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  3. > Recovery Strategy for the Alberta populations of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) in Canada: Table 1
Table 1. Detailed threats assessment for westslope cutthroat trout in Alberta.
Threat Category Threat (Threats are not listed in any particular order.) Activity/Detail Likelihood of Occurrence (H= High, M=moderate, L=Low. Codes are further explained in Appendix A) (Where a separate rating is not given for National Parks, the rating is the same inside and outside National Parks, unless the comments indicate this threat does not apply.) Extent of Occurrence (H= High, M=moderate, L=Low. Codes are further explained in Appendix A) (P=Past, C=Current, F=Future, ? = data deficient, NP=National Parks). Codes are further explained in Appendix A.) Severity of Impact (H= High, M=moderate, L=Low. Codes are further explained in Appendix A) (P=Past, C=Current, F=Future, ? = data deficient, NP=National Parks). Codes are further explained in Appendix A.) Immediacy of Impact (P=Past, C=Current, F=Future, ? = data deficient, NP=National Parks). Codes are further explained in Appendix A.) Threat Significance (H= High, M=moderate, L=Low. Codes are further explained in Appendix A) (P=Past, C=Current, F=Future, ? = data deficient, NP=National Parks). Codes are further explained in Appendix A.) Mitigation Potential (H= High, M=moderate, L=Low. Codes are further explained in Appendix A) (P=Past, C=Current, F=Future, ? = data deficient, NP=National Parks). Codes are further explained in Appendix A.) Comments
Invasive Species  Hybridization and competition Rainbow trout H H
M (NP)
H
M (NP)
P,C,F H L No stocking currently occurs in areas where rainbow trout could threaten pure remnant westslope cutthroat trout populations but stocking policy to be reviewed.
Opportunities to mitigate in stream systems is low but in lakes may be moderate-high.
Yellowstone cutthroat trout H L L P,C,F M L Found in some national park waters and in Island Creek (Crowsnest drainage). Severity high for Island Creek population.
Opportunities to mitigate in stream systems is low but in lakes may be moderate-high.
Golden trout ? L ? P,C,F ? M Four lakes in Castle drainage and possibly in Temple Lake (BNP). Uncertain if lake populations have migrated into downstream systems. Also uncertain if the two species hybridize.
Opportunities to mitigate in stream systems is low but in lakes may be moderate-high.
Competition Brook trout H H H P,C,F H M Includes competition, range constriction or elimination of native species.
No stocking currently occurs in areas where brook trout could threaten pure remnant westslope cutthroat trout populations but stocking policy to be reviewed.
Opportunities to mitigate in stream systems is low-moderate but in lakes may be moderate-high.
Brown trout H M M-H P,C,F M
H (NP)
L Includes competition, range constriction or elimination of native species.
No stocking currently occurs in areas where brown trout could threaten pure remnant westslope cutthroat trout populations but stocking policy to be reviewed.
A serious threat where they occur, but more of an issue in medium to large systems e.g., Bow, Kananaskis, Crowsnest, lower Oldman, Waterton rivers.
Lake trout L
H (NP)
L
M (NP)
M
H (NP)
P,C,F L
H (NP)
L
L-M (NP)
Lake trout stocked into some waterbodies and others thought to be in native range. Found in Crowsnest, Waterton Lakes as well as in Spray Lakes, Ghost and Bearspaw Reservoirs. Possibly naturally co-occurring in Lake Minnewanka. In reservoirs, native species have typically been reduced in abundance or extirpated. Where the two species naturally co-occur the threat significance is low, however, where lake trout are introduced, the threat significance is high.
Bow and Hector lakes mitigation potential is low to moderate.
Algae Didymosphenia geminata ? L ? C,F ? ? Freshwater algae; single cells are capable of expanding into large mats that can completely cover stream bottoms, reducing available habitat for fish and invertebrates.
Insufficient information to further evaluate at this time.
Pathogens Parasites L L H C,F L M Limited information available. Whirling disease is of concern but does not currently occur in Alberta. Moderate mitigation potential in terms of introduction of pathogen.
If whirling disease were to enter Alberta, the waters most likely to be affected would be the lower portions of watersheds, as opposed to the headwater streams where most of the remaining westslope cutthroat trout populations are found (see text for explanation).
Adverse Effects on Habitat    Changes in flow Dam/Reservoir operation H M
H (NP)
H P,C,F H L-M Loss of riverine and spawning habitat, transform flow regime in downstream habitats, reduce downstream flow (e.g., irrigation dams and weirs), decreased high flows and increased low flows, decreased movement of stream bed material and LWD. Depends on purpose i.e., power, municipal, irrigation. Possible future dams and diversions.
Forest removal - harvest H M-H
L (NP)
M
L (NP)
P,C,F M-H
L (NP)
M Increased peak flow, altered snow interception and melt processes, increased run-off, increased summer temperatures (due to changes in channel form i.e., widening of channel and shallower) and reduced late summer and winter flows. Appropriate riparian buffer width required. Uncertainty regarding effects of changes in flow depending on timing of change. Severity may change depending on space and time. 
Forest removal - fire H H
L (NP)
L-H
L (NP)
P,C,F M-H
L (NP)
L Increased summer temperatures. Ratings would depend on forest fire severity.
