal accounts of these mussels being successfully transplanted by commercial interests suggest this species can be transported and transplanted.

Dispersal and migration

Adult freshwater mussels are largely sessile, typically moving no further than 100 m, and usually much less than that. Therefore the ability of the adult stage to disperse or migrate is highly constrained, although still possible (Schwalb and Pusch 2007). The known hosts of Q. quadrula are catfish species that can travel great distances over short time periods (Wendel and Kelsch 1999; Stewart and Watkinson 2004; Butler and Wahl 2011). This would suggest that Q. quadrula is capable of being dispersed over large distances. Berg et al. (1998) used allozyme variation to show there were high levels of gene flow among distant populations of Q. quadrula within the Ohio and Mississippi drainages. Populations in Ontario and Manitoba each lie within drainages that are isolated from each other and have been separated from the Ohio-Mississippi drainages for thousands of years so dispersal between these watersheds is not possible (see Rescue Effect for dispersal within drainages connected with the U.S for each DU).

Interspecific interactions

For information on host fish usage, see Life Cycle and Reproduction.

Predators of mussels include fishes, mammals, and birds. Baker (1918) identified Freshwater Drum (Aplodinotus grunniens), Lake Sturgeon (Ascipenser fulvescens), Pumpkinseed (Lepomis gibbosus), Round Goby (Neogobius melanostomus), and suckers (Catostomus spp.) as fish predators of mussels. Muskrat (Ondatra zibethicus) predation can be an important factor that may limit some mussel populations (Tyrrell and Hornbach 1998) and muskrats have been reported to prey upon Q. quadrula (Nakato et al. 2005). Muskrats have been reported to eat as many as 37,000 mussels annually in a northern Alberta lake (Convey et al. 1989; Hanson et al. 1989) and may represent a serious threat to endangered species and populations (Neves and Odum 1989). Larval chironomids feeding on mussel tissue can result in the loss of up to 50% of the gill (Gordon et al. 1978), affecting both respiration and reproduction, and may represent either parasitism or predation depending on definitions used.

Mussels are parasitized by helminths (Digenea) and mites which may have a detrimental effect on the infected mussel. Mussels can be infected by both adult digeneans and by larval digeneans that include the sporocyst or metacercaria stages. Parasitism by sporocysts can result in sterilization of the infected mussel (Esch and Fernandez 1993). An extensive survey of mussels in Manitoba that included examination for parasites did not show parasitism of Q. quadrula by sporocysts (Carney 2003a). A single individual Q. quadrula was infected with metacercariae but this stage has not been demonstrated to cause sterility and there was no indication of sterility in that infected individual. A variety of adult helminths also can parasitize mussels. Aspidogaster conchicola in the pericardial sac and kidney and Cotylogaster occidentalis in the gut have both been reported from Q. quadrula (Hendrix et al. 1985). Carney (2003a) examined Q. quadrula from the Assiniboine River in Manitoba and reported approximately 60% infected with A. conchicola and 6% infected with C. occidentalis. Mean intensity of infection ranged from 1-71 (mean = 17) and 1-2 for A. conchicola and C. occidentalis, respectively. Infection by A. conchicola may cause damage to the renal epithelium (Williams 1942; Michelson 1970).

Adult mites belonging to the family Unionicolidae are common symbionts in the mantle cavity of mussels and also in the mantle tissue as parasitic larvae, and there may be close evolutionary ties between the two groups that possibly represent examples of coevolution, in some cases (Vidrine 1996). Carney (2003a) reported no Q. quadrula collected from the Assiniboine River in Manitoba to be infested with mites.

To date there are no data pertaining to parasitism of Q. quadrula from Ontario. It does seem likely that what has been reported from Manitoba would also be valid for populations in Ontario, given that the hosts and parasites are present in both regions (Hendrix et al. 1985; Carney 2003a).

There has been extensive debate regarding the food and source of nutrition of unionid mussels. Much of this debate has centred on the fact that there are problems in separating what is ingested and what is actually assimilated. As unionids filter water, they feed by sorting food particles in the mantle cavity before ingestion and in the stomach after ingestion (Nichols and Garling 2000). Although the feeding and nutrition of Q. quadrula has not been specifically addressed, Raikow and Hamilton (2001) and Christian and Smith (2004) indicate that a variety of mussel species were using similar food resources. The following discussion assumes that what has been reported for other mussel species can be extended to Q. quadrula.

Available information indicates adult mussels feed upon fine particulate organic matter suspended in the water column (Tanklersley 1996; Ward 1996). However, it is unclear which components of this suspended material are actually used for nutrition (Gatenby et al. 1993; Nicholls and Garling 2000). Allen (1914) reported diatoms and algae in the gut of unionids and proposed that algae, protozoa, bacteria, and organic material were the primary sources of nutrition (Allen 1921). Some ingested materials are not necessarily digested but may survive passage through the digestive tract (Churchill and Lewis 1924; Miura and Yamashiro 1990). Imlay and Paige (1972) suggested that unionids derive their nutrition from feeding on bacteria and protozoa. Nichols and Garling (2000) studied the diet of seven mussel species using stable isotope analysis, gut contents, and biochemical analyses and determined there was positive selection of food items in the diet based on the concentration of algae and diatoms in the gut. Although algae and diatoms were selectively ingested and concentrated in the gut, the main source of nutrition was bacteria. However, algae were still a necessary part of the diet by providing essential nutrients (Nichols and Garling 2000).

There is also uncertainty regarding the degree to which mussels feed upon detritus and organic matter within the substrate. Juvenile mussels may use cilia on their foot to feed from the substrate, a method called pedal feeding. Gatenby et al. (1993) suggested juveniles fed on algae and silt. Yeager et al. (1993) and Yeager and Cherry (1994) have shown that juvenile mussels may feed primarily on bacteria from within the substrate but the importance of this as a source of nutrition for adults is less clear. Adult mussels are capable of filtering suspended particles ranging in size from 0.9 - 250 µm (Silverman et al. 1997) suggesting suspended organic materials are important in the diet and nutrition of mussels. However, Raikow and Hamilton (2001) used stable isotope ratios to determine diets of 12 mussel species and suggested their diet was composed of 80% deposited material and 20% suspended material.

If the preceding data apply to Q. quadrula the following conclusions regarding feeding may be drawn. Feeding on interstitial material may be the primary source of nutrition for juveniles. Adults may also be feeding from the substrate as well as upon organic materials suspended in the water column. Bacteria appear to be the primary source of nutrition with algae supplying many essential elements in the diet. Clearly there is much more research required to clarify the food habits and nutrition of unionid mussels.

Population sizes and trends

Ontario

Sampling effort and methods

Historical surveys

Approximately 80% of the information on the historical distribution of Q. quadrula in Ontario is based on either museum specimens or presence-absence data. There is little if any information on sampling method, search effort, numbers of sites visited where the species did not occur, or even whether the animals were dead or alive when collected. Data on relative abundance (Catch-Per-Unit-Effort or CPUE) are available from timed-search surveys of ten sites on the Sydenham River in 1985 (Mackie and Topping 1988) and 16 sites on the same river in 1991 (Clarke 1992). Two of the sites surveyed by Mackie in 1985 were re-surveyed 12-13 years later by Metcalfe-Smith et al. (1998b, 1999), so these data can be compared. Three of the sites surveyed by Clarke in 1991 were also re-surveyed in 1997-98, but Q. quadrula was never found at any of these sites. Kidd (1973) surveyed 68 sites on the Grand River in 1970-72 and 14 of these sites were re-surveyed 25 years later using a similar sampling effort (Metcalfe-Smith et al. 2000a). Nine sites were in the upper and middle reaches of the river, which is outside the species’ distribution in the system, but five sites were in the lower reaches and can be compared.

Modern surveys

Surveys conducted between 1995 and 2015 within the range of Q. quadrula in Ontario have been either semi-quantitative (timed-searches) or quantitative (quadrat surveys). The same sampling methods and efforts were used throughout and are described below. The only exception was the 1995 survey on the Grand River, which used a lower sampling effort than other surveys (see Metcalfe-Smith et al. 2000a).

Timed-search surveys:

In rivers, surveys were conducted using an intensive timed-search technique developed by Metcalfe-Smith et al. (2000a). Briefly, the riverbed is visually searched by a team of three or more persons using waders, polarized sunglasses, and underwater viewers for a total of 4.5 person-hours (p-h) of sampling effort. Where visibility is poor, searching is done by feel. The length of reach searched varies depending on river width, but is generally 100-300 m. Live mussels are held in the water in mesh diver’s bags until the end of the search period when they are identified to species, counted, measured (shell length), sexed (if sexually dimorphic), and returned to the riverbed. Over the past 20 years, such surveys have been conducted in the Grand, Thames, Sydenham, Ausable, Maitland, Welland, Bayfield, Saugeen, Moira, Trent, and Salmon rivers and several smaller tributaries to Lake Ontario, Lake Erie, and Lake Huron by several different researchers. Between 2011 and 2015, the Ontario MNRF has surveyed 40 Lake Ontario coastal wetlands and embayments using visual/tactile and clam rake searches (12 hours each; Reid et al. 2014).

In Lake St. Clair, searches at waters depths greater than 2 m were conducted by two SCUBA divers for a total effort of 0.5 p-h whereas searches at depths less than 2 m were conducted by three people using mask and snorkel for a total of 0.75 p-h (Zanatta et al. 2002). At sites where live mussels were found (all were shallow), snorkel searches were extended to a total of 1.5 p-h. Additional intensive surveys were conducted by McGoldrick et al. (2009), Morris (unpubl. data), and Zanatta et al. (2015) in 2011 with similar amounts of effort to what was used by Zanatta et al. (2002).

Quantitative surveys:

Surveys in rivers employed an intensive quantitative sampling technique that would allow the generation of precise estimates of demographic variables such as density, size class frequencies, and recruitment levels. Strayer and Smith (2003) is the standard guide for monitoring freshwater mussels. The quantitative sampling technique employed in wadeable Ontario rivers is summarized below:

Sampling employed a 2-person search team and a data recorder and required approximately two days of work per site. At each site, roughly 400 m2 of the most productive portion of the reach (usually a riffle) was selected for sampling; because the most productive portions are chosen, caution should be used when extrapolating to estimate subpopulation sizes for entire watersheds. Quantitative sampling was conducted using 1 m2 quadrats and a systematic sampling design with three random starts. The area to be sampled was divided into blocks of equal size (5 m long × 3 m wide) and each block was further divided into 15 - 1 m2 quadrats. The same three randomly chosen quadrats were sampled in each block; thus, 20% of the 400 m2 area was sampled at each site. Each quadrat was searched by two people until all live mussels had been recovered (~ 8 person-minutes). All embedded stones (except large boulders) were removed and the substrate was excavated to a depth of 10-15 cm in order to obtain juveniles (young mussels are known to burrow deeply in the substrate for the first three years of life). All live mussels found in each quadrat were identified, counted, measured, sexed where possible, and returned to the riverbed. Several habitat variables (e.g., depth, current velocity, substrate composition) were also measured. Quantitative surveys have been conducted on the Sydenham, Thames, and Ausable rivers and portions of the Grand River (Bouvier and Morris 2010). Note that the habitat for Q. quadrula in the lower Grand River is not especially suitable for this type of survey.

A different type of quantitative survey was conducted in the delta area of Lake St. Clair. At each site, sampling was performed by several (usually three) 2-person teams, with each team consisting of a snorkeler and a helper to carry the gear and mussels. Each snorkeler swam until a mussel was seen, then surveyed a 65 m2 circular area around the mussel and collected any other live mussels found. Each team surveyed ten such circle plots. All live mussels were identified, counted, measured, sexed, and returned to the lake bottom. Methods are described in detail in Metcalfe-Smith et al. (2004) and McGoldrick et al. (2009). Such surveys were conducted in 2001 and 2003 and to a limited extent in 2004 and 2011 (Morris unpubl. data).

A new semi-quantitative approach for surveying coastal areas of the Great Lakes has been used in recent surveys (Minke-Martin et al. 2015; Zanatta et al. 2015). This method uses a 2 p-h timed search in a 0.5 ha area. This method was used in 2011 surveys of the St. Clair Delta and in the 2014 surveys of the lower Grand River (below Dunnville dam) and coastal embayments in western Lake Ontario.

Abundance

Quadrula quadrula no longer occurs in the open (deep offshore) waters of the Great Lakes and connecting channels, so there are no abundance data to discuss for these waters (see Fluctuations and Trends). Quadrula quadrula appears to be functionally extirpated from Lake St. Clair (only one individual found in last 15 years despite extensive surveys). A new record from Pelee Island suggests that it is not completely gone from the Canadian side of western Lake Erie (Cairns pers. comm. 2015) as do the fresh shells from Rondeau Bay (Reid et al. 2016). New discoveries in coastal embayments in western Lake Ontario suggest fairly large population sizes (>150 live animals collected since 2010), but no density information is currently available and the area of occupancy in these coastal embayments is fairly small (Minke-Martin et al. 2015; Morris unpubl. data). Catch-per-unit effort estimates for Jordan Habour (3.4/p-h) suggest a relatively high density in comparison to the large subpopulation sizes in the Grand, Thames, and Sydenham rivers; however, the area of occupancy of these coastal areas is relatively small.

In lotic systems, the species presently occurs in the Grand River (Lake Erie drainage), the Welland River watershed (Niagara River drainage), in the Lake St. Clair drainage in the Thames River watershed (including McGregor Creek and Baptiste Creek), the Sydenham River (including the North Branch/Bear Creek) and Ruscom River, the Ausable River (southern Lake Huron drainage), and some other southern Lake Huron tributaries of southwestern Ontario. The vast majority (estimate >75% of the total population) of Q. quadrula in Ontario appear to be in the Thames, Sydenham, and Grand rivers. Timed-search surveys were conducted at 113 sites on these rivers between 1997 and 2004 using 4.5 p-h sampling effort/site. Results of such semi-quantitative surveys can be used to compare the relative abundance of Q. quadrula populations among rivers (Table 3). Quadrula quadrula appears to be abundant at only three of the sites surveyed in the Welland River watershed, but where present in the Welland, CPUE is similar (4.6 p-h) to the rivers where Q. quadrula is found at high density in southwestern Ontario (Bouvier and Morris 2010; DFO unpubl. data). The population in the Ausable River appears to be small, with only 18 live specimens found. If CPUE is compared using only those data from sites in the occupied reaches of each river, population density is greatest in the Grand River (CPUE = 6.9 specimens/p-h), followed by the Thames (2.9), Sydenham (2.0), and Ausable (1.0). However, DFO personnel completed timed-search (4.5 p-h) surveys at each of ten sites on the lower Thames River in 2005 and found 3134 living specimens and 20 species, of which 422 were Q. quadrula (Table 3). The species was the second to third most abundant at virtually all sites (Morris and Edwards 2007). The CPUE for this species in the survey was 9.6 specimens/p-h, which is over three times the CPUE reported in previous surveys (2.9 specimens/p-h). It appears that the Thames River may have the largest population of Q. quadrula in southwestern Ontario.

