COSEWIC assessment and update status report on the Chiselmouth in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures, Tables and Appendices
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status
- Summary of Status Report
- Technical Summary
- Acknowledgements and Literature Cited
- Biographical Summary of the Author and Authorities Consulted
- Appendix 1: Freshwater Fishes Species Specialist Subcommittees Information
Extent and Area Information
Likely stable, although several small lake populations deliberately extirpated
Fluctuations in extent of occurrence
Area of Occupancy
<500 km2 several hundred linear km of stream length; half a dozen lakes
Fluctuations in area of accupancy
Unknown, but unlikely
Number of extant locations
Present in at least 8 major drainages
Trend in # locations
Fluctuations in # locations
No. locations from which populations have been extirpated
Several (deliberate, but exact number unknown)
Number of mature individuals in the Canadian population
10 000 – 30 000 (estimate)
Fluctuations in number of mature individuals
Are populations fragmented?
Populations are relatively isolated from one another, but the exchange rate of individuals between pops. Is unknown
Populations and the number of mature individuals in each
(L = 2000-5000 M = 1000-2000
S = < 1000)
1) Blackwater/Nazko/Euchi niko L
2) Salmon/Muskeg S
3) Similkameen M
4) Okanagan L
5) Kettle L
6) Upper Chilcotin S
7) Nicola L
8) Shuswap M
Trend in number of populations
Fluctuations in number of populations
- Cumulative impacts of agriculture, forestry, and livestock grazing may be impacting chiselmouth in some rivers (e.g. Okanagan, Nicola), and these impacts will likely get worse in the near future.
- Populations in some lakes may be subject to extermination as competitors of game fish species.
Rescue Effect: Low for most pops.
Does species exist elsewhere in Canada?
In the U.S.?
Yes – ID, NV, OR and WA
Status of the outside populations?
ID-S5, NV-S?, OR-S4, WA-S4
Is immigration known or possible?
Dams and natural barriers prevent most natural migration
Would immigrants be adapted to survive here?
For Columbia R. pops, likely; possibly not for Fraser basin pops.
Is there sufficient habitat for immigrants here?
National U.S. N5
Regional U.S. ID - S5, NV – S?, OR – S4, WA – S4
Canada BC – S3, Provincial Listing Blue (Special Concern)
COSEWIC– DD 1997
Status Designated May 2003
Not At Risk
Reasons for Status Designation
The Canadian distribution of this species is restricted to a few disjunct populations in south-central British columbia where they are found in low densities, but appear to be stable and are not subject to any known factors that could put them at risk.
- Date Modified: