Western silvery minnow (Hybognathus argyritis) COSEWIC assessment and status report: chapter 11
Technical Summary
Hybognathus argyritis
Western silvery minnow – Méné d’argent de l’Ouest
Extent and Area Information
Population Information
Threats (actual or imminent threats to populations or habitats)
Immediate
- Low flows and high water temperatures resulting from drought and surface water extractions
- Introduced exotic species
- Anoxia in overwintering habitat related to water diversions
Potential
- Surface and ground water extraction
- Low flows and high water temperatures resulting from drought exacerbated by climate change
- Dam and reservoir construction
- Livestock and agricultural uses of the floodplain
- Canal maintenance and drought
Quantitative Analysis
No data
Current Status
Nature Conservancy Ranks (NatureServe 2007)
- Global – G5 (Secure)
- National
- US – N4 (Secure)
- Canada – N3N4 (May be at Risk)
- Regional
- US
- IL – S2 (Vulnerable),
- IA – S1 (Critically Imperilled),
- KS – S2,
- MO – S2,
- MT – S4S5 (Possibly Secure).
- NE – S5 (Secure),
- ND – SNR (Not Ranked),
- SD – S5,
- WY – S2.
- Canada
- AB – S1
- US
Wild Species 2005 (Canadian Endangered Species Conservation Council 2006)
- Canada – 2 (May Be At Risk)
- Alberta – 1 (At Risk)
COSEWIC
- Threatened 2001
- Endangered 2008
SARA
- Schedule 1 Part 3 – TH
Status and Reasons for Designation
Status: Endangered
Alpha-numeric code: B1ab(iii)+2ab(iii)
Reasons for Designation: This small minnow species is restricted to the Milk River in Southern Alberta, a region characterized by drought conditions of increasing frequency and severity. While the future of flow regimes associated with the St. Mary’s diversion canal and proposed water storage projects are uncertain, consequences of these activities have the potential to significantly affect the survival of the species. Rescue effect from U.S. populations is not possible.
Applicability of Criteria
Criterion A (Declining Total Population): Not Applicable – no evidence of decline in the total number of mature individuals.
Criterion B (Small Distribution, and Decline or Fluctuation): Met criteria for Endangered B1ab(iii)+2ab(iii), as the EO (1200 km²) and AO (244 km²) are below threshold values, there is only one known location, and the area, extent and/or quality of habitat is impacted by water flow regimes resulting from water extraction for irrigation, and predicted increase in frequency and severity of drought conditions.
Criterion C (Small Total Population Size and Decline): Not Applicable – number of mature individuals is unknown and there is no evidence of decline in the number of mature individuals.
Criterion D (Very Small Population or Restricted Distribution): Met criteria for Threatened D2 – only one location.
Criterion E (Quantitative Analysis): Not Applicable – no data.
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