Table 3. Relative abundance of Quadrula quadrula from four southwestern Ontario rivers.
River# sites surveyed# live mussels collected (all species)Frequency of occurrence of Q. quadrula (% of sites)Relative abundance of
Q. quadrula (% of community)
Catch-per-unit-effort for Q. quadrula (#/person-hour)Year(s) of surveys
Ausable25501316%0.4%0.2/p-h1998b, 2002c, 2004c
Sydenham18235750%3%1.0/p-h1997-98a,b, 2003c
Thames41
10
4906
3134
17%
100%
2%
13.5%
0.5/p-h
9.6/p-h
1997-98a,b, 2004-2005d
Grand29
5
1903
74
17%
80%
8%
55%
1.1/p-h
4.1/p-h
1997-98a, b 2004c
2011e

a Metcalfe-Smith et al. (1998b);

b Metcalfe-Smith et al. (1999);

c Metcalfe-Smith et al. (unpubl. data);

d Morris and Edwards (2007).

e Minke-Martin et al. (2015)

Catch-per-unit effort data obtained from timed-search surveys provide information on relative population density. True density estimates are only available for the Ausable, Grand, Sydenham, and Thames rivers. Table 4 presents density estimates for these rivers and extrapolates population sizes based on these densities and the biological area of occupancy (average stream width x reach length occupied) - but see caution in Ontario - Modern Surveys. The Thames and Sydenham rivers likely have populations over one million animals, while the Ausable is at least an order of magnitude smaller in population size. The Grand River only had a single site surveyed using quadrats where Q. quadrula was present (and the populations were qualitatively estimated to be more dense further downstream), thus the population size is likely underestimated (Bouvier and Morris 2010; Morris unpubl. data).

Shell length was measured for every live mussel collected during the above-described surveys. Size frequency distributions for live Q. quadrula collected during recent timed-search surveys on the Grand, Ausable, Sydenham, Thames, Welland, and Ruscom rivers are presented in Figures 8-13. Where possible, comparisons were made in size class distributions between data collected prior to the original status report and data collected since (e.g., after 2006). The data clearly show recent recruitment in all of these rivers. The only exception to this pattern of recent recruitment was in Jordan Harbour on Lake Ontario, which showed a size distribution skewed towards an older population, with little evidence of recent recruitment (Figure 14); however, excavations of the substrate were not done in Jordan Harbour.

Table 4. Current population estimates for the Great Lakes - Upper St. Lawrence population of Quadrula quadrula for sites with density estimates using quadrat methods. Note: f indicates that density estimates are only available from a single site and therefore Standard Error (SE) is not available. Modified from Bouvier and Morris (2010) and from Morris (unpubl. data) from the Sydenham River.
PopulationAverage total
unionid
density
(#/m2) (SE)
Q. quadrula
density
(#/m2) (SE)
Area of
occupancy
(m2)
Estimated
population
size
Ausable River2.065 (±1.945)0.135 (±0.121)712,637~9977 - 183,005
Grand Riverf2.253f0.030f10,827,716~324,831
Sydenham River15.826 (±1.587)0.370 (±0.092)5,800,645~1,612,579 - 2,679,898
Thames River5.045 (±0.748)0.508 (±0.187)11,733,405~3,765,144 - 8,144,262

f Morris unpubl. data

Figure 8. Size class distribution for live Quadrula quadrula collected from the Grand River (A) in 1997 (n = 97) and (B) since 2008 (n = 131). Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size class distribution for live Quadrula quadrula
Photo: © Morris unpubl. data
Long description for Figure 8

Two chart panels illustrating size class distribution for live Mapleleaf collected from the Grand River, Ontario, in 1997 (panel A) and since 2008 (panel b).

Figure 9. Size class distribution for live Quadrula quadrula collected from the Ausable River from 2002 to 2013 (n = 30). Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size class distribution for live Quadrula quadrula collected from the Ausable River from 2002 to 2013
Photo: © Morris unpubl. data
Long description for Figure 9

Chart illustrating size class distribution for live Mapleleaf collected from the Ausable River, Ontario, from 2002 to 2013.

Figure 10. Size class distribution for live Quadrula quadrula collected from the Sydenham River (A) in 1997 and 1998 (n = 62) and (B) from 2008 to 2011 (n = 112). Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size class distribution for live Quadrula quadrula collected from the Sydenham River
Photo: © Morris unpubl. data
Long description for Figure 10

Two chart panels illustrating size class distribution for live Mapleleaf collected from the Sydenham River, Ontario, in 1997 and 1998 (panel A) and from 2008 to 2011 (panel B).

Figure 11. Size class distribution for live Quadrula quadrula collected from the Thames River (A) in 1997 and 1998 (n = 68) and (B) from 2005 to 2008 (n = 318). Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size class distribution for live Quadrula quadrula collected from the Thames River
Photo: © Morris unpubl. data
Long description for Figure 11

Two chart panels illustrating size class distribution for live Mapleleaf collected from the Thames River, Ontario, in 1997 and 1998 (panel A) and from 2005 to 2008 (panel B).

Figure 12. Size frequency distribution for live Quadrula quadrula (n = 58) collected during timed-search surveys in the Welland River, Ontario in 2014. Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size frequency distribution for live Quadrula quadrula (n = 58) collected during timed-search surveys in the Welland River
Photo: © data collected for this report
Long description for Figure 12

Chart illustrating size frequency distribution for live Mapleleaf collected during timed-search surveys in the Ruscom River, Ontario, in 2010.

Figure 13. Size frequency distribution for live Quadrula quadrula (n=26) collected during timed-search surveys in the Ruscom River, Ontario in 2010. Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size frequency distribution for live Quadrula quadrula (n=26) collected during timed-search surveys in the Ruscom River
Photo: © Morris unpubl. data
Long description for Figure 13

Chart illustrating size frequency distribution for live Mapleleaf collected during timed-search surveys in Jordan Harbour, Ontario, in 2014.

Figure 14. Size frequency distribution for live Quadrula quadrula (n = 50) collected during timed-search surveys in Jordan Harbour, Ontario in 2014. Specimens <50 mm are considered juveniles and indicative of recent recruitment. Data may be biased towards larger animals as only timed search surveys were conducted (without excavations of the substrate).
Size frequency distribution for live Quadrula quadrula (n = 50) collected during timed-search surveys in Jordan Harbour
Photo: © data collected for this report
Long description for Figure 14

Chart illustrating size frequency distribution for live Mapleleaf collected during timed-search surveys in Jordan Harbour, Ontario, in 2014.

Fluctuations and trends

Quadrula quadrula appears to be extirpated from open waters of the Canadian side of Lake Erie (with the exception of the newly discovered animals in Lake Henry on Point Pelee and fresh shells at Rondeau Bay), Lake St. Clair (one live animal in 2005, none in surveys in 2011-2012), and the Detroit and Niagara rivers due to impacts of the Zebra and Quagga mussels; however, it was always extremely rare in these waters. For example, there are some scattered records from Canadian waters of Lake Erie, but only for shells. These records include four from Rondeau Bay (1894, 1961, one with no date, and 2015), five from Pelee Island (1962, 1978, 1992, 2004, and 2015) and one from Port Maitland at the mouth of the Grand River in 1936. Quadrula quadrula was found at only one of 29 sites surveyed in the offshore waters of Lake St. Clair in 1986 prior to the Zebra Mussel invasion and represented 0.7% of the 281 mussels collected from all sites (Nalepa et al. 1996). Similarly, only one of 1279 live mussels (0.08%) collected from 13 sites throughout the Detroit River in 1982-83 was Q. quadrula (Schloesser et al. 1998). Zanatta et al. (2002) collected 2356 live mussels from 95 sites in the nearshore waters of Lake St. Clair between 1999 and 2001, and only one mussel (0.04%) was a Q. quadrula (collected in 1999 at the mouth of the Thames River). Nevertheless, even at low population densities, because of their enormous size these waterbodies must have once supported a substantial proportion of the Ontario population of this species but it has not been found in the lake despite continued work through the 2000s (McGoldrick et al. 2009) and 2011 (Morris unpubl. data). In Lake Erie, except for fresh shells at Rondeau Bay and recent findings of live animals in Lake Henry on Pelee Island, Q. quadrula has not been observed on the Canadian side of Lake Erie since the establishment of dreissenid mussels. Quadrula quadrula in the coastal embayments of western Lake Ontario was unknown prior to 2010, thus there are no data on trends. Despite heavy dreissenid mussel presence in Lake Ontario, the Q. quadrula in the coastal embayments remain and are relatively free of heavy dreissenid mussel infestation. These coastal habitats appear to be similar to those on the U.S. side of western Lake Erie (Zanatta et al. 2015).

Catch-per-unit-effort for Q. quadrula in the Sydenham River was 1.4/p-h over ten sites in 1985 (Mackie and Topping 1988), 0.12/p-h over six sites in 1991 (Clarke 1992), and 1.1/p-h over 18 sites in 1997-98 and 2003 (Metcalfe-Smith et al. 1998b; Metcalfe-Smith and Zanatta 2003). Two sites were surveyed in both 1985 and 1998; CPUE for a site on the East Sydenham was 8.0/p-h in 1985 and 1.1/p-h in 1998, and CPUE for a site on Bear Creek was 5.0/p-h in 1985 and 1.3/p-h in 1998 and was anecdotally still abundant in 2010 (Morris unpubl. data). These data suggest that Q. quadrula may have been declining in abundance in the system but this is inconsistent with evidence showing that the species is encountered more frequently now than in the past (see Search Effort and Distribution of Quadrula quadrula in Ontario).

Kidd (1973) collected 0, 0, 0, 1, and 9 Q. quadrula from five sites on the lower Grand River in 1971-72 whereas Metcalfe-Smith et al. (2000a) collected 0, 0, 1, 57, and 27 specimens from the same sites 25 years later. Kidd (1973) found that the number of mussel species living in the river had declined dramatically from historical counts - only six of 25 species previously reported from the lower reaches were still present in the 1970s. This decline was attributed to siltation, the creation of dams and reservoirs, and especially sewage pollution. Quadrula quadrula was one of the species that had survived. Populations of most mussel species, including Q. quadrula, have since rebounded due to significant improvements in water quality.

There are no data available for determining if there have been changes in population size over time for Q. quadrula in the Ausable or Thames rivers, although the recent data on 10 sites in the lower Thames suggests a healthy population (Figure 11).

Overall, the population size appears stable in the Great Lakes - Upper St. Lawrence (or Ontario) DU. The large majority of the population for this DU appears to reside in three rivers: the Thames, Sydenham, and lower Grand with millions of animals estimated. Density estimates made over the last 15 years and recent size class data indicate that these are all apparently stable and relatively healthy; however, the longevity of this mussel could also mask abundance trends. Less can be elucidated about subpopulation sizes or trends in most of the other currently occupied waterbodies, but several of these may also be quite large and apparently stable (e.g., the Welland River watershed, and coastal wetlands and embayments in western Lake Ontario) with evidence of recent recruitment.

Rescue effect

While Ontario subpopulations of Q. quadrula are isolated from one another and from subpopulations in the U.S., there is a possibility of rescue. Even though subpopulations in tributaries to the lower Great Lakes on both sides of the Canada/U.S. border may once have been connected by those in Lake Erie and Lake St. Clair, native mussels have been virtually extirpated from the lakes due to impacts of Zebra and Quagga mussels, making connections difficult. But, given that the catfish hosts are highly vagile (Wendel and Kelsch 1999; Butler and Wahl 2011) and that there are several large subpopulations (e.g., coastal areas of western Lake Erie, Maumee River, Belle River, Saginaw River) remaining on the U.S. side of Lake Erie (Zanatta et al. 2015) and Lake Huron (Zanatta unpubl. data), rescue could potentially occur although intervening areas may be unsuitable for both mussel and host. Recent genetic work (Paterson et al. 2015; Hoffman and Zanatta unpubl. data; Mathias and Zanatta unpubl. data) has shown a high degree of recent gene flow (Nm>1, see: Population Spatial Structure and Variability) between US and Canadian populations although there also was evidence of limited gene flow between subpopulations in coastal areas of western Lake Erie, the lower Grand River, the Welland River, and embayments in western Lake Ontario.

Manitoba

Sampling effort and methods

Historical surveys

All the historical information for the distribution of Q. quadrula in Manitoba consists of either museum specimens or presence-absence data (e.g., Clarke 1973). Data on sampling methods and search efforts are unavailable. Sites where Q. quadrula did not occur can be determined by comparison with sites from which other species were recovered. However, there are no data on sites that were examined from which no mussel species were recovered.

Modern surveys

Recent surveys in Manitoba can be divided into two time periods. There are those that occurred from the early 1990s to about 2005, and those that occurred after 2011, with a single mussel relocation effort in Brandon in 2007. The goals of these surveys differed, as did the collecting methods and efforts. This makes comparisons difficult.

In 1992, under the direction of Dr. Terry Dick from the University of Manitoba, Carney and colleagues (unpubl. data) surveyed four sites on the Assiniboine River and one site on the Roseau River to provide a preliminary determination of which mussel species were present. Quadrula quadrula was recovered from three sites on the Assiniboine and from the single site on the Roseau River. This undertaking is best considered as qualitative because of different times spent searching involving different numbers of people (range from 1-5). Search in all cases was by feel. The effort expended varied from a low of 2 p-h to a high of 10 p-h (Table 5).

Table 5. Relative abundance of Quadrula quadrula from the Assiniboine River in Manitoba from surveys based on timed searches.
Source# sites surveyed# live mussels collected (all species)Frequency of occurrence of Q. quadrula
(% of sites)
Relative abundance of Q. quadrula (% of community)Catch-per-unit-effort for Q. quadrula (#/person-hour)
Carney 1992 unpubl.3540100%11%1.26
Watson et al. 1998187527%8%0.66
Pip 2000302n/a0.006%n/an/a
Carney 2003a (below Portage Diversion)623933%18%1.5
Carney 2003a (above Portage Diversion)163166%0.3%0.025
Watkins 2003 unpub.648533%6.19%1.54
Watkins and Carney 2004 unpubl. g1n/a100%n/a2

g This survey was targeted to Quadrula quadrula and no other species were recorded. Numerous individuals of several species were recovered.

Scaife and Janusz (1992) investigated the viability of a commercial shell harvest from the lower Assiniboine River. They reported the results of a survey over 21 km using randomly placed 1 m2 quadrats and SCUBA, found 62 Q. quadrula from 24 of 120 quadrats, and an average density of 0.52/m2.

Watson et al. (1998) undertook a study to determine the distribution and abundance of freshwater mussels in the lower Assiniboine River and 15 of its tributaries. Sampling sites on the Assiniboine between Portage la Prairie and Winnipeg were selected following a stratified sampling design (Watson et al. 1998). Eighteen transects across the river were sampled using a mini bullrake. Collecting involved raking the bullrake across the substrate five times at each of five equidistant points across the river. Tributaries were sampled by sight, by feel, or by using the bullrake, depending on water clarity and depth. Thirty person-minutes were spent searching at each site. They (Watson et al. 1998) recovered a total of six live Q. quadrula from five of the 17 sites surveyed on the Assiniboine River, with empty valves recorded at one additional site. There was no evidence of Q. quadrula from any of the 167 sites surveyed in tributaries of the Assiniboine.

Pip (2000) undertook a very large survey of freshwater molluscs in Manitoba in 1998 to compare with results from previous surveys. She resurveyed 302 of 312 sites surveyed about 20 years previously. Although the focus of these surveys was on gastropods, there were results for mussels, in particular, a decline from four to two in the number of sites from which Q. quadrula was recorded. This decline occurred in the 20 year interval from the previous survey. Unfortunately no collecting methodology, site information, or abundance data were reported (Pip 2000).

