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Recovery Strategy for the Western Silvery Minnow (Hypognathus argyritis) in Canada [Proposed]

Table 2. Detailed threats assessment for western silvery minnow.
SourceLikelihood of Occurrence*Extent of Occurrence*Severity of Impact*Immediacy of ImpactThreat Signi-ficance*Mitigation Potential*Comments
Species IntroductionsLegal or illegal stockingMHL-HC, FL-HLDepends on species involved.
Habitat Loss/ DegradationChanges in FlowHHHFHLPossible canal options include achieving current design capacity, capacity increase (24.1-28.3 m³/s; 850-1,000 cfs) or abandonment.
 Canal MaintenanceHHHFHMRecommend to Alberta Environment that canal maintenance or repairs be delayed until the non-augmented period whenever possible.
 Dam construction and operationMHHFHLThis complex issue cannot be fully evaluated until proposal details are available; however general problems associated with dams elsewhere are recognized here.
 Groundwater ExtractionHHL?PL?LCould be significant during non-augmented period, but difficult to evaluate due to inability to quantify natural losses or needs of minnow.
 Surface Water Extraction - IrrigationHMLPLMIrrigation only occurs during the augmentation period.
 Surface Water Extraction - Non-irrigationHHHPHMFish most vulnerable during non-augmented period. Restriction of Temporary Diversion Licences during critical low flows could help mitigate impacts.
 Livestock Use of Flood PlainMMLP mainly, CM?HAgricultural practices along rivers are generally conservative but some cattle access still occurs and impacts are unknown. The Alberta Riparian Habitat Management Society (Cows and Fish) has been advising producers on best practices, with positive results.
PollutionPoint SourceMHHFMLIncludes accidental spills associated with road/rail  and pipeline crossings, depends in part on substance released, location of spill and potential to mitigate the impacts, gas leaks are known to have occurred at river crossings in recent years
 Non-Point SourceLLLPLMBecause of the high flows during growth period, unlikely that agricultural run-off has a big impact
 AnoxiaH??P?LExtent and severity unknown but could be significant during the winter depending on availability of open water areas
Natural ProcessesDroughtHHHP, FHLDepends on the length and severity of drought
 Climate change?H???LImpossible to evaluate at this time, mitigation not possible at local level
Other ThreatsScientific samplingHHLPLHThe threat from further sampling is likely low and can be controlled.

 *H= High, M=moderate, L=Low.   **P=Past, C=Current, F=Future