Water extraction – surface and groundwater H M M
L (NP)
P,C,F M-H
L (NP)
M-H
M (NP)
Snow making, gas plants, hydrostatic testing, instream construction (upset). Uncertainty for groundwater extraction which could result in high threat significance, unknowns concerning connectivity between ground and surface water.
Sedimentation Forest harvest, linear disturbance, grazing, OHVs, recreational access, instream construction, municipal run-off H
M (NP)
H
L (NP)
M-H
M (NP)
P,C,F H
L (NP)
M-H
H (NP)
Especially a problem if occurs in or upstream of spawning areas. Potential for high severity impact on small, isolated populations.
Use of OHVs as an activity is unpredictable, therefore, the extent and severity are hard to assess.
Habitat loss Dam and reservoir creation H
H (NP)
M M-H P,C,F
P,C (NP)
M-H L-M Associated with dams, smaller scale water storage, often stocked with non-native species, often low productivity, water level fluctuations destroy littoral zone. Destroy fluvial spawning habitats. Resulting in decreased bedload movement to areas downstream, as well as lack of scouring flows to clean fines out of substrate.
Severity moderate to high – extirpation could be related to combination of introduction of non-native species and habitat loss.
Mitigation potential could be moderate for any new dams or reservoirs (location, fish passage).
Habitat fragmentation (loss of connectivity) Dams, culverts H H H P,C,F H L-H Block upstream and/or downstream fish movements. Loss of migratory life history forms (fluvial, adfluvial). Inability to access habitats to meet all life history requirements.
Mitigation potential is low for dams but moderate to high for culverts.
Consider impassable barriers that separate natives and non-natives before initiating corrective actions.
Habitat alteration and loss   Linear disturbance
(e.g., roads, pipelines, railway, OHVs, recreational trails, culverts)
H H H P,C,F H M Increased surface erosion and run-off, fine sediment deposition, increased access, physical loss of habitat from construction and use (e.g., footprint), barriers to movement (e.g., impassable culverts). Impact of each linear disturbance may be local but cumulatively can result in significant overall negative effects on habitat quality and quantity.
Grazing   H H M P,C,F M M Riparian disturbance, changes to stream structure, fine sediment delivery.
Common land-use throughout species range. Can result in redds being trampled or silted in and destruction of riparian habitat and undercut banks.
Typical entry/exit dates for cattle grazing are early June to mid-October.
Not applicable to national parks.
River training H L M-H P,C,F M M Bank armouring, channelization from a variety of causes e.g., road crossings, protection of property, flood prevention, urban areas. Loss of high quality habitat (e.g., undercut banks, sweepers and log jams). Extent of occurrence and severity are high in urban areas.
Consumptive Use/ Exploitation     Harvest   Intentional mortality M
L(NP)
L L P,C,F
P (NP)
L H Legal harvest. Catch-and-release, size limits implemented for sensitive fisheries. Most harvest permitted on stocked fisheries.
Incidental or accidental mort H M
L(NP)
L-M? P,C,F L? M Hooking mortality of released fish, fish misidentification resulting in harvest, scientific sampling. Uncertainty around angler pressure.
Illegal (poaching) H M L-M? P,C,F L-M? M Consider potential for closing fisheries to result in increase in poaching and illegal introductions. Could also include angler misidentification.
Stocking   Current legal stocking of native fish Westslope cutthroat trout L M L C,F L H Stocking on top of native populations may have occurred in the past but records are frequently unreliable or unavailable.
Stocking is currently limited to high mountain lakes or beaver ponds with no or limited connectivity to downstream habitats but stocking policy to be reviewed.
Likelihood of occurrence is rated high as a result of past stocking practices which have had an unknown effect on some populations.
Not applicable to national parks.
Current legal stocking of non-native fish Rainbow trout, brook trout, brown trout H M M-H C,F L H Severity high as a result of past stocking practices. No stocking currently occurs on top of or upstream of existing pure remnant westslope cutthroat trout populations. However, it may occur in a few areas where populations are already severely hybridized or where triploid fish are used. Stocking policy to be reviewed.
No stocking in national parks.
Illegal stocking of non-native fish Many potential species H
L (NP)
M
L (NP)
L-H
L (NP)
P,C,F L-H
L (NP)
M
H (NP)
Depends on the species, locations of introductions. Could compromise small systems currently dependent on a barrier.
Pollution  Water quality and fish habitat degradation Point source - includes accidental spills associated with road/rail and pipeline crossings H L-H L-H C,F M L-M Effects depend on substance released, location of spill, potential to mitigate impacts.
Non-Point source - surface run-off (e.g., road salt, incr. nutrients as a result of fires) H M M P,C,F M M High flows, agricultural and urban run-off, elevated sediment, nutrients etc. 
Climate Change Climate change and severe weather Increasing temperature trend, altered flow regimes, droughts, high flow events H H M-H C,F M-H L Changes in water temperature, basin hydrology, channel morphology, riparian habitat, stream flows, habitat quality and availability, competitive advantage to non-native fish.
Threats evaluation based on modeling scenarios for changes in mean annual precipitation and temperature from 2020s to 2080s. See Mayhood (2009) for details.
Severity range based on various modelling scenarios. Depends on location and timing of changes.

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Date Modified:
2014-04-04