Carney (2003a, 2004a) collected mussels from sites along the length of ten different rivers in Manitoba. The purpose was to collect tissue for DNA analyses, determine the reproductive status and demographics, and investigate the parasites of the mussels. Permits restricted the number to no more than 20 individuals of any one species from any single site, excepting one reference site on the lower Assiniboine. Once 20 individuals of a species had been collected that species was no longer collected. As a result, collecting effort on common species would stop and the focus would be on the less common species. Nonetheless, time spent searching was noted so effort in terms of p-h could be determined. At no site was the limit for Q. quadrula reached and in fact, effort was focused on this species due to its rarity and absence of evidence for successful production of glochidia.

Carney (2004b) reported the results of a quantitative survey of mussels in the Assiniboine River through Spruce Woods Provincial Park. A total of 620 1 m2 quadrats at 49 transects were searched with no Q. quadrula being recovered. The average density for all species in this study was estimated to be 0.08/m2.

Quadrula quadrula from the Bloodvein River, which drains into the east side of Lake Winnipeg, was reported in 2004 (Staton pers. comm. 2005). A survey in 2010 did not find this species in the Bloodvein, but there is no information on methods. Three sites on the Brokenhead River near its mouth on Lake Winnipeg surveyed in 2013 had between one and three live Q. quadrula recorded, with numbers increasing with distance from the lake. Because there is no information on effort or methods, it is difficult to reach any conclusions on this apparent trend. A more extensive survey in July 2015 yielded 30 live animals (Watkinson pers. comm. 2015). There have been no historical surveys of mussels in this, or other rivers, from the east side of Lake Winnipeg. An additional site was also discovered in the Wanipigow River in 2015. Three live animals were found here, but no information on survey methods are currently available.

In 2007, a mussel relocation project was undertaken in association with bridge construction over the Assiniboine River at Brandon. Four adult individuals were discovered. It had been thought that the historical range in the Assiniboine River, which extended to the Shellmouth Dam (northwestern-most dot in Figure 6), had contracted to the Portage Diversion (directly north of Portage la Prairie, Figures 6 and 7). The discovery of Q. quadrula in Brandon, well above the Portage Diversion, indicates this species is still present in the upper Assiniboine and its distribution may extend to its historical range. Confirmation of this, and assessment of any subpopulations that exist above the Portage Diversion, would require considerable effort due to the size, turbidity, and current of the Assiniboine River. Fisheries and Oceans Canada conducted a mussel identification workshop on the Assiniboine River in 2009 that recorded a single live Q. quadrula at a site where it had been previously collected.

New surveys in Manitoba began in 2011 on the LaSalle River, a tributary of the Red River, near La Barriere Park, under the direction of DFO (Morris pers. comm. 2015); Quadrula quadrula was recorded in 2011 (1 individual), 2013 (3 individuals), and 2014 (29 individuals). No information on effort or methodology is currently available. Cooks Creek, a tributary of the Red River near Selkirk, was surveyed in 2013 and 2014. Seven live Q. quadrula were recorded in 2013 and a single individual was recorded in 2014 (Morris pers. comm. 2015). The Rat River, also a tributary of the Red River, had Q. quadrula recorded in 2013 with a single individual being observed (Morris pers. comm. 2015). This was recorded near St. Pierre Jolys, which is quite a distance upstream from the confluence with the Red River. Due to dangerous sampling conditions, no live individuals have been recovered from the Red River itself, although fresh shells were reported in 2013 (Morris unpubl. data). These data are encouraging; however, these sites fall within the existing EOO for this species, but do increase the IAO compared to the previous COSEWIC report.

Abundance

Estimating the density of Q. quadrula in Manitoba is possible only for the lower Assiniboine River using the results reported by Scaife and Janusz (1992). As described previously, they recovered 62 Q. quadrula from 24 of the 120 quadrats using SCUBA. This would result in an average density of 0.52 Q. quadrula/m2. This should be considered an upper bound inasmuch as Carney (2004b) reported an average density of 0.08/m2 for all mussel species from a larger survey on a different shallower stretch of the Assiniboine River sampled by wading from shore to shore.

If 0.52/m2 is accepted as an approximate upper estimate of the density of Q. quadrula, then the subpopulation size within this stretch of the Assiniboine River can be estimated. The biological area of occupancy (AO), based on the length of the occupied reach (150 km) times the mean width of the reach (50 m), for this stretch of the Assiniboine River is 7.5 km2. A density of 0.52 per m2 yields an estimated total subpopulation of 3,900,000 individuals in this river. This should be considered an extreme upper limit because long stretches of the Assiniboine have a substrate of drifting soft sand, unsuited as mussel habitat as reflected in the much lower density values for all species reported by Carney (2004b) in such stretches. Furthermore, Watson et al. (1998) only recovered Q. quadrula from 27% of sites along the Assiniboine River. This many samples along the Assiniboine without Q. quadrula clearly indicates that this species does not occur along the entire length of this river. Using this value (27%) to calculate the proportion of the river suitable for Q. quadrula yields a revised subpopulation estimate of 1,050,000 individuals. Thus the Q. quadrula subpopulation in the Assiniboine River is estimated to be between 1 and 4 million individuals, with the lower limit seeming more credible. These widely divergent numbers only serve to highlight the pressing need for more data on mussels from this, and the other Manitoba watersheds.

There are no data amenable to estimating Q. quadrula subpopulation sizes in the Red or Roseau rivers. Live specimens have not been recovered from the Red River since the investigations reported by Clarke (1973). The last live specimen from the Roseau was one individual collected in 1992 (Carney unpubl. data). Six other individuals were recorded by Manitoba Fisheries staff in 1991 from the lower Roseau (Erickson pers. comm. 2005). It seems probable they exist in the Red River simply based on the size of the river; but there is no basis for this supposition in the Roseau River. The absence of regular collection information from the Bloodvein River, Brokenhead River, Cooks Creek, LaSalle River, Red River, or Rat River, and the paucity of abundance data, precludes any attempt to estimate abundance trends in these rivers. These data are useful for presence/absence of the species and do contribute to our increasing knowledge of the distribution of Q. quadrula in Manitoba.

Neither Watson et al. (1998) nor Scaife and Janusz (1992) reported size values for the mussels they collected. All individuals collected by Carney (2003a) were measured and aged using thin sections but only lengths of mussels collected from the Assiniboine River are presented (Figure 15), to maintain consistency with the data presented for Ontario. Specimens ranged in size from 53 mm to 123 mm (mean = 101 mm). There was an absence of small individuals, which seems to be the common situation for the Manitoba population (Carney pers. obs.). The absence of smaller individuals, even in the range of 50-100 mm, is indicative of little or no recruitment. Carney (2003a, unpubl. data) has only ever recovered two female Q. quadrula gravid with glochidia. This apparent lack of reproduction is consistent with little or no recruitment.

Figure 15. Size frequency distribution for Quadrula quadrula collected from the Assiniboine River, Manitoba. Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size frequency distribution for Quadrula quadrula collected from the Assiniboine River, Manitoba
Photo: © Carney 2003a
Long description for Figure 15

Chart illustrating size frequency distribution for Mapleleaf collected from the Assiniboine River, Manitoba.

Fluctuations and trends

Clarke (1973) indicated that Q. quadrula was relatively common to abundant (Table 2, page 12) on the one hand, but in the text indicated it was “…ordinarily uncommon…” (page 33). Where Clarke (1973) does provide collecting data, the numbers collected within Manitoba are never very high. Current information is consistent with Q. quadrula being uncommon. Watson et al. (1998) surveyed the greatest number of sites in the lower Assiniboine River (below the Portage Diversion) and recorded the presence of Q. quadrula at 27% of the sites examined, recovering just six individuals over 157 km of river with an estimated CPUE of 0.66 (Table 5). Comparisons of CPUE indicate subpopulation densities are quite variable, even within rivers, from a low of 0 in the Red and Roseau rivers to a high of 1.5 in the Assiniboine (Table 5). In 2003 Watkins (unpubl. data) surveyed six sites in the Assiniboine within Winnipeg for 19.5 p-h with a CPUE of 1.54 (range 0-9). In 2004 Carney and Watkins (unpubl. data) resurveyed one of these sites (which had a CPUE = 9) for 3 p-h and recorded a CPUE of 0.37, more than an order of magnitude below the value of the previous year. The available data indicate Q. quadrula abundance is the highest in the Assiniboine River within and near the western perimeter of Winnipeg and then decreases proceeding upstream to the Portage Diversion and downstream toward the confluence with the Red River. Just a single individual has been documented from the almost 900 km of the Assiniboine upstream of the Portage Diversion (Carney 2003a).

Historical records indicate a distribution that includes the Red River and many tributaries, the length of the Assiniboine River to Lake of the Prairies, and many sites in Lake Winnipeg (Figure 6). In the time period from 1992-2004, Q. quadrula has only been recorded from about half the length of the Assiniboine River, with the Portage Diversion representing a line of demarcation. The discovery of Q. quadrula in 2007 at Brandon suggests that the distribution may not have been reduced. The abundance status of any subpopulations above the Portage Diversion remain unknown. No live specimens have recently been recovered from the Red River or from Lake Winnipeg (Figure 7; black dot just south of Winnipeg is from multiple records along the La Salle River while those north of Winnipeg are from Cooks Creek, both tributaries of the Red River).

Quadrula quadrula is likely declining in abundance within Manitoba. Clarke (1973) reported Q. quadrula from the Roseau River. Since then six individuals have been recorded in 1991 (Erickson pers. comm. 2005) and one individual in 1992 (Carney unpubl. data). No live Q. quadrula have been recently observed in the Red River (Carney 2004a; Carney and Watkins unpubl. data) although fresh shells were reported in 2013 (Morris unpubl. data). Clarke (1973) reported collecting 25 Q. quadrula from the Red River at St. Jean Baptiste. During exceptionally low water in 2003, Carney (2004a) was able to sample the entire width of the river at the same site and found no living specimens, but observed many empty valves along the shore. None of these valves were fresh. In 2004, Carney and Watkins (unpubl. data) returned to this, and other sites along the Red from which Clarke (1973) had collected Q. quadrula and found just a few, highly weathered empty valves. Although the Red River is exceptionally difficult to sample, the fact that Clarke was able to collect 25 live individuals, and nobody has subsequently, strongly suggests there has been a decline in abundance of Q. quadrula within the Red River in Manitoba.

The additional sites reported to harbour Q. quadrula only add dots within the previously known distribution of the species, and these are in tributaries of the Red River and Lake Winnipeg. The absence of any report of this species in Lake Winnipeg (Pip pers. comm. 2004) suggests it has been lost from this lake; the Zebra Mussel invasion will prevent it re-establishing. The overall abundance can still be declining even with new sites being discovered. If the species’ abundance is declining, newly discovered sites do not negate the decline. Size class data collected prior to 2003 showed an apparent lack of recruitment throughout the Assiniboine (Figure 15) and was consistent with a population that is maintaining its distribution but slowly senescing. However, data collected from 2013 to 2015 from across the range in Manitoba (including 24 specimens from the Assiniboine) show evidence of recent recruitment (Figure 16). The continuing decline in water quality and new threat caused by Zebra Mussels all lead to a defensible conclusion that the abundance may be in decline, new sites not withstanding.

Figure 16. Size class distribution for live Quadrula quadrula collected from across its range in Manitoba from 2013 to 2015 (n = 118). Specimens <50 mm are considered juveniles and indicative of recent recruitment.
Size class distribution for live Quadrula quadrula collected from across its range in Manitoba
Long description for Figure 16

Chart illustrating size class distribution for live Mapleleaf collected from across its range in Manitoba from 2013 to 2015.

Rescue effect

The Red River drainage is part of the Hudson Bay drainage with no natural connection to the adjacent Mississippi River drainage. Thus there could be no natural rescue of the populations in the Red River drainage from populations in the Mississippi/Missouri drainages to the east and south, respectively. Although Manitoba subpopulations appear to occur as widely separated assemblages of individuals, there are few barriers limiting the movement of potential fish hosts, and as such, Q. quadrula can reasonably be considered to be a single, diffuse population in Manitoba. The Portage Diversion on the Assiniboine River, locks on the Red River at Lockport, and lowhead dams on the Roseau represent the only barriers to fish movement within the extent of occurrence in Manitoba. The Portage Diversion is an impassable barrier and represents a complete barrier for the upstream dispersal of glochidia-infested hosts.

The status of this species in the North Dakota and Minnesota portions of the Red River drainage are not well known. There is no information from North Dakota (Dyke pers. comm. 2004). Carney (2003b) did not encounter this species from sites in North Dakota reported by Cvancara (1970) to hold Q. quadrula. Limited investigations in the upper Red River undertaken by Minnesota Department of Natural Resources staff recovered just three Q. quadrula (Davis pers. comm. 2004). A survey by Hart (1995) of the Otter Tail River, a tributary of the Red River in Minnesota, recovered just ten Q. quadrula from a total of 4,851 individual mussels. A project to translocate mussels from two bridge construction sites on the Otter Tail River (Ceas 2001) reported no Q. quadrula. This would essentially be a census of the mussels from these two sites. These reports suggest that Q. quadrula is an uncommon component of the mussel fauna of the Red River drainage in Manitoba, North Dakota, and Minnesota. The known mobility of Channel Catfish potential hosts (Stewart and Watkinson 2004) within the Red River suggests a limited capacity for rescue from populations within the Red River system outside Manitoba. However, the current evidence indicates that there are few populations in North Dakota and Minnesota to act as a source for rescue. In addition, American populations within the Red River drainage in North Dakota and Minnesota have been subject to the same inferred population declines as in Manitoba (Hart 1995; Ceas 2001; Carney 2003b).

Threats and limiting factors

Threats

The IUCN Threats Calculator (Master et al. 2009) determined the impacts from standardized threats categories. Impacts are calculated by scoring the scope (proportion of the Canadian population exposed to the specific threat in the next 10 years), severity (percent reduction in the proportion of the population exposed to the threat caused by the threat in the next three generations), and timing of the various threats. While the overall calculated impact for the Great Lakes - Upper St. Lawrence population (Table 6) yielded a range of high-medium, it was adjusted to medium impact, meaning a population decline of between 3 and 30% is expected in the next three generations caused by the various threats acting in the next 10 years. Similarly, the overall calculated impact for the Saskatchewan - Nelson Rivers population (Table 7) yielded a range of very high to low, but was adjusted to high, meaning a 10 to 70% decline is projected for the next three generations caused by the various threats acting in the next 10 years; there was much uncertainty in the magnitude of the impact from the Zebra Mussel invasion. These overall threat impacts are the only means currently available for projecting future population declines. Threats are arranged from the highest to lowest calculated impact for each DU.

Table 6. Threats assessment for Great Lakes - Upper St. Lawrence population of Quadrula quadrula.

