Striped bass (Morone saxatilis) COSEWIC assessment and status report: chapter 11

Technical Summary

Morone saxatilis

Striped bass - Bar rayé

Southern Gulf of St. Lawrence Population

A population spawning in the northwest Miramichi River.

Range of Occurrence in Canada:
Southern Gulf of St. Lawrence (particularly the east coast of New Brunswick, but also Prince Edward Island and part of the coast of Nova Scotia).

Extent and Area information

Extent of occurrence (EO) : (km²)
(Estimated from the southern Gulf of St. Lawrence population shown in Figure 2) 93,000 km²
Specify trend (decline, stable, increasing, unknown):
Stable
Are there extreme fluctuations in EO (> 1 order of magnitude)?
No
Area of occupancy (AO) (km²)(Based on spawning habitat):
<100 km²
Specify trend (decline, stable, increasing, unknown):
Stable
Are there extreme fluctuations in AO (> 1 order magnitude)?
No
Number of extant locations:
A single spawning ground, in the NW Miramichi River.
Specify trend in # locations (decline, stable, increasing, unknown):
Stable
Are there extreme fluctuations in # locations (>1 order of magnitude)?
No
Habitat trend (specify declining, stable, increasing or unknown trend in area, extent or quality of habitat):
Appears stable.

Population information

Generation time (average age of parents in the population):
12 years.
Number of mature individuals:
50,000 (1995);
< 4,000 (1998-2000);
29,000 (2002).
Total population trend:
Declining from 1995 to 2000, increasing in 2001 and 2002.
If decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period):
93% decrease from 1995 to 1998 (50,000 to 3,400), then 853% increase from 1998 to 2002 (3,400 to 29,000).
Are there extreme fluctuations in number of mature
individuals (> 1 order of magnitude)?
Yes
Is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., ≤ 1 successful migrant / year)?
No. The population is fragmented among several rivers to overwinter, but all spawners congregate on the same spawning grounds.
List each population and the number of mature individuals in each:
A single population. See figures above.
Specify trend in number of populations (decline, stable, increasing, unknown):
Stable
Are there extreme fluctuations in number of populations (>1 order of magnitude)?
No

Threats (actual or imminent threats to populations or habitats)

  • Heavy exploitation: it appears that this factor is in the process of being controlled; the commercial, sport and ceremonial (First Nations) fisheries were limited, and subsequently closed, when the estimate of the number of spawners on the spawning ground fell below a predetermined threshold of 5,000 spawners. Numbers began to increase starting in 2001. Mortality of juveniles caught as bycatch in gear intended for other species still occurs (smelt, eel). Finally, the confinement of bass in the estuaries of several rivers where they overwinter could increase the risks of poaching and exposure to other mortality factors.
  • Habitat changes: indeterminate risk associated with the presence of industrial and municipal effluent near spawning and nursery habitats. However, there is no evidence of mortality due to this factor in recent years.

Rescue Effect (immigration from an outside source)

Very unlikely. Mark-recapture data indicate very little contact with populations to the south.

Does species exist elsewhere (in Canada or outside)?
Yes
Status of the outside population(s)?
In the west, the St. Lawrence population is extirpated. In the south, two of three Bay of Fundy populations have disappeared. The third (Shubenacadie) is extant but appears to be found primarily in Minas Basin. Further south, several U.S. populations are abundant but do not appear to migrate further north than the Bay of Fundy.
Is immigration known or possible?
Very unlikely.
Would immigrants be adapted to survive here?
Yes?
Is there sufficient habitat for immigrants here?
Yes?

Quantitative Analysis

Not available

Current Status:

NatureServe Ranks (NatureServe 2004)

Global Status:
G5
National Status:
CanadaN3?; USAN5
Provincial / State Status:
Canada: NB (S2), NS (S1), PE (S2N), QC (SX).
USA (selected states):
Connecticut (S3), Delaware (S5), Maine (S5), Maryland (S5), Massachusetts (SU), New Hampshire (S4), New Jersey (S4), New York (S4), Rhode Island (SNR), Virginia (S4)

Status and Reasons for Designation

Status:
Threatened
Alpha-numeric code:
Met criteria for Endangered, B2ac(iv), but designated as Threatened, B2ac(iv); D2, because of the high degree of resilience evident in recent spawner abundance estimates.
Reasons for Designation:
This fish was once commercially important and is still highly prized by anglers. Threats include bycatch in various fisheries such as gaspereau, and rainbow smelt. Illegal take, particularly during ice fishing, is also believed to be a threat.

Applicability of Criteria

Criterion A (Declining Total Population): The thresholds are not met.

Criterion B (Small Distribution, and Decline or Fluctuation): It meets the threshold for Endangered B2ac(iv), in terms of area of occupancy, small number of locations, and extreme fluctuations in number of mature individuals.

