Green sturgeon (Acipenser medirostris) COSEWIC assessment and status report: chapter 14

Technical summary

Acipenser medirostris
Green sturgeon

Esturgeon vert

Range of Occurrence in Canada: British Columbia (BC)


Extent and area information

Extent of occurrence (EO) in Canada.
[Estimated from Figure 4 ]
<500 000 km 2
Specify trend.
Unknown, possible decline
Are there extreme fluctuations in EO (> 1 order of magnitude)?
Unknown
Area of occupancy (AO) (km 2 ) [Estimate of author].
Data limited; maximum 12 000 – 30 000 km2
Specify trend.
Unknown, possible decline
Are there extreme fluctuations in AO (> 1 order of magnitude)?
Yes, summer concentrations
Number of extant locations.
Unknown in marine, at least 2 in freshwater
Specify trend in # locations.
Unknown
Are there extreme fluctuations in # locations (>1 order of magnitude)?
Unknown
Habitat trend:
Stable


Population information

Generation time.
27 to 33 years
Number of mature individuals (capable of reproduction) in the Canadian population.
Unknown
Total population trend:
Unknown, possibly declining
If decline, % decline over the last/next 10 years or 3 generations, whichever is greater.
Unknown
Are there extreme fluctuations in number of mature individuals (> 1 order of magnitude)?
Unknown
Is the total population severely fragmented?
No
List each population and the number of mature individuals in each.
Not Applicable
Specify trend in number of populations (decline, stable, increasing, unknown).
Unknown
Are there extreme fluctuations in number of populations?
Unknown


Threats (actual or imminent threats to populations or habitats)

Anthropogenic activities known to impact sturgeons include: blockage of available freshwater spawning habitat through diking, damming causing inadequate flow regimes, channelization, elimination of backwater areas, dewatering of streams, destruction of thermal refugia, loss of deep pools, inundation of habitat by reservoirs, exposure to bioaccumulating industrial and municipal pollution, and overfishing. With the exception of overfishing, the majority of these impacts are restricted to the freshwater phases of green sturgeon life history. As green sturgeon are rarely captured in freshwater in Canada, negative anthropogenic impacts outside fishing may be more limiting to individuals utilizing spawning and rearing habitat in the US.


Rescue effect (immigration from an outside source): Moderate

Does species exist elsewhere (in Canada or outside)?
Yes
Status of the outside population(s)?
Possibly declining
Is immigration known or possible?
Yes
Would immigrants be adapted to survive here?
Unknown
Is there sufficient habitat for immigrants here?
Yes


Quantitative Analysis

Not Applicable


Existing status

Nature Conservancy Ranks
  Global - G3
  National
    US - N3
    Canada N3N
  Regional
    US - Alaska - S4N, California S2S2, Oregon S3, Washington S3N
    Canada - BC S3N

International Union for Conservation of Nature (IUCN) - Vulnerable
US Endangered Species Act - Candidate species
Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) - Appendix II
Committee on the Status of Endangered Wildlife in Canada (COSEWIC) - SC 1987


Status and reasons for designation

Status: Special concern
Alpha-numeric code: Not applicable


Reasons for Designation: The number of individuals in Canadian waters is unknown, but is undoubtedly not large. This species is globally at risk and is of concern in Canada because of exploitation and habitat loss due to damming of rivers.


Applicability of criteria

Criterion A (Declining Total Population): Not applicable, no evidence of population decline.

Criterion B (Small Distribution, and Decline or Fluctuation): Not applicable, AO and EO larger than threshold values and there is no evidence of decline or fluctuation.

Criterion C (Small Total Population Size and Decline): Not applicable, population size and trends not known.

Criterion D (Very Small Population or Restricted Distribution): Not applicable, although the Canadian population is undoubtedly small, the number of mature individuals is unknown, the area of occupancy is certainly larger than the threshold value, and the number of locations at which the species is found is uncertain.

Criterion E (Quantitative Analysis): Not applicable - no data.

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