Threats assessment worksheet

Species or ecosystem scientific name:
Mapleleaf (Quadrula quadrula) Great Lakes - Upper St. Lawrence population
Date:
8/19/2015
Assessor(s):
Dwayne Lepitzki (facilitator, responsible co-chair), Dave Zanatta (co-writer), Jordan Hoffman (co-writer), Joe Carney (co-writer), Todd Morris (SSC, DFO), Doug Watkinson (DFO), Sarah Hogg (OMNRF), Daelyn Woolnough (SSC), Andrew Hebda (SSC)
References:
Draft threats assessment based on draft status report; formal threats assessment occurred on 19 August 2015 using updated range maps
Overall threat impact calculation help:
Threat impactThreat impact (descriptions)Level 1 Threat impact counts:
high range
Level 1 Threat impact counts:
low range
AVery high00
BHigh00
CMedium20
DLow24
-Calculated overall threat impact:HighMedium
Assigned overall threat impact:
C = Medium
Impact adjustment reasons:
Medium (3-30% decline) makes more sense than High (10-70% decline) even given the accumulated impacts, especially because this species does seem to survive in eutrophic waters. Climate change impact is unknown for now, especially in the short term.
Overall threat comments
All locations in DU are impacted by dreissenid infestation and/or agriculture runoff.
Table 6b. Threats assessment for Great Lakes - Upper St. Lawrence population of Quadrula quadrula.
ThreatImpact (calculated)Scope (next 10 Yrs)Severity (10 Yrs or 3 Gen.)TimingComments
1Residential & commercial developmentblankblankblankblank
1.1Quadrula quadrulaHousing & urban areasblankblankblankblank
1.2Quadrula quadrulaCommercial & industrial areasblankblankblankblank
1.3Quadrula quadrulaTourism & recreation areasblankblankblankblank
2Agriculture & aquacultureblankblankblankblank
2.1Quadrula quadrulaAnnual & perennial non-timber cropsblankblankblankblank
2.2Quadrula quadrulaWood & pulp plantationsblankblankblankblank
2.3Quadrula quadrulaLivestock farming & ranchingblankblankblankblank
2.4Quadrula quadrulaMarine & freshwater aquacultureblankblankblankblank
3Energy production & miningblankblankblankblank
3.1Quadrula quadrulaOil & gas drillingblankblankblankblank
3.2Quadrula quadrulaMining & quarryingblankblankblankblank
3.3Quadrula quadrulaRenewable energyblankblankblankblank
4Transportation & service corridorsDLowSmall (1-10%)Extreme (71-100%)
4.1Quadrula quadrulaRoads & railroadsblankblankblankblank
4.2Quadrula quadrulaUtility & service linesblankNegligibleNegligible (<1%)Negligible (<1%)
4.3Quadrula quadrulaShipping lanesDLowSmall (1-10%)Extreme (71-100%)
4.4Quadrula quadrulaFlight pathsblankblankblankblank
5Biological resource useblankNegligibleNegligible (<1%)Unknown
5.1Quadrula quadrulaHunting & collecting terrestrial animalsblankblankblankblank
5.2Quadrula quadrulaGathering terrestrial plantsblankblankblankblank
5.3Quadrula quadrulaLogging & wood harvestingblankblankblankblank
5.4Quadrula quadrulaFishing & harvesting aquatic resourcesblankNegligibleNegligible (<1%)Unknown
6Human intrusions & disturbanceblankNegligibleLarge (31-70%)Negligible (<1%)
6.1Quadrula quadrulaRecreational activitiesblankNegligiibleLarge (31-70%)Negligible (<1%)
6.2Quadrula quadrulaWar, civil unrest & military exercisesblankblankblankblank
6.3Quadrula quadrulaWork & other activitiesblankNegligibleNegligible (<1%)Negligible (<1%)
7Natural system modificationsCDMedium - LowRestricted (11-30%)Moderate - Slight (1-30%)
7.1Quadrula quadrulaFire & fire suppressionblankblankblankblank
7.2Quadrula quadrulaDams & water management/useblankNegligiblePervasive (71-100%)Negligible (<1%)
7.3Quadrula quadrulaOther ecosystem modificationsCDMedium - LowRestricted (11-30%)Moderate - Slight (1-30%)
8Invasive & other problematic species & genesDLowPervasive (71-100%)Slight (1-10%)
8.1Quadrula quadrulaInvasive non-native/alien speciesDLowPervasive (71-100%)Slight (1-10%)
8.2Quadrula quadrulaProblematic native speciesblankNegligibleNegligible (<1%)Extreme (71-100%)
8.3Quadrula quadrulaIntroduced genetic materialblankblankblankblank
9PollutionCDMedium - LowPervasive (71-100%)Moderate - Slight (1-30%)
9.1Quadrula quadrulaHousehold sewage & urban waste waterDLowPervasive (71-100%)Slight (1-10%)
9.2Quadrula quadrulaIndustrial & military effluentsCDMedium - LowPervasive (71-100%)Moderate - Slight (1-30%)
9.3Quadrula quadrulaAgricultural & forestry effluentsDLowPervasive (71-100%)Slight (1-10%)
9.4Quadrula quadrulaGarbage & solid wasteblankblankblankblank
9.5Quadrula quadrulaAir-borne pollutantsblankblankblankblank
9.6Quadrula quadrulaExcess energyblankblankblankblank
10Geological eventsblankblankblankblank
10.1Quadrula quadrulaVolcanoesblankblankblankblank
10.2Quadrula quadrulaEarthquakes/tsunamisblankblankblankblank
10.3Quadrula quadrulaAvalanches/landslidesblankblankblankblank
11Climate change & severe weatherblankUnknownPervasive (71-100%)Unknown
11.1Quadrula quadrulaHabitat shifting & alterationblankblankblankblank
11.2Quadrula quadrulaDroughtsblankblankblankblank
11.3Quadrula quadrulaTemperature extremesblankblankblankblank
11.4Quadrula quadrulaStorms & floodingblankblankblankblank

Threats to the Great Lakes - Upper St. Lawrence population (table 6)

Pollution (threat 9: impact medium - low)

Strayer and Fetterman (1999) identify non-point source input of nutrients, sediments, and toxins as the major threats to unionid mussels, with agricultural activities as the major contributor. Agricultural activity comprises 75% of land use in the Grand River basin and about 80% of land use within the Sydenham and the Thames river basins. Nutrients have been recorded to be consistently above accepted standards in the Sydenham basin. Dams and siltation are of concern in the Thames watershed. The pattern is the same in the Ausable River with approximately 80% of the land being used for agriculture, and suspended solids and nutrient levels exceed federal guidelines. There is also an expectation of increasing human populations within these watersheds resulting in increased urbanization with concomitant effects on water quality (see Habitat Trends in Ontario). Most of the Q. quadrula subpopulations are in areas of high agricultural and or urban land use and are exposed to runoff; however, with most and the largest subpopulations appearing relatively stable and apparently reproducing, it appears Q. quadrula may be tolerant of chronic exposure to high nutrients and suspended solids. At worst, agricultural effluents may be causing a slow decline.

Spills from pipelines (e.g., petroleum products), rail, and industrial sources appear to have the greatest potential toxic impact. The entire DU has the potential to be exposed to industrial spills, with potentially moderate to slight impacts, depending on the magnitude and type of spill. This type of toxic exposure would be brief but potentially catastrophic.

Natural system modifications (threat 7: impact medium - low)

Dreissenid mussels compete with unionids for food and modify habitat making it less hospitable to unionid mussels (details below). Up to 30% of all Q. quadrula in this DUare potentially impacted by this threat.

Invasive and other problematic species (threat 8: impact low)

Smothering by dreissenids and predation by Round Goby have the potential to impact the entire DU. Dreissenids are present in low numbers in both the Thames and Grand rivers and have the potential to impact >50% of all Q. quadrula in the DU. Round Goby is present in low numbers in all of the sites, but the impact of predation on juvenile Q. quadrula, if any, is unknown.

Many mussel species within the Great Lakes have had local subpopulations destroyed by the establishment of the invasive Zebra Mussel (Schlosser et al. 1996). Zebra Mussels attach to the unionid mussel shell and impair burrowing, movement, feeding, respiration, and other physiological activities (Haag et al. 1993; Baker and Hornbach 1997). This impairment results in the death of the unionid mussel. Because Zebra Mussel has such explosive population growth they can effectively eliminate entire unionid mussel subpopulations in a very short time as a result of direct fouling and competition for food and modification of habitat. The evidence indicates that Q. quadrula has been largely extirpated from Lake Erie, Lake St. Clair, and the Niagara and Detroit rivers as a result of infestations by the Zebra Mussel. Reports of Zebra Mussel from the Fanshawe Reservoir on the Thames River indicate the subpopulations of Q. quadrula in this river may be threatened by this invasive species (Maskant 2004). Zebra Mussel is still considered a serious threat to Q. quadrula and all unionid mussel species. However, the Great Lakes - Upper St. Lawrence population of Q. quadrula may now be past the worst stage of the dreissenid invasion and coexistence may be possible where dreissenid densities are lower (Lucy et al. 2014). The newly discovered sites in coastal embayments of western Lake Ontario are in close proximity to waters that are heavily infested with dreissenid mussels. However, only limited numbers of dreissenid (Zebra and Quagga mussels) were seen infesting the shells of Q. quadrula in these areas and it seems that the threat severity is only slight.

Round Gobies are another potential threat to unionids as they feed on juvenile unionids and compete with some hosts for space and predate on eggs (Poos et al. 2010). They could also be a population sink for glochidia. The overall threat impact to Q. quadrula may only be slight as catfish also predate on gobies and the shell of even juvenile Q. quadrula may be too thick for gobies to crush. The result is that this may only be a negligible impact threat.

Transportation and service corridors (threat 4: impact low)

Dredging the benthos to deepen shipping lanes, harbours, and marinas in the lower Grand River, and in coastal habitats in western Lake Ontario occurs frequently. Approximately one third of the estimated population is found in the lower Grand River and up to 10% of the total Q. quadrula population could be affected by this type of impact.

Threats to the Saskatchewan-nelson Rivers population (table 7)

Invasive and other problematic species (threat 8: impact high - low)

The invasive Zebra Mussel is considered to be established in the Red River and Lake Winnipeg (Watkinson pers. comm. 2015). The first discovery of Zebra Mussels in the Red River drainage was in Pelican Lake, Minnesota in 2009 (Owen 2015). By 2010 they had migrated 120 km to Wahpeton North Dakota on the Red River. This is 800 km south of the Manitoba border, but it is upstream so it was inevitable that Zebra Mussels would continue their migration down the Red River and into Manitoba. Zebra Mussels were discovered in harbours at Balsam Bay, Gimli, Silver Harbour, and Winnipeg Beach in 2013 (Watkinson pers. comm. 2015). These harbours were “bulk treated” with liquid potash to kill the mussels. This was apparently successful in those sites, but in August 2014 Zebra Mussels were found in other parts of the south basin. High numbers of veligers were reported in early 2015 in the Red River where it enters Manitoba at Emerson from North Dakota (Watkinson pers. comm. 2015), and adults have been reported at a boat launch in Selkirk and attached to Pink Heelsplitters (Potamilus alatus) as part of a mussel relocation associated with a pipeline crossing of the Red River (Watson pers. comm. 2015). Therriault et al.’s (2013) risk assessment concluded that the largest ecological impacts associated with dreissenid invasions were negative impacts on biota that inhabit the offshore zones of lakes or rivers, for example, losses in productivity for phytoplankton, zooplankton, and planktivorous fishes, and to unionid mussels, with effects on the latter being severe declines in abundance and biodiversity. The Great Lakes are an example of what can happen when Zebra Mussel invades (see this same threat impact for the other DU). It seems reasonable to predict that native unionid populations in the Red River and Lake Winnipeg will decline, but the magnitude of the decline within the next three generations caused by the threat acting in the next 10 years is uncertain, hence the large range for the severity (Table 7). Some small pockets will most likely survive the initial infestation. The major concern is if Zebra Mussel becomes established in the Assiniboine River. This is possible if Zebra Mussel manages to be introduced into the Shellmouth Reservoir near the headwaters of the Assiniboine River. This seems probable as a result of movement of boats between watersheds. Fishing is popular in the Red River, Lake Winnipeg, and in the Shellmouth Reservoir. It is simply a matter of time for a boat contaminated with Zebra Mussel veliger larvae in the bilge water or trailer frame to move from an infested site to the Shellmouth Reservoir. Once in the Shellmouth, this source of Zebra Mussel larvae will continually seed the rest of the Assiniboine, with the expected demise of the local unionid mussel fauna.

Table 7. Threats assessment for Saskatchewan - Nelson Rivers population of Quadrula quadrula.

Threats assessment worksheet

Species or ecosystem scientific name:
Mapleleaf (Quadrula quadrula) Saskatchewan - Nelson Rivers population
Date:
8/19/2015
Assessor(s):
Dwayne Lepitzki (facilitator, responsible co-chair), Dave Zanatta (co-writer), Jordan Hoffman (co-writer), Joe Carney (co-writer), Todd Morris (SSC, DFO), Doug Watkinson (DFO), Sarah Hogg (OMNRF), Daelyn Woolnough (SSC), Andrew Hebda (SSC)
References:
Draft threats assessment based on draft status report; formal threats assessment occurred on 19 August 2015 using updated range maps
Overall threat impact calculation help:
Threat impactThreat impact (descriptions)Level 1 Threat impact counts:
high range
Level 1 Threat impact counts:
low range
AVery high00
BHigh10
CMedium20
DLow03
-Calculated overall threat impact:Very highLow
Assigned overall threat impact:
B = High
Impact adjustment reasons:
Based on the potential threat from Zebra Mussels (10 - 70% decline is expected in the next 3 generations) coupled with the other threats
Overall threat comments
Entire DU threatened by agricultural impacts. Zebra Mussel infestation throughout DU is unlikely within the next 10 years.
Table 7. Threats assessment for Saskatchewan - Nelson Rivers population of Quadrula quadrula
ThreatImpact (calculated)Scope (next 10 Yrs)Severity (10 Yrs or 3 Gen.)TimingComments
1Residential & commercial developmentblankNegligibleNegligible (<1%)Negligible (<1%)
1.1Housing & urban areasblankblankblankblank
1.2Commercial & industrial areasblankblankblankblank
1.3Tourism & recreation areasblankNegligibleNegligible (<1%)Negligible (<1%)
2Agriculture & aquacultureblankblankblankblank
2.1Annual & perennial non-timber cropsblankblankblankblank
2.2Wood & pulp plantationsblankblankblankblank
2.3Livestock farming & ranchingblankblankblankblank
2.4Marine & freshwater aquacultureblankblankblankblank
3Energy production & miningblankblankblankblank
3.1Oil & gas drillingblankblankblankblank
3.2Mining & quarryingblankblankblankblank
3.3Renewable energyblankblankblankblank
4Transportation & service corridorsblankNegligibleNegligible (<1%)Negligible (<1%)
4.1Roads & railroadsblankNegligibleNegligible (<1%)Negligible (<1%)
4.2Utility & service linesblankNegligibleNegligible (<1%)Negligible (<1%)
4.3Shipping lanesblankblankblankblank
4.4Flight pathsblankblankblankblank
5Biological resource useblankNegligiblePervasive (71-100%)Negligible (<1%)
5.1Hunting & collecting terrestrial animalsblankblankblankblank
5.2Gathering terrestrial plantsblankblankblankblank
5.3Logging & wood harvestingblankblankblankblank
5.4Fishing & harvesting aquatic resourcesblankNegligiblePervasive (71-100%)Negligible (<1%)
6Human intrusions & disturbanceblankNegligibleRestricted (11-30%)Negligible (<1%)
6.1Recreational activitiesblankNegligibleRestricted (11-30%)Negligible (<1%)
6.2War, civil unrest & military exercisesblankblankblankblank
6.3Work & other activitiesblankNegligibleNegligible (<1%)Negligible (<1%)
7Natural system modificationsCDMedium - LowLarge (31-70%)Moderate - Slight (1-30%)
7.1Fire & fire suppressionblankblankblankblank
7.2Dams & water management/useblankNegligibleLarge (31-70%)Negligible (<1%)
7.3Other ecosystem modificationsCDMedium - LowLarge (31-70%)Moderate - Slight (1-30%)
8Invasive & other problematic species & genesBDHigh-LowLarge (31-70%)Serious - Slight (1-70%)
8.1Invasive non-native/alien speciesBDHigh-LowLarge (31-70%)Serious - Slight (1-70%)
8.2Problematic native speciesblankblankblankblank
8.3Introduced genetic materialblankblankblankblank
9PollutionCDMedium-LowLarge (31-70%)Moderate - Slight (1-30%)
9.1Household sewage & urban waste waterDLowPervasive (71-100%)Slight (1-10%)
9.2Industrial & military effluentsCDMedium - LowLarge (31-70%)Moderate - Slight (1-30%)
9.3Agricultural & forestry effluentsDLowPervasive (71-100%)Slight (1-10%)
9.4Garbage & solid wasteblankblankblankblank
9.5Air-borne pollutantsblankblankblankblank
9.6Excess energyblankblankblankblank
10Geological eventsblankblankblankblank
10.1Volcanoesblankblankblankblank
10.2Earthquakes/tsunamisblankblankblankblank
10.3Avalanches/landslidesblankblankblankblank
11Climate change & severe weatherblankUnknownPervasive (71-100%)Unknown
11.1Habitat shifting & alterationblankblankblankblank
11.2Droughtsblankblankblankblank
11.3Temperature extremesblankblankblankblank
11.4Storms & floodingblankblankblankblank