Criterion C (Small Total Population Size and Decline): The thresholds are not met.

Criterion D (Very Small Population or Restricted Distribution): Qualifies as Threatened under D2 because it is only known from only one spawning location.

Criterion E (Quantitative Analysis): Data are not available.

St. Lawrence Estuary Population

Range of occurrence in Canada:
Quebec, St. Lawrence River and Estuary, from Lake Saint- Pierre to the Kamouraska area.

Extent and Area information

Extent of occurrence (EO) (km²)(Estimated from Figure 2):
Formerly <3000km²
Specify trend (decline, stable, increasing, unknown):
Not applicable
Are there extreme fluctuations in EO (>1 order of magnitude)?
No
Area of occupancy (AO) (km²):
Unknown
Specify trend (decline, stable, increasing, unknown):
Not applicable
Are there extreme fluctuations in AO (>1 order magnitude)?
No
Number of extant locations:
None
Specify trend in # locations (decline, stable, increasing, unknown):
Not applicable
Are there extreme fluctuations in # locations (>1 order of magnitude)?
No
Habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat:
Not applicable

Population information

Generation time (average age of parents in the population):
12 years
Number of mature individuals:
Nil
Total population trend:
Based on commercial catches from 1920 to 1965, presence highly variable. Significant decline in the 1950s and extirpation in the 1960s.
If decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period):
Not applicable
Are there extreme fluctuations in number of mature individuals (>1 order of magnitude)?
Not applicable
Is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., ≤ 1 successful migrant / year)?
Not applicable
List each population and the number of mature individuals in each:
Nil
Specify trend in number of populations (decline, stable, increasing, unknown):
Not applicable
Are there extreme fluctuations in number of populations (>1 order of magnitude)?
No

Threats (actual or imminent threats to populations or habitats)

  • Heavy exploitation: all data and observations on the issue are consistent. The commercial and sport fisheries were very intense and the regulations were not respected.
  • Habitat alterations: the disposal of dredge material in a section of the seaway is believed to have contributed to confining immature bass to a limited area along the south shore where fishing subsequently became concentrated.

Rescue Effect (immigration from an outside source)

Unknown

Does species exist elsewhere (in Canada or outside)?
Yes
Status of the outside population(s)?
In the east, one population in the Southern Gulf (Miramichi River). In the south, two of three Bay of Fundy populations have disappeared. The third (Shubenacadie) is extant but appears to be found primarily in Minas Basin. Further south, several U.S. populations are abundant but do not appear to migrate further north than the Bay of Fundy.
Is immigration known or possible?
Very unlikely
Would immigrants be adapted to survive here?
Yes?
Is there sufficient habitat for immigrants here?
Yes?

Quantitative Analysis

Not available

Current Status

NatureServe Ranks (NatureServe 2004)

Global Status:
G5
National Status:
CanadaN3?; USAN5
Provincial / State Status: 
Canada: NB (S2), NS (S1), PE (S2N), QC (SX
USA (selected states):
Connecticut (S3), Delaware (S5), Maine (S5), Maryland (S5), Massachusetts (SU), New Hampshire (S4), New Jersey (S4), New York (S4), Rhode Island (SNR), Virginia (S4)

Status and Reasons for Designation

Status:
Extirpated
Alpha-numeric code:
Not applicable
Reasons for Designation
The population from the St. Lawrence Estuary has disappeared as a consequence of illegal fishing, with the last record dating from 1968.

Applicability of Criteria

Criterion A (Declining Total Population): Not applicable.

Criterion B (Small Distribution, and Decline or Fluctuation): Not applicable.

Criterion C (Small Total Population Size and Decline): Not applicable.

Criterion D (Very Small Population or Restricted Distribution): Not applicable

Criterion E (Quantitative Analysis): Not applicable.

Bay of Fundy Population

Three populations spawning in the Saint John (N.B.), Annapolis and Shubenacadie (N.S.) rivers.

Range of occurrence in Canada:
For the existing population: Nova Scotia, Minas Basin and Shubenacadie-Stewiacke system. Range of occurrence undetermined for the two populations that have disappeared. It was probably limited to the interior Bay of Fundy.

Extent and Area information

Extent of occurrence (EO) (km²) (estimated from Figure 2):
29,000 km²
Specify trend (decline, stable, increasing, unknown):
Current trend unknown: No indication that it is currently declining, but it has declined in recent decades with the disappearance of two of the three populations. The freshwater habitats and estuaries of the Annapolis and Saint John rivers are no longer used by their respective bass populations. The areas used in the Bay of Fundy in summer have also likely decreased, but this is impossible to assess.
Are there extreme fluctuations in EO (>1 order of magnitude)?
No evidence of extreme fluctuations in EO, apart from changes indicated above.
Area of occupancy (AO) (km²) (based on spawning habitat)
<100 km²
Specify trend (decline, stable, increasing, unknown):
Two of three spawning areas have been lost.
Are there extreme fluctuations in AO (>1 order magnitude)?
No evidence of extreme fluctuations.
Number of extant locations:
1
Specify trend in # locations (decline, stable, increasing, unknown):
The number of spawning populations declined from three to one over the last three decades of the 20th century.
Are there extreme fluctuations in # locations (>1 order of magnitude)?
No
Habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat:
Areas historically used for spawning, incubation and rearing in the Saint John and Annapolis rivers appear to have been altered, which may be the cause of the disappearance of these two populations. No evidence of change in Shubenacadie River spawning habitats or in feeding areas in the Bay of Fundy.

Population information

Generation time (average age of parents in the population):
12 years.
Number of mature individuals:
Total size of the three populations, when they co-existed: unknown. See on next page, total size of the Shubenacadie River population.
Total population trend:
The total number of striped bass of Canadian origin in the Bay of Fundy likely declined in the 20thcentury, since two of the three populations are now extirpated. However, the size of the extirpated populations areas never estimated.
If decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period):
Unknown
Are there extreme fluctuations in number of mature individuals ( 1 order of magnitude)?
Unknown
Is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., ≤ 1 successful migrant / year)?
No, not currently, because there is only one extant population.
List each population and the number of mature individuals in each:
Shubenacadie River: In 2002, over 15,000 bass of age 3+ years, 7,000 of which were of age 4+ years.
Specify trend in number of populations (decline, stable, increasing, unknown):
Shubenacadie River: only one population estimate. Trend not yet determined.
Are there extreme fluctuations in number of populations (>1 order of magnitude)?
Unknown

Threats (actual or imminent threats to populations or habitats)

  • Exploitation: In the Bay of Fundy, undetermined effect on the Shubenacadie population, which is taken along with U.S. bass; bycatch in gear set in Minas Basin.
  • Habitat alterations: undetermined risk related to mining activities (titanium) in the Shubenacadie River and Cobequid Bay.
  • Introduction of species: Chain pickerel (Esox niger) in Grand Lake (in the Shubenacadie River system), bass overwintering site; possible effect not yet determined.

Rescue Effect (immigration from an outside source)

Likely low, according to available information.

Does species exist elsewhere (in Canada or outside)?
Yes
Status of the outside population(s)?
In the northwest, the St. Lawrence population has disappeared. In the north, there is one extant population in the southern Gulf (Miramichi River).
USA
Along the Atlantic coast of the US, the species is abundant (see NatureServe rankings below).
Is immigration known or possible?
Mark-recapture data indicate very little contact with the population to the north. Individuals from US populations feed during the summer in the Bay of Fundy, but there is no evidence that these individuals spawn in Canadian waters.
Would immigrants be adapted to survive here?
Unknown
Is there sufficient habitat for immigrants here?
See comments above.

Quantitative Analysis

Data not available.

Current Status

NatureServe Ranks (NatureServe 2004)

Global Status:
G5
National Status:
CanadaN3?; USAN5
Provincial / State Status: 
Canada: NB (S2), NS (S1), PE (S2N), QC (SX.
USA (selected states): Connecticut (S3), Delaware (S5), Maine (S5), Maryland (S5), Massachusetts (SU), New Hampshire (S4), New Jersey (S4), New York (S4), Rhode Island (SNR), Virginia (S4)

Status and Reasons for Designation

Status:
Threatened
Alpha-numeric code:
Met criteria for Endangered, A2bc, but designated Threatened, A2bc; D2, because the one remaining spawning population does not appear to be at imminent risk.
Reasons for Designation:
Repeated spawning failures led to the disappearance of the Annapolis and Saint John River populations. These disappearances are thought to be due to changes in flow regime and poor water quality. In the Shubenacadie River population, the presence of the introduced chain pickerel in overwintering sites may constitute a threat. Another threat to the population is bycatch from various commercial fisheries. The Bay of Fundy is also used by striped bass breeding in rivers in the United States. These fish were not assessed.

Applicability of Criteria

Criterion A (Declining Total Population): In the last 2 generations, two of three spawning populations have been lost. Qualifies for Endangered under A2(bc).

Criterion B (Small Distribution, and Decline or Fluctuation): Although it meets the threshold for Endangered in terms of area of occupancy and small number of locations, neither a continuing decline nor extreme fluctuations can be demonstrated.

Criterion C (Small Total Population Size and Decline): Does not meet thresholds.

Criterion D (Very Small Population or Restricted Distribution): Qualifies as Threatened under D2 because it is only known from one spawning location.

Criterion E (Quantitative Analysis): Data are not available.

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