Natural system modifications (threat 7: impact medium - low)

Much of the Red and Assiniboine river systems have been diked and/or had rip rap placed in the embankments to act as flood controls. Rip rap destroys mussel habitat by burying the clay and cobble with large boulders. Dikes and rip rap both can alter the hydrology in ways that are detrimental to mussel survival (Libois and Hallet-Libois 1987; Watters 1999). The arrival of Zebra Mussel not only has a direct effect on Q. quadrula, but also has indirect effects including outcompeting the native mussel species and altering the habitat (Ward and Ricciardi 2013).

Pollution (threat 9: impact medium - low)

Elevated nutrients and pollutants in the water represent a present and ongoing threat to Q. quadrula. Point source inputs, such as household sewage and urban wastewater from Brandon, Portage La Prairie, Winnipeg, and Grand Forks and Fargo, North Dakota as well as industrial effluents associated with the Brandon meat packing plant, and industry in Winnipeg are sources of effluents that are demonstrated to cause harm to freshwater mussels (Gillis 2012; Gillis et al. 2014). Non-point source agricultural effluents from Saskatchewan, Manitoba, North Dakota, and Minnesota into the Red and Assiniboine river systems contribute nutrients and toxins that are major threats to unionid mussels (Strayer and Fetterman 1999). Phosphorus and nitrogen loads in these systems exceed legal standards (Environment Canada 2011). These elevated nutrient loads have been shown to be important factors that limit freshwater mussel populations (Augspurger et al. 2003; Bartsch et al. 2003; Mummert et al. 2003)

Limiting factors

The major natural limitation to distribution and abundance of freshwater mussels is the availability, distribution, and abundance of the host fish required for successful completion of the life cycle. If the host fish is absent then there can be no recruitment. If a mussel species is long-lived, persistence of adult populations can lead to the illusion of a healthy mussel population despite the lack of recruitment due to a missing host fish. Because Q. quadrula is relatively long-lived, it is evidence of recruitment that would indicate a healthy viable population, not just the presence of adult mussels. The known host fishes for Q. quadrula include the Channel Catfish and Flathead Catfish. Channel Catfish is a common species in Ontario and in Manitoba and this should not limit the possibility for successful reproduction by Q. quadrula. However, fish populations should be monitored to ensure mussel reproduction is possible.

Number of locations

Ontario

The major threats (Table 6) for the Great Lakes - Upper St. Lawrence population are: Pollution from agricultural, municipal, and industrial sources (Medium-Low impact), Natural system modifications (Medium-Low impact, including effects on the habitat caused by dreissenids), and Invasive species (Low impact - primarily dreissenid mussel infestation). A spill (agricultural, industrial, or other) is likely the most serious plausible event that could define the number of locations. All of the subpopulations, defined by water body (Table 1), are exposed to the ongoing threat of a toxic effluent spill, which suggests at least 21 locations. Only 11 (Thames River, Grand River, Jordan Harbour, Sixteen Mile Creek, Fifteen Mile Creek/Pond, Cootes Paradise, Coyle Creek, St. Clair Delta, Bayfield River, Lake Henry/Pelee Island, Rondeau Bay) of the 21 subpopulations are currently under the threat of infestation by dreissenid mussels. This is because the other ten subpopulations in streams and rivers lack any upstream source population (in a lake or impoundment) that would produce dreissenid veligers to infest downstream unionid populations.

Manitoba

The major threats (Table 7) for the Saskatchewan - Nelson Rivers population are: Invasive species (High-Low Impact, dreissenid mussel infestation), Natural system modifications (Medium-Low impact, dreissenid mussels and river bank hardening), and Pollution (Medium-Low impact, urban, agricultural, and industrial activities). These threats suggest that there are currently 7-11 locations in Manitoba (Table 2). The threat from non-point source pollution exists in the Red River (including the Seine River, La Salle River, and Cooks Creek tributaries), the Rat River (although it could be considered part of the Red River location as it is a tributary of the Red River), and the Assiniboine River (above and below the Portage Diversion dam) each representing single locations (n=3). Each of the Brokenhead, Wanipigow, Bloodvein, and Bradbury rivers (all drain into the eastern edge of Lake Winnipeg separate from the Red River) represent separate locations (n=4) because they are not subject to the same magnitude or sources of pollution. Therefore, there are seven locations based on the threats from pollution and Zebra Mussels. The threat associated solely with Zebra Mussels results in 11 locations, assuming each occupied waterbody will not be affected simultaneously by the infestation: Red River, La Salle River, Seine River, Rat River, Cooks Creek, Assiniboine River above the Portage Diversion, Assiniboine River below the Portage Diversion, Brokenhead River, Wanipigow River, Bloodvein River and Bradbury River. The tributaries of the Red are treated as different locations because they are upstream of the Red River, and the Assiniboine is counted as two locations, one upstream and one downstream of the Portage Diversion.

Protection, status and ranks

Legal protection and status

Quadrula quadrula in both Ontario (Great Lakes - Upper St. Lawrence DU) and Manitoba (Saskatchewan - Nelson Rivers DU) is listed under Schedule 1 of Canada’s Species at Risk Act (SARA). The act prohibits killing or capturing listed Endangered or Threatened species, and protects critical habitat, when it is identified. A Recovery Strategy and Action Plan for the Ontario DU has been proposed (Fisheries and Oceans Canada 2016) and identifies critical habitat and key actions that will be implemented.

Ontario is one of six provinces that have stand-alone endangered species acts. Species designated as endangered are protected from willful destruction under these acts. Quadrula quadrula is currently listed as Threatened under Ontario’s Endangered Species Act. Collection of live mussels is considered “fishing” and falls under the Ontario Fishery Regulations made under the federal Fisheries Act. This means that mussels cannot be collected in Ontario without an authorization from the Ontario MNRF. Threatened and endangered species in Ontario receive policy level protection from development and site alteration through the Provincial Policy Statement under the provincial Planning Act. The Ontario Lakes and Rivers Improvement Act (prohibiting the impoundment or diversion of watercourses that would lead to siltation) also protects mussel habitat, as can the Ontario Endangered Species Act. Stream-side development in Ontario is managed through flood plain regulations enforced by local conservation authorities.

Quadrula quadrula is listed as Endangered under Manitoba’s Endangered Species Act. The purpose of this act is to designate indigenous species as endangered, threatened, extinct or extirpated, to protect and enhance survival of species considered endangered or threatened, and to permit the reintroduction of extirpated species. Under this act no person can cause harm, possess, disturb, or interfere with species that are recognized as endangered, threatened, or reintroduced. Furthermore, habitat or required resources of such species cannot be destroyed, disturbed, or interfered with. It is not permitted to kill, capture, collect, or hold alive such species. Exceptions to this require a permit and include reasons such as scientific investigations and purposes related to protection or reintroduction of such species. Another exception is ministerial discretion based on assurance of protection and preservation of the species, or appropriate measures being established to minimize impact of whatever the activity under consideration might be. Mussels are considered shellfish in Manitoba and fall under the jurisdiction of the Fisheries Branch. Currently, the collection of freshwater mussels in Manitoba requires a permit from the Fisheries Branch.

Non-legal status and ranks

Quadrula quadrula is listed as Secure (G5) in North America; its national status is N5 in the United States (as of 11 May 2006) and Imperilled-Vulnerable (N2N3) in Canada (as of 14 May 2013) (NatureServe 2016). The IUCN Red List of Threatened Species categorizes the species as LR/lc as of August 1996, which means Lower Risk/least concern with the suggestion the rank needs updating (IUCN Species Survival Commission 2016). The national general status of freshwater mussels in Canada was completed in 2004 and updated in 2010 (CESCC 2010); Q. quadrula was ranked as 1 (At Risk) nationally and in both jurisdictions (Manitoba and Ontario) where it occurs. The species is provincially ranked as S2 (Imperilled) by Ontario’s Natural Heritage Information Centre (Enns pers. comm. 2016) and S1 (Critically Imperilled) by the Manitoba Conservation Data Centre (Friesen pers. comm. 2016); NatureServe (2016) suggests it is S2 in both Ontario and Manitoba. Other NatureServe (2016) state ranks for Q. quadrula are: Alabama (S4: Apparently Secure), Arkansas (S5), Illinois (S5), Indiana (S4), Iowa (SNR), Kansas (S4), Kentucky (S4S5), Louisiana (S5), Michigan (SNR: Unranked), Minnesota (SNR), Mississippi (S5), Missouri (S4), Montana (SNA: Not Applicable), Nebraska (SNR), New York (SH: Possibly Extirpated / Historical), North Dakota (S3), Ohio (S5), Oklahoma (S5), Pennsylvania (S1S2), South Dakota (S2), Tennessee (S5), Texas (S3), West Virginia (S2) and Wisconsin (S3).

Habitat protection and ownership

Ontario

Land ownership along the reaches of the Sydenham, Thames, Ausable, and Grand rivers where Q. quadrula occurs is mainly private and in agricultural use. Only three small properties in the Sydenham River watershed, the 7 ha Shetland Conservation Area, the 20 ha Mosa Township forest, and the Moore Wildlife Management Area (on Bear Creek where Q. quadrula are present) are publicly owned and somewhat protected (Andreae pers. comm. 1998). There are 21 natural areas totalling 6,200 ha in the Thames River watershed, but only one - the 16 ha Big Bend Conservation Area - is located in the same reach as Q. quadrula (Thames River Background Study Research Team 1998). Also in this reach are four First Nations’ reserves (Delaware of Moraviantown, Munsee Delaware, Oneida of the Thames, and Chippewa of the Thames) that occupy over 6,700 ha of land along approximately 45 km of the river. The Ausable Bayfield Conservation Authority owns a number of properties totalling 1,830 ha throughout the basin (Snell and Cecile Environmental Research 1995). Less than 3% of the land in the Grand River watershed is publicly owned (GRCA 1998). There are 11 conservation areas, only one of which (Byng Island) is located within Q. quadrula’s range in the river. Recovery strategies and action plans have been implemented for the aquatic ecosystems of the Ausable, Sydenham, and Thames rivers to protect and recover aquatic and semi-aquatic species at risk including fishes, mussels, turtles, and snakes (Ausable River Recovery Team 2005; Sydenham River Recovery Team 2002; Thames River Recovery Team 2004). Many landowners are participating in riparian rehabilitation projects and improved land use practices that will ultimately benefit all aquatic species.

Manitoba

Land ownership on the Assiniboine, Red, and Roseau rivers was determined using GIS from 1:500,000 base maps for the water layer. Land along these rivers is predominately privately owned and in agricultural use. Approximately 19% of the Red River could be considered urban, passing through Winnipeg and Selkirk. With the exception of small towns, the remainder is agricultural. There are no protected lands along the Red River or the Roseau River. Approximately 7% is Crown land, 9% is First Nations’ Reserve land, and the remaining 84% is private land used mostly for agriculture. If the entire length of the Assiniboine River within Manitoba (approximately 1,000 km) is considered, then 84% of the surrounding land is privately held and agricultural, 6% is urban, and approximately 10% flows through either a park or a Wildlife Management Area (WMA). Approximately 60% of these parks or WMAs are designated as protected, meaning mining, logging, hydroelectric development, and other activities that affect wildlife habitat are prohibited. The non-protected parks and WMAs are designated Crown lands without a regulation or order in council specifying that land is to be protected. About half of these designated lands, whether protected or not, lie on one bank of the river, with the opposite bank being privately held. However, if just the stretch of the Assiniboine downstream from the Portage Diversion to the confluence with the Red River is considered, there is only 7% flowing through protected land (Beaudry Provincial Park). The remainder is 80% agricultural and 13% is urban, flowing through Winnipeg.

Acknowledgements and authorities contacted

Funding for the preparation of this update report was provided by Environment and Climate Change Canada through the COSEWIC Secretariat. The original COSEWIC (2006) status report for Mapleleaf in Canada was prepared by J. Metcalfe-Smith, J. Carney, and W. Watkins. The contributions of the original co-writers to this report (as a living document) were critical to its creation and are acknowledged.

Backlund, Doug. November 2004. South Dakota Department of Game Fish and Parks. 523 E. Capitol-Foss Building. Pierre, SD 57501.

Bonneau, Don. November 2004. Iowa State Department of Natural Resources. 502 E 9th Street. Des Moines, IA 50319-0034.

Centre for Indigenous Environmental Resources, Inc. (CIER). June 2005. 3rd Floor - 245 McDermot Avenue Winnipeg, MB Canada R3B 0S6.

Clayton, Janet. November 2004. West Virginia Division of Natural Resources. PO Box 67 Elkins, WV 26421.

Cook, Stan. November 2004. Alabama Department of Conservation and Natural Resources, Wildlife and Fisheries Division. 64 N. Union St. Montgomery, AL 36130

Cummings, Kevin. November 2004. Illinois Natural History Survey. 607 East Peabody Drive, Champaign, IL 61820.

Davis, Mike. November 2004. Minnesota Department of Natural Resources. 100 N. Bismarck Expressway Bismarck, ND 58501-5095

DeShaon, Jeff. November 2004. Ohio Environmental Protection Agency. P.O. Box 1049 Columbus, Ohio 43216-1049.

Dyke, Steve. November 2004. North Dakota Fish and Game. 500 Lafayette Road St. Paul, MN 55155-4040.

Erickson, Martin. November 2005. Manitoba Water Stewardship, Fisheries Branch. 200 Saulteaux Crescent, Winnipeg, MB R3J 3W3

Faiman, Scott. November 2004. Missouri Department of Conservation, Resource Science Center.

Fisher, Brant. November 2004. Indiana Department of Natural Resources, Edinburgh, IN 46124.

Gagnon, Elsa. November 2005. Environment Canada, Evaluation and Information Management. 351 St Joseph Boulevard, Gatineau QC.

Hardon, Mike. November 2004. Kentucky Department of Fish and Wildlife Resources. #1 Game Farm Road Frankfort, KY 40601.

Hayes, Kristin. November 2004. Kansas Department of Wildlife and Parks, Fisheries Division. Pratt, KS 67124.

Howells, Robert. November 2004. Texas Parks and Wildlife Department. 4200 Smith School Road. Austin, TX 78744.

Jones, Bob. November 2004. Mississippi Museum of Natural Science. 2148 Riverside Dr. Jackson MS 39202-11353

Levine, Todd. November 2004. Department of Zoology, Miami University, 212 Pearson Hall, Oxford, OH 45056.

Morris, T.J. Extensive consultations throughout preparation (2014-15). Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences, 867 Lakeshore Rd., Burlington ON L7S 1A1.

Myers, Sandi. November 2004. Pennsylvania Department of Environmental Protection. Harrisburg, PA 17105.

Nicholson, Bev. June 2005. Department of Anthropology, Brandon University. Brandon, MB R7A 6A9.

O’Brien, Cathy. November 2004. New York Department of Environmental Conservation, 625 Albany, NY 12233-4750.

Osborne, Cindy. November 2004. Arkansas Natural Heritage Commission. 323 Center St. Little Rock, AR 72201.

Pip, Eva. May 2004. Department of Biology, University of Winnipeg. 515 Portage Ave. Winnipeg, MB R3B 2E9.

Schainost, Steve. November 2004. Nebraska Game and Parks Commission. 299 Husker Road, Alliance, NE 69301.

Scheidegger, Karl. November 2004. Wisconsin Department of Natural Resources, Bureau of Fish Management and Habitat Protection. 101 S. Webster St. Madison, WI 53717.

Schneider, K. November 2002. Stuyvesant Environmental Consulting, LLC. P.O. Box 169, 16 Frisbee Lane, Syuyvesant Falls, NY 12174.

Staton, Shawn. October 2005. Great Lakes Laboratory for Fisheries and Aquatic Sciences. 87 Lakeshore Rd., Burlington, ON L7R 4A6.

Steuck, Mike. November 2004. Iowa State Department of Natural Resources. 502 E 9th Street. Des Moines, IA 50319-0034.

Sutherland, D., March 2004. Natural Heritage Information Centre, 300 Water Street, 2nd Floor, North Tower. P.O. Box 7000, Peterborough, Ontario K9J 8M5.

Vaughn, Caryn. November 2004. Oklahoma Biological Survey. 111 E. Chesapeake Street. Norman, OK 73019.

Watkinson, Doug. July 2015. Freshwater Institute 501 University Crescent, Winnipeg, Manitoba, R3T 2N6

Watson, Ernest. August 2015. Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, R3T 2N6

Withers, David. November 2004. Tennessee Department of Environment and Conservation. 711 R.S. Gass Blvd. Nashville, TN 37243.

Information sources

ABCA (Ausable Bayfield Conservation Authority). 2013. Watershed Report Cards. Web site: http://www.abca.on.ca/page.php?page=watershed-report-card-2013. [accessed October 2015].

Ausable River Recovery Team. 2005. Recovery strategy for species at risk in the Ausable River: An ecosystem approach, 2005-2010. Ausable Bayfield Conservaiton Authority. 129 pp.

Allen, W.R. 1914. The food and feeding habits of freshwater mussels. Biological Bulletin 27 :127-14.

Allen, W.R. 1921. Studies of the biology of freshwater mussels. Biological Bulletin 40:210-241.

Andreae, M., pers. comm. 1998. Verbal correspondence to J. Metcalfe-Smith. March 1998. Biologist, St. Clair Region Conservation Authority, Strathroy, Ontario.

Augspurger, T., A.E. Keller, M.C. Black, W.G. Cope, and F.J. Dwyer. 2003. Water quality guidance for protection of freshwater mussels (Unionidae) from ammonia exposure. Environmental Toxicology and Chemistry 22:2569-2575.

Baker, F.C. 1918. The relation of shellfish to fish in Oneida Lake, New York. New York State College of Forestry at Syracuse University, Circular:11-34.

Baker, S.M., and D.J. Hornbach. 1997. Acute physiological effects of Zebra Mussel (Dreissena polymorpha) infestation on two unionid mussels, Actinonaias ligamentina and Amblema plicata. Canadian Journal of Fisheries and Aquatic Sciences 54:512-519.

Bartsch, M.R., T.J. Newton, J.W. Allran, J.A. O’Donnell, and W.B Richardson. 2003. Effects of pore-water ammonia on in situ survival and growth of juvenile mussels (Lampsilis cardium) in the St. Croix riverway, Wisconsin, USA. Environmental Toxicology and Chemistry 22:2561-2568.

Berg, D.J., E.G. Cantonwine, W.R. Hoeh, and S.I. Guttman. 1998. Genetic structure of Quadrula quadrula (Bivalvia: Unionidae): little variation across large distances. Journal of Shellfish Research 17:1365-1373.

Bourne, A., N. Armstrong, and G. Jones. 2002. A preliminary estimate of total nitrogen and total phosphorus loading to streams in Manitoba, Canada. Water Quality Management Section. Manitoba Conservation Report No. 2002 - 04. 49 pp.

Bouvier, L.D., and T.J. Morris. 2010. Information in support of a Recovery Potential Assessment of Eastern Pondmussel (Ligumia nasuta), Fawnsfoot (Truncilla donaciformis), Mapleleaf (Quadrula quadrula), and Rainbow (Villosa iris) in Canada. Canadian Science Advisory Secretariat, Research Document 2010/120. Fisheries and Oceans Canada, Burlington, Ontario. vi + 51 pp.

Bunt, C.M., S.J. Cooke, and R.S. McKinley. 2000. Assessment of the Dunnville Fishway for passage of Walleyes from Lake Erie to the Grand River, Ontario. Journal of Great Lakes Research 26:482-488.

Butler, S.E., and D.H. Wahl. 2011. Distribution, movements, and habitat use of channel catfish in a river with multiple low-head dams. River Research and Applications 27:1182-1191.

Cairns, M., pers. comm. 2015. Email correspondence to T. Morris. July 2015. Zone Ecologist - Ontario Parks, Southwest Zone, Ministry of Natural Resources and Forestry, Government of Ontario, London, Ontario.

Carney, J.P. 2003a. Freshwater mussels (Mollusca: Unionidae) in the Assiniboine, Souris and Pembina Rivers, Manitoba: demographics, reproduction and parasitisim. Data report submitted to the Province of Manitoba Conservation Data Centre. 56 pp.

Carney, J.P. 2003b. Freshwater mussels (Mollusca: Unionidae) in the Souris and Pembina Rivers, North Dakota: demographics and parasitism. Data report submitted to the State of North Dakota Game and Fish Department. 17 pp.

Carney, J.P. 2004a. Distributions of freshwater mussels (Mollusca: Unionidae) in the Brokenhead, Birch, La Salle, Roseau and Red Rivers in Manitoba. Data report submitted to the Province of Manitoba Conservation Department. 27 pp.

Carney, J.P. 2004b. A survey of the freshwater mussel (Bivalvia: Unionidae) fauna of the Assiniboine River in Spruce Woods Provincial Park. Data report submitted to the Province of Manitoba Conservation Department and Manitoba Parks. 14 pp.

Ceas, P. 2001. Collection and translocation of mussels from two township bridge reconstruction corridors in Otter Tail County, Minnesota. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resouces. 12 pp.

CESCC (Canadian Endangered Species Conservation Council). 2010. Wild Species: the General Status of Species in Canada. Web site: http://www.wildspecies.ca [accessed October 2015].

Christian, A.D., and B.N. Smith. 2004. Trophic position and potential food sources of 2 species of unionid bivalves (Mollusca: Unionidae) in 2 small Ohio streams. Journal of the North American Benthological Society 23:101-113.

Churchill, E.P., and S.I. Lewis. 1924. Food and feeding in fresh-water mussels. Bulletin of the United States Bureau of Fisheries [Document 963] 39:439-471.

Cicerello, R.R., and G.A. Schuster. 2003. A Guide to the Freshwater Mussels of Kentucky. Kentucky State Nature Preserves Commission Scientific and Technical Series 7:1-62.

Clark, G.R., II. 1980. Study of molluscan shell structure and growth using thin sections. Pp. 603-606. In D.C. Rhoads, and R.A. Lutz (eds.). Skeletal Growth of Aquatic Organisms. Plenum Press, New York, New York, U.S.A. xiii + 750 pp.

Clarke, A.H. 1973. The freshwater molluscs of the Canadian Interior Basin. Malacologia 13:1-509.

Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Sciences/National Museums of Canada, Ottawa, Canada. 446 pp.

Clarke, A.H. 1992. Ontario’s Sydenham River, an important refugium for native freshwater mussels against competition from the Zebra Mussel, Dreissena polymorpha. Malacology Data Net 3:43-55.

Coleman, S.J. 1991. Assessment of fish and fish habitat associated with urban and agricultural areas in the Grand River. M.Sc. dissertation, Trent University, Peterborough, Ontario. 127 pp.

Convey, L.E., J.M. Hanson, and W.C. MacKay. 1989. Size-selective predation on unionid clams by muskrats. Journal of Wildlife Management 53:654-657.

Corriveau, J. P.A. Chambers, and J.M. Culp. 2013. Seasonal variation in nutrient export along streams in the Northern Great Plains. Water air and Soil Pollution 224:1594-1600.

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2006. COSEWIC assessment and status report on the Mapleleaf Quadrula quadrula (Saskatchewan-Nelson population and Great Lakes-Western St. Lawrence population) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 58p.

Crail, T.D., R.A. Krebs, and D.T. Zanatta. 2011. Unionid mussels from nearshore zones of Lake Erie. Journal of Great Lakes Research 37:199-202.

Crossman, E.J., and J.H. Leach. 1979. First Canadian record of a flathead catfish. Canadian Field-Naturalist 93:179-180.

Cummings, K.S., and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5. xii + 194 pp.

Cvancara, A.M. 1970. Mussels (Unionidae) of the Red River Valley in North Dakota and Minnesota U.S.A. Malacologia 10:57-92.

Cvancara, A.M. 1983. Aquatic Mollusks of North Dakota. Report of Investigation No. 78 North Dakota Geological Survey. Fargo, North Dakota. v + 141 pp.

Davis, G.M. 1984. Genetic relationships among some North American Unionidae (Bivalvia): sibling species, convergence, and cladistic relationships. Malacologia 25:629-648.

Davis, M., pers. comm. 2004. Email correspondence to J. Carney. November 2004. Minnesota Department of Natural Resources. 100 N. Bismarck Expressway Bismarck, North Dakota 58501-5095

Detweiler, J.D. 1918. The pearly fresh-water mussels of Ontario. Contributions to Canadian Biology, Supplement to the 7th Annual Report, Sessional Paper No. 38, Fisheries Branch, Department of Naval Service:75-91.

Dyke, S., pers. comm. 2004. Email correspondence to J. Carney. November 2004. North Dakota Fish and Game. 500 Lafayette Road St. Paul, Minnesota. 55155-4040.

Ecological Specialists Inc. 1999. Final report: Unionid survey in the western basin of Lake Erie near the Bass Islands and southwest shore. Prepared for: Ohio Division of Wildlife - Department of Natural Resources, Columbus, Ohio and U.S. Fish and Wildlife Service, Reynoldsburg, Ohio. 22 pp.

Enns, A., pers. comm. 2016. Email correspondence to B. Bennett (COSEWIC member) forwarded to D.A.W. Lepitzki. 25 November. National Data Manager, NatureServe Canada.

Environment Canada. 2011. State of Lake Winnipeg: 1999-2007. viii + 209 pp.

Erickson, M., pers. comm. 2005. Email corresponded to J. Carney. November 2005. Manitoba Water Stewardship, Fisheries Branch. 200 Saulteaux Crescent, Winnipeg, Manitoba R3J 3W3

Esch, G.W., and J.C. Fernandez. 1993. A Functional Biology of Parasitism. Ecological and Evolutionary Implications. Chapman and Hall, London, United Kingdom. xiii + 337 pp.

Fisheries and Oceans Canada. 2016. Recovery strategy and action plan for the Mapleleaf (Quadrula quadrula) in Canada (Great Lakes-Western St. Lawrence population) [Proposed]. Species at Risk Act Recovery Strategy Series. Fisheries and Oceans Canada, Ottawa. vi + 57 pp.

Friesen, C., pers. comm. 2016. Email correspondence to B. Bennett (COSEWIC member) forwarded to D.A.W. Lepitzki. 25 November. Coordinator, Manitoba Conservation Data Centre.

Fuller, S.L.H. 1974. Clams and Mussels (Mollusca: Bivalvia). Pp. 215-273. In C.W. Hart, Jr. and S.L.H. Fuller (eds.). Pollution Ecology of Freshwater Invertebrates. Academic Press, New York, New York, U.S.A. xiv. + 389 pp.

Gagnon, E., pers. comm. 2005. Email correspondence to J. Metcalfe-Smith. November 2005. Environment Canada, Evaluation and Information Management. 351 St. Joseph Boulevard, Gatineau, Quebec.

Galbraith, H.S., D.T. Zanatta, and C.C. Wilson. 2015. Comparative analysis of riverscape genetic structure in rare, threatened and common freshwater mussels. Conservation Genetics 16:845-857.

Gatenby, C.M., R.J. Neves, and B.C. Parker. 1993. Preliminary observations from a study to culture recently metamorphosed mussels. Bulletin of the North American Benthological Society10:128 [abstract].

Gillis, P.L. 2012. Cumulative impacts of urban runoff and municipal wastewater effluents on wild freshwater mussels (Lasmigona costata). Science of the total Environment 431:348-356.

Gillis, P.L., S.K. Higgins, and M.B. Jorge. 2014. Evidence of oxidative stress in wild freshwater mussels (Lasmigona costata) exposed to urban-derived contaminants. Ecotoxicology and Environmental Safety 102:62-69.

Gillis, P.L., and G.L. Mackie. 1994. Impact of the Zebra Mussel, Dreissena polymorpha, on populations of Unionidae (Bivalvia) in Lake St. Clair. Canadian Journal of Zoology 72:1260-1271.

Gordon, M.J., B.K. Swan, and C.G. Patterson. 1978. Baeoctenus bicolor (Diptera: Chironomidae) parasitic in unionid bivalve molluscs, and notes on other chironomid-bivalve associations. Journal of the Fisheries Research Board of Canada35:154-157.

Graf, D.L., and D. Ó Foighil. 2000. The evolution of brooding characters among the freshwater pearly mussels (Bivalvia: Unionoidea) of North America. Journal of Molluscan Studies 66:157-170.

Graveline, P.G., W.J. Western, and D.S. MacDonell. 2005. Rat River - Joubert Creek aquatic habitat and riparian assessment survey. Unpublished report prepared for Seine Rat River Conservation District by North/South Consultants, Winnipeg, Manitoba 98 pp.

GRCA (Grand River Conservation Authority). 1997. State of the Grand River watershed: focus on watershed issues 1996-1997. Grand River Conservation Authority, Cambridge, Ontario. 36 pp.

GRCA (Grand River Conservation Authority). 1998. State of the watershed report: background report on the health of the Grand River watershed, 1996-97. Grand River Conservation Authority, Cambridge, Ontario. 143 pp.

GRCA (Grand River Conservation Authority). 2014. State of the watershed report: Spring 2014 a grand history in the making. Grand River Conservation Authority, Cambridge, Ontario. 12 pp.

Haag, W.R., D.J. Berg, D.W. Garton, and J.L. Farris. 1993. Reduced survival and fitness in native bivalves in response to fouling by the introduced Zebra Mussel (Dreissena polymorpha) in western Lake Erie. Canadian Journal of Fisheries and Aquatic Sciences 50:13-19.

Haag, W.R., and J.L. Staton. 2003. Variation in fecundity and other reproductive traits in freshwater mussels. Freshwater Biology 48:2118-2130.

Hanson, J.M., W.C. MacKay, and E.E. Prepas. 1989. Effect of size-selective predation by muskrats (Ondatra zebithicus) on a population of unionid clams (Anodonta grandis simpsonianus). Journal of Animal Ecology 58:5-28.

Hart, R.A. 1995. Mussel(Bivalvia: Unionidae) habitat suitability criteria for the Otter Tail River, Minnesota. M.S. Thesis, North Dakota State University. 60+ pp.

Hay, R., D. Heath, and L. Kitchel. 2003. Freshwater Mussels of the Upper Mississippi River. Wisconsin Department of Natural Resources. 60 pp.

Hendrix, S.S., M.F. Vidrine, and R.H. Hartenstine. 1985. A list of records of freshwater aspidogastrids (Trematoda) and their hosts in North America. Proceedings of the Helminthological Society of Washington 52:289-296.

Howard, A.D., and B.J. Anson. 1922. Phases in the parasitism of the Unionidae. Journal of Parasitology 9:68-82.

Imlay, M.J., and M.L. Paige. 1972. Laboratory growth of freshwater sponges, unionid mussels, and sphaeriid clams. Progressive Fish-Culturist34:210-216.

IUCN Species Survival Commission. 2016. IUCN redlist entry for Quadrula quadrula. Web site: http://www.iucnredlist.org/ [accessed August 2016].

Johnson, R.L., F.Q. Liang, and J.L. Farris. 1998a. Genetic diversity among four Amblemini species (Bivalvia: Unionidae) in the Cache and White Rivers, Arkansas. Southwestern Naturalist 43:321-332.

Johnson, R.L., F.Q. Liang, and J.L. Farris. 1998b. Genetic relationships of several Amblemini species (Bivalvia: Unionidae) in Arkansas. Journal of Shellfish Research 17:1237-1242.

Johnson, R.L., F.Q. Liang, and J.L. Farris. 1998c. Genetic diversity and celluloytic activity among several species of unionid bivalves in Arkansas. Journal of Shellfish Research 17:1375-1382.

Jones, G., and N. Armstrong. 2001. Long-term trends in total nitrogen and total phosphorus concentrations in Manitoba streams. Water Quality Management Section, Water Branch. Manitoba Conservation Branch Report No. 2001 - 07. 154 pp.

Kidd, B.T. 1973. Unionidae of the Grand River drainage, Ontario, Canada. M.Sc. dissertation, Carleton University, Ottawa, Ontario, Canada. 172 pp.

Lake Winnipeg Implementation Committee. 2005. Restoring the Health of Lake Winnipeg - A Report by the Lake Winnipeg Implementation Committee. 56 pp.

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, Jr. 1980. Atlas of North American Freshwater Fishes. North Carolina Biological Survey Publication 1980-12. North Carolina State Museum of Natural History, Raleigh, North Carolina, U.S.A. ix + 854 pp.

Levine, T., pers. comm. 2004. Email correspondence to J. Metcalfe-Smith. November 2004. Ph.D. Candidate, Department of Zoology, Miami University, 212 Pearson Hall, Oxford, Ohio 45056.

Libois, R.M., and C. Hallet-Libois. 1987. The unionid mussels (Mollusca: Bivalvia) of the Belgian upper River Meuse: an assessment of the impact of hydraulic works on the water self-purification. Biological Conservation 42:115-132.

LTVCA (Lower Thames Valley Conservation Authority). 2012. Lower Thames Valley Watershed Report Card 2012. Lower Thames Valley Conservation Authority, Chatham, Ontario. 8 pp.

Lucy, F., L.E. Burlakova, A. Karatayev, S. Mastitsky, and D.T. Zanatta. 2014. Zebra mussel impacts on unionids: A synthesis of trends in North America and Europe. Pp. 623-646. In T.F. Nalepa and D.W. Schloesser (eds.). Quagga and Zebra Mussels: Biology, Impact, and Control, 2nd Edition, CRC Press, Boca Raton Florida.

Lydeard, C., M. Mulvey, and G.M. Davis. 1996. Molecular systematics and evolution of reproductive traits of North American freshwater unionacean mussels (Mollusca: Bivalvia) as inferred from 16S rRNA gene sequences. Philosophical Transactions of the Royal Society London B 351:1593-1603.

Mackie, G.L., and J.M. Topping. 1998. Historical changes in the Unionid fauna of the Sydenham River watershed and downstream changes in shell morphometrics of three common species. Canadian Field-Naturalist 102:617-626.

Manitoba Conservation. 2000. Development of a Nutrient Management Strategy for Surface Waters in Southern Manitoba. Water Quality Management Section, Manitoba Conservation, Winnipeg, Manitoba. Information Bulletin 2000-2E. 10 pp.

Maskant, K. 2004. Zebra Mussels found in the Thames. Thames Strategy Newsletter. Winter 2003-2004:2.

Master, L., D. Faber-Langendoen, R. Bittman, G.A. Hammerson, B. Heidel, J. Nichols, L. Ramsay, and A. Tomaino. 2009. NatureServe conservation status assessments: factors for assessing extinction risk. NatureServe, Arlington, Virginia. 57 pp.

Mazur, K. 2007. Assiniboine River bridge construction. PTH 10 - 18th Street Brandon. Mussel survey and relocation. A report prepared for Manitoba Infrastructure and Transportation by North/South Consultants Inc. 7 pp.

McGoldrick D.J., J.L. Metcalfe-Smith, M.T. Arts, D.W. Schloesser, T.J. Newton, G.L. Mackie, E.M. Monroe, J. Biberhofer, K. Johnson. 2009. Characteristics of a refuge for native freshwater mussels (Bivalvia: Unionidae) in Lake St. Clair. Journal of Great Lakes Research 35:137-146.

McNichols-O’Rourke, K.A., A. Robinson, and T.J. Morris. 2012. Summary of freshwater mussel timed search surveys in southwestern Ontario in 2010 and 2011. Canadian Manuscript Reports of Fisheries and Aquatic Sciences. 3009:vi + 42 p.

Meffe, G.K., and C.R. Carroll. 1997. Principles of Conservation Biology, 2nd ed. Sinauer Associates Inc. Sunderland Massachusetts, U.S.A. 729 pp.

Metcalfe-Smith, J.L., J. Di Maio, S.K. Staton, and S.R. de Solla. 2003. Status of the freshwater mussel communities of the Sydenham River, Ontario, Canada. American Midland Naturalist 150:37-50.

Metcalfe-Smith, J.L., J. Di Maio, S.K. Staton, and G.L. Mackie. 2000a. Effect of sampling effort on the efficiency of the timed search method for sampling freshwater mussel communities. Journal of the North American Benthological Society 19(4):725-732.

Metcalfe-Smith, J.L., G.L. Mackie, J. Di Maio, and S.K. Staton. 2000b. Changes over time in the diversity and distribution of freshwater mussels (Unionidae) in the Grand River, southwestern Ontario. Journal of Great Lakes Research 26(4):445-459.

Metcalfe-Smith, J.L., D.J. McGoldrick, M. Williams, D.W. Schloesser, J. Biberhofer, G.L. Mackie, M.T. Arts, D.T. Zanatta, K. Johnson, P. Marangelo, and T.D. Spencer. 2004. Status of a refuge for native freshwater mussels (Unionidae) from impacts of the exotic Zebra Mussel (Dreissena polymorpha) in the delta area of Lake St. Clair. Environment Canada, National Water Research Institute, Burlington, Ontario. NWRI Technical Note No. AEI-TN-04-001. 50 pp.

Metcalfe-Smith, J.L., S.K. Staton, G.L. Mackie, and N.M. Lane. 1998a. Selection of candidate species of freshwater mussels (Bivalvia: Unionidae) to be considered for national status designation by COSEWIC. Canadian Field-Naturalist 112:425-440.

Metcalfe-Smith, J.L., S.K. Staton, G.L. Mackie, and I.M. Scott. 1999. Range, population stability and environmental requirements of rare species of freshwater mussels in southern Ontario. Environment Canada, National Water Research Institute, Burlington, Ontario. NWRI Contribution Bo. 99-058. 91 pp.

Metcalfe-Smith, J.L., S.K. Staton, G.L. Mackie, and E.L. West. 1998b. Assessment of the current conservation status of rare species of freshwater mussels in southern Ontario. Environment Canada, National Water Research Institute, Burlington, Ontario. NWRI Contribution No. 98-019. 84 pp.

Metcalfe-Smith, J.L., and D.T. Zanatta. 2003. Development of a monitoring program for tracking the recovery of endangered freshwater mussels in the Sydenham River, Ontario: Report on activities in Year 1 (2002-03). Environment Canada, National Water Research Institute, Burlington, Ontario. NWRI Technical Note No. AEI-TN-03-001. 48 pp.

Michelson, E.H. 1970. Aspidogaster conchicola from freshwater gastropods in the United States. Journal of Parasitology 56:709-712.

Minke-Martin, V., K.A. McNichols-O’Rourke, and T.J. Morris. 2015. Initial application of the half-hectare unionid survey method in wetland habitats of the Laurentian Great Lakes, southern Ontario. Canadian Manuscript Reports of Fisheries and Aquatic Sciences. 3069:vi + 35 p.

Miura, T., and T. Yamashiro. 1990. Size selective feeding of Anodonta calipygos, a phytoplanktivorous freshwater bivalve, and viability of egested algae. Japanese Journal of Limnology 51:73-78.

Morris, T.J. 1996. The unionid fauna of the Thames River drainage, southwestern Ontario. Prepared for Aquatic Ecosystems Branch, Ontario Ministry of Natural Resources. 59 pp.

Morris, T.J., pers. comm. 2015. Email correspondence to D. Zanatta. August 2015. Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences, 867 Lakeshore Rd., Burlington Ontario L7S 1A1.

Morris, T.J., and J. Di Maio. 1998-1999. Current distributions of freshwater mussels (Bivalvia: Unionidae) in rivers of southwestern Ontario. Malacological Review 31/32:9-17.

Morris, T.J., and A. Edwards. 2007. Freshwater mussel communities of the Thames River, Ontario: 2004-2005. Canadian Manuscript Reports of Fisheries and Aquatic Sciences. 2810:v + 30 pp.

Morris, T. J., K.A. McNichols-O’Rourke, and A. Robinson. 2012a. A preliminary survey of the freshwater mussels of the Welland River watershed in 2008. Canadian Manuscript Reports of Fisheries and Aquatic Sciences. 2991:iv + 11 p.

Morris, T. J., K.A. McNichols-O’Rourke, and A. Robinson. 2012b. A preliminary survey of the freshwater mussels of the Bayfield River watershed and nearby Lake Huron tributaries. Canadian Manuscript Reports of Fisheries And Aquatic Sciences. 2993:v + 22 p.

Mummert, A.K., R.J. Neves, T.J. Newcomb, and D.S. Cherry. 2003. Sensitivity of juvenile freshwater mussels (Lampsilis fasciola, Villosa iris) to total and un-ionized ammonia. Environmental Toxicology and Chemistry 22:2545-2553.

Nakato, T., J. Christensen, and L.A. Carver. 2005. Size and age distributions of freshwater mussels consumed by muskrats in the Mississippi River near Fairport, Iowa. Poster Presentation. Freshwater Mollusk Conservation Society 4th Biennial Symposium. May 15-18, 2005. St. Paul, Minnesota.

Nalepa, T.F., D.J. Hartson, G.W. Gostenik, D.L. Fanslow, and G.A. Lang. 1996. Changes in the freshwater mussel community of Lake St. Clair from Unionidae to Dreissena polymorpha in eight years. Journal of Great Lakes Research 22(2):354-369.

NatureServe. 2016. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Web site: http://explorer.natureserve.org [accessed: 19 May 2016].

Neel, J.K. 1941. A taxonomic study of Quadrula quadrula (Rafinesque). Occasional Papers of the Museum of Zoology, University of Michigan 448:1-8, 1 plate.

Nelson, M., M. Veliz, S. Staton, and E. Dolmage. 2003. Towards a recovery strategy for Species at Risk in the Ausable River: Synthesis of background information. Prepared for the Ausable River Recovery Team. 92 pp.

Neves, R.J., and S.N. Moyer. 1988. Evaluation of techniques for age determination of freshwater mussels (Unionidae). American Malacological Bulletin 6:179-188.

Neves, R.J., and M.C. Odum. 1989. Muskrat predation on endangered freshwater mussels in Virginia. Journal of Wildlife Management53:934-941.

Nichols, S.J., and D. Garling. 2000. Food-web dynamics and trophic-level interactions in a multispecies community of freshwater unionids. Canadian Journal of Zoology 78:871-882.

Nichols, S.J., and D.A. Wilcox. 1997. Burrowing saves Lake Erie clams. Nature 389:921.

NPCA (Niagara Peninsula Conservation Authority). 2012. Watershed Report Cards. Web site: https://npca.ca/watershed-report-cards [accessed October 2015].

Oliver, J., and M. Lowdon. 2015. Bradbury River Mussel Salvage. A report prepared for East Side Road Authority (ESRA). AAE Tech Services Inc. 11 pp.

Owen, B. 2015. Tracking invasion of zebra mussels. Winnipeg Free Press . Web site: http://www.winnipegfreepress.com/local/tracking-invasion-of-zebra-mussels-313146631.html [accessed August 2015].

Parmalee, P.W., and A.E. Bogan. 1998. The Freshwater Mussels of Tennessee. The University of Tennessee Press, Knoxville, Tennessee. xi + 328 pp.

Paterson, W.L., T.A. Griffith, L.E. Burlakova, R.W. Krebs, and D.T. Zanatta. 2015. An evaluation of the genetic structure of mapleleaf mussels (Quadrula quadrula) in the Lake Erie watershed. Journal of Great Lakes Research 41:1123-1130.

Pip, E. 2000. The decline of freshwater mollusks in southern Manitoba. Canadian Field-Naturalist 114:555-560.

Pip, E., pers. comm. 2004. Email correspondence to J. Carney. May 2004. Department of Biology, University of Winnipeg. 515 Portage Ave. Winnipeg, MB R3B 2E9.

Poos, M., A. Dextrase, A. Schwalb, and J. Ackerman. 2010. Secondary invasion of the Round Goby into high diversity Great Lakes tributaries and species at risk hotspots: potential new concerns for endangered freshwater species. Biological Invasions 12:1269-1284.

Raikow, D.F., and S.K. Hamilton. 2001. Bivalve diets in a midwestern U.S. stream: a stable isotope enrichment study. Limnology and Oceanography 46:514-522.

Reid, S.M., A. Brumpton, S. Hogg, and T. Morris. 2014. A comparison of visual-tactile and clam rake search methods to survey freshwater mussels in Great Lakes coastal wetlands. Walkerana - The Journal of the Freshwater Mollusk Conservation Society 17:17-23.

Reid, S.M., V. Kopf, A. LeBaron, T.J. Morris. 2016. Remnant freshwater mussel diversity in Rondeau Bay, Lake Erie. Canadian Field-Naturalist 130:76-81.

Richards, R.P. 1990. Measures of flow variability and a new flow-based classification of Great Lakes tributaries. Journal of Great Lakes Research 16:53-70.

Scaife, B., and L. Janusz. 1992. A survey of freshwater mussels on the Assiniboine River, September 1992. Manitoba Department of Natural Resources Fisheries Branch Manuscript Report No. 92-02. v + 24 p.

Schloesser, D.W., W.P. Kovalak, G.D. Longdon, K.L. Ohnesorg, and R.D. Smithee. 1998. Impact of zebra and quagga mussels (Dreissena spp.) on freshwater unionids (Bivalvia: Unionidae) in the Detroit River of the Great Lakes. The American Midland Naturalist 140:299-313.

Schloesser, D.W., J.L. Metcalfe-Smith, W.P. Kovalak, G.D. Longton, and R.D. Smithee. 2006. Extirpation of freshwater mussels (Bivalvia: Unionidae) following the invasion of dreissenid mussels in an interconnecting river of the Laurentian Great Lakes. American Midland Naturalist 155:307-320.

Schloesser, D.W., and T.F.Nalepa. 1994. Dramatic decline of unionid bivalves in offshore waters of western Lake Erie after infestation by the Zebra Mussel, Dreissena polymorpha. Canadian Journal of Fisheries and Aquatic Sciences 51:2234-2242.

Schloesser, D.W., T.F. Nalepa, and G.W. Mackie. 1996. Zebra Mussel infestation of unionid bivalves in North America. American Zoologist 36:300-310.

Schneider, K., pers. comm. 2002. Email correspondence to J. Metcalfe-Smith. November 2002. Stuyvesant Environmental Consulting, LLC. P.O. Box 169, 16 Frisbee Lane, Syuyvesant Falls, New York 12174.

Schwalb, A.N., and M.T. Pusch. 2007. Horizontal and vertical movements of unionid mussels in a lowland river. Journal of the North American Benthological Society, 26:261-272.

Schwebach, M., D. Schriever, V. Kanodia, N. Dillon, M. Hove, M. McGill, C. Nelson, J. Thomas, and A. Kapuscinski. 2002. Channel Catfish is a suitable host for Mapleleaf glochidia. Ellipsaria 4:12-13.

Scott, W.B., and E.J. Crossman. 1973. Freshwater Fishes of Canada. Bulletin 184. Fisheries Research Board of Canada, Ottawa, Canada. xi + 966 pp.

SCRCA (St. Clair Region Conservation Authority). 2013. Watershed Report Cards. Web site: http://www.scrca.on.ca/about-us/2013-watershed-report-cards/. [accessed October 2015].

Sietman, B.E., J.M. Davis, and M.C. Hove. 2012. Mantle display and glochidia release behaviors of five quadruline freshwater mussel species (Bivalvia: Unionidae). American Malacogical Bulletin 30(1):39-46.

Silverman, H., S.J. Nichols, J.S. Cherry, E. Achberger, J.W. Lynn, and T.H. Dietz. 1997. Clearance of laboratory-cultured bacteria by freshwater bivalves: differences between lentic and lotic unionids. Canadian Journal of Zoology 75:1857-1866.

Snell and Cecile Environmental Research. 1995. Ausable Bayfield Conservation Authority Watershed Management Strategy. Ausable Bayfield Conservation Authority, Exeter, Ontario. 54 pp + appendices.

Spooner, D.E., M.A. Xenopoulos, C. Schneider, and D.A. Woolnough. 2011. Coextirpation of host-affiliate relationships in rivers: the role of climate change, water withdrawal, and host-specificity. Global Change Biology 17:1720-1732.

Staton, S., pers. comm. 2005. Email correspondence to J. Metcalfe-Smith. October 2005. Great Lakes Laboratory for Fisheries and Aquatic Sciences. 87 Lakeshore Rd., Burlington, Ontario L7R 4A6.

Staton, S.K., A. Dextrase, J.L. Metcalfe-Smith, J. Di Maio, M. Nelson, J. Parish, B. Kilgour, and E. Holm. 2003. Status and trends of Ontario’s Sydenham River ecosystem in relation to aquatic species at risk. Environmental Monitoring and Assessment 88:283-310.

Stewart, K.W., and D.A. Watkinson. 2004. The Freshwater Fishes of Manitoba. University of Manitoba Press, Winnipeg, Manitoba, Canada. 276 pp.

Strayer, D.L., and A.R. Fetterman. 1999. Changes in the distribution of freshwater mussels (Unionidae) in the upper Susquehanna River basin, 1955-1965 to 1996-1997. American Midland Naturalist 142:328-339.

Strayer, D.L., and D.R. Smith. 2003. A guide to sampling freshwater mussel populations. American Fisheries Society, Monograph 8, Bethesda, Maryland. 103 pp.

Sydenham River Recovery Team. 2002. Recovery Strategy for Aquatic Species at Risk in the Sydenham River: An Ecosystem Approach. St. Clair Region Conservation Authority 78 pp. Web site: http://www.sydenhamriver.on.ca/Publications/RecoveryStrategyJuly2002.pdf [accessed October 2015].

Tankersley, R.A. 1996. Multipurpose gills: effect of larval brooding on the feeding physiology of freshwater unionid mussels. Invertebrate Biology 115: 243-255.

Taylor, I., B. Cudmore-Vokey, C. MacCrimmon, S. Madzia, and S. Hohn. 2004. The Thames River Watershed: Synthesis Report (draft). Prepared for the Thames River Recovery Team. 74 pp.

Thames River Background Study Research Team. 1998. The Thames River Watershed: A background study for nomination under the Canadian Heritage Rivers System. Upper Thames River Conservation Authority, London, Ontario. 162 pp.

Thames River Recovery Team. 2004. Recovery strategy for species at risk in the Ausable River: An ecosystem approach. Upper Thames River Consevation Authority. 99 pp. Web site: http://thamesriver.on.ca/watershed-health/aquatic-species-at-risk/ [accessed October 2015]

Therriault, T.W., A.M. Weise, S.N. Higgins, S. Guo, and J. Duhaime. 2013. Risk Assessment for Three Dreissenid Mussels (Dreissena polymorpha, Dreissena rostriformis bugensis, and Mytilopsis leucophaeata) in Canadian Freshwater Ecosystems. DFO Canadian Science Advisory Secretariat Research Document 2012/174:v + 88 p.

Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. 2nd edition. American Fisheries Society, Special Publication 26, Bethesda, Maryland, U.S.A. ix + 526 pp.

Tyrrell, M., and D.J. Hornbach. 1998. Selective predation by muskrats on freshwater mussels in 2 Minnesota rivers. Journal of the North American Benthological Society 17:301-310.

U.S.E.P.A. (United States Environmental Protection Agency). 2013. Aquatic life ambient water quality criteria for ammonia - freshwater. 242 pp.

UTRCA (Upper Thames River Conservation Authority). 2012. Upper Thames River Watershed Report Card Summary. Upper Thames River Conservation Authority, London, Ontario. 4 pp.

Vandean, T. 2003. The negative social impacts of Manitoba’s hog industry and the implications for social sustainability. Research Report for Manitoba Legislative Internship Programme. 36 pp.

Vidrine, M.F. 1996. North American Najadicola and Unionicola: Systematics and Coevolution. Gail Q. Vidrine Collectibles, Eunice, Louisiana, U.S.A. vi + 145 pp.

Ward, J.E. 1996. Biodynamics of suspension-feeding in adult bivalve mussels: particle capture, processing, and fate. Invertebrate Biology 115:218-231.

Ward, J.M., and A. Ricciardi. 2013. Impacts of Dreissena on benthic macroinvertebrate 1731 communities: predictable patterns revealed by invasion history. Pp. 599-610. In T.F. Nalepa and D. Schloesser (eds.). Quagga and Zebra Mussels: Biology, Impacts, and Control, CRC Press, Florida.

Watershed Checkup. 2015. Ontario Conservation Authority Watershed Report Cards. Web site: http://watershedcheckup.ca/conservation-authority-map [accessed October 2015].

Watkinson, D., pers. comm. 2015. Email correspondence to T. Morris. August 2015. Freshwater Institute 501 University Crescent, Winnipeg, Manitoba, R3T 2N6.

Watson, E.T., pers. comm. 2015. Email correspondence to J. Carney. August 2015. Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, R3T 2N6

Watson, E.T., L.C. Graham, and W.G. Franzin. 1998. The distribution of Unionidae (Mollusca: Bivalvia) in the Assiniboine River drainage in Manitoba. Canadian Technical Report of Fisheries and Aquatic Sciences 2232: iv + 31 p.

Watters, G.T. 1999. Freshwater mussels and water quality: A review of the effects of hydrologic and instream habitat alterations. Proceedings of the First Freshwater Mollusk Conservation Society Symposium. Ohio Biological Survey, Columbus Ohio. Pp. 261-274

Wendel, J.L., and S.W. Kelsch. 1999. Summer range and movement of Channel Catfish in the Red River of the North. American Fisheries Society Symposium 24:203-214.

Williams, C.O. 1942. Observations on the life history and taxonomic relationships of the trematode Aspidogaster conchicola. Journal of Parasitology 28:467-475.

Williams, J.D., M.L. Warren, K.S. Cummings, J.L. Harris, and R.J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18:6-22.

Yeager, M.M., and D.S. Cherry. 1994. Feeding and burrowing behaviors of juvenile rainbow mussels, Villosa iris (Bivalvia: Unionidae). Journal of the North American Benthological Society 13:217-222.

Yeager, M.M., D.S. Cherry, and R. Neves. 1993. Interstitial feeding behavior of juvenile unionid mussels. Association of Southeastern Biologists Bulletin40: 113 [abstract].

Zanatta, D.T. 2000. Biotic and abiotic factors related to the distribution of unionid mussels in Lake St. Clair. M.Sc. Thesis. University of Guelph. Guelph, Ontario. 121 pp.

Zanatta, D.T., J. Bossenbroek, L. Burlakova, T. Crail, F. de Szalay, T.A. Griffith, D. Kapusinski, A. Karateyev, R.A. Krebs, E.S. Meyer, W.L. Paterson, T.J. Prescott, M.T. Rowe, D. Schloesser, and M.C. Walsh. 2015. Distribution of native mussel (Unionidae) assemblages in coastal Lake Erie, Lake St. Clair, and connecting channels, twenty-five years after the dreissenid invasion. Northeastern Naturalist 22:223-235.

Zanatta, D.T., G.L. Mackie, J.L. Metcalfe-Smith, and D.A. Woolnough. 2002. A refuge for native freshwater mussels (Bivalvia: Unionidae) from impacts of the exotic Zebra Mussel (Dreissena polymorpha) in Lake St. Clair. Journal of Great Lakes Research 28:479-489.

Biographical summary of report writers

Dr. David Zanatta is an Associate Professor in the Biology Department at Central Michigan University. Dr. Zanatta has over 15 years of experience working on unionid mussels. He has a B.Sc. (Hons.) in Biology from Laurentian University (1998); an M.Sc. in Zoology from the University of Guelph (2000); a Ph.D. from the University of Toronto (2007) where he researched the evolution and population genetics of lampsiline mussels; and held an NSERC post-doctoral fellowship at Trent University in 2008 prior to starting a professorship at Central Michigan University. Dr. Zanatta has authored or co-authored numerous peer-reviewed papers on freshwater mussel biology, including research on the Mapleleaf mussel. He has also written several COSEWIC status reports on Canadian freshwater mussel species and is a member of the Molluscs Specialist Subcommittee of COSEWIC. Dr. Zanatta is a member of the recovery teams for the Thames, Sydenham, and Ausable rivers as well as the Ontario Freshwater Mussel Recovery Team.

Jordan Hoffman is a graduate student in Biology at Central Michigan University. He received his BS from Oakland University (Rochester, Michigan) in 2011 and an MS in Ecology and Evolutionary Biology from Tulane University (New Orleans, Louisiana) in 2014. Jordan has diverse interests in biodiversity and conservation biology and has recently completed his MS Thesis investigating dispersal and genetic structure in Ontario populations of Quadrula quadrula. He is a member of the Freshwater Mollusk Conservation Society.

Dr. Joseph Carney is an associate professor at Lakehead University, Thunder Bay, Ontario. He received his Ph.D. from the University of Manitoba in 2000 investigating the evolution and community ecology of parasites of yellow perch (Perca flavescens). Since 2002 he has initiated a research program investigating the ecology and conservation of freshwater mussels (Mollusca: Unionidae) within the Red River drainage in Manitoba, Saskatchewan, and North Dakota. He has published several scientific papers and reports focusing on freshwater mussels. He is a member of the American Society of Parasitologists, Canadian Society of Zoology, and the Freshwater Mollusk Conservation Society. He has been a member of the COSEWIC Molluscs SSC since 2005 and is the current co-chair (beginning in 2015).

Collections examined

Collections of freshwater mussels from Manitoba are limited. The Manitoba Museum of Man and Nature has a small collection deposited by Ernie Watson. This has been examined by William Watkins, one of the writers of the previous report. A larger research collection is maintained by J. Carney, report co-writer, and this collection is regularly examined. Vouchered specimens from the personal collection maintained by Dr. Eva Pip have been examined.

In 1996, all available historical and recent data on the occurrences of freshwater mussel species throughout the lower Great Lakes drainage basin were compiled into a computerized, GIS-linked database referred to as the Lower Great Lakes Unionid Database. The database is housed at the Fisheries and Oceans Canada offices in Burlington, Ontario. Data sources included the primary literature, natural history museums, federal, provincial, and municipal government agencies (and some American agencies), conservation authorities, Remedial Action Plans for the Great Lakes Areas of Concern, university theses, and environmental consulting firms. Mussel collections held by six natural history museums in the Great Lakes region (Canadian Museum of Nature, Ohio State University Museum of Zoology, Royal Ontario Museum, University of Michigan Museum of Zoology, Rochester Museum and Science Center, and Buffalo Museum of Science) were the primary sources of information, accounting for over two-thirds of the data acquired. J.L. Metcalfe-Smith (co-writer of the 2006 status report) personally examined the collections held by the Royal Ontario Museum, University of Michigan Museum of Zoology, and Buffalo Museum of Science, as well as smaller collections held by the Ontario Ministry of Natural Resources. The database continues to be updated and contains over 10,000 records of unionids from Lake Ontario, Lake Erie, Lake St. Clair, and their drainage basins as well as several of the major tributaries to lower Lake Huron. The databased is currently managed by Fisheries and Oceans Canada, Great Lakes Laboratory for Fisheries and Aquatic Sciences.