Acipenser transmontanus (Nechako River subpopulation)
| Kingdom |
Phylum |
Class |
Order |
Family |
| ANIMALIA |
CHORDATA |
ACTINOPTERYGII |
ACIPENSERIFORMES |
ACIPENSERIDAE |
| Scientific Name: |
Acipenser transmontanus (Nechako River subpopulation) |
| Species Authority: |
Richardson, 1836 |
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Common Name/s:
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Assessment Information
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| Red List Category & Criteria: |
Critically Endangered
E
ver 3.1
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| Year Published: |
2004 |
| Assessor/s: |
Down, T. & Ptolemy, J. (Ministry of Water, Land & Air Protection, Canada) |
| Reviewer/s: |
St. Pierre, R. & Pourkazemi, M. (Sturgeon Red List Authority) |
Justification:
A recent analysis (Korman and Walters 2000), using a population dynamics model for the Nechako River subpopulation of white sturgeon, indicates this subpopulation will be effectively extinct within 20 to 30 years (at current rates of decline). "Effectively extinct" was defined as < 50 individuals which are vulnerable to the sampling gear employed to collect the data utilized the model.
Mark recapture estimates for the subpopulation (R.L. and L Environmental Services Ltd. 2000) estimate the current population as 571 (95% CI = 421?890). In the Nechako, flow reduction has reduced depth and the amount of habitat available in side channels and backwaters.
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Geographic Range
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| Range Description: |
Restricted to the Nechako River and it?s tributary the Stuart River (these two have a combined stream length of about 400 km). However, sturgeon are not evenly dispersed throughout this length of river, but are clustered in suitable habitat.
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| Countries: |
Native:
Canada (British Columbia)
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| Range Map: |
Click here to open the map viewer and explore range.
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Population
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| Population: |
The preliminary estimate for first spawning in females of the mid-river population is late 20's with males possibly reaching maturity before 20 years. In the Nechako River preliminary information indicates females may not reach maturity until their late 30?s, or older, and males may not spawn until their early 40?s (this estimate may be skewed by the lack of younger fish in the population). The oldest fish sampled was 88 years of age. Generation length in the Nechako subpopulation could be 50 to 55 years.
Mark recapture estimates for the Nechako subpopulation (R.L. & L Environmental Services Ltd. 2000) estimate the subpopulation at 571 (95% CI = 421?890). Very few fish less than 30 years of age were sampled, indicating a near total recruitment failure. Only 4% of the individuals sampled were in the juvenile size class (less than 100 cm total length), in spite of a directed sampling effort on this life stage.
RL&L used a size of > 150 cm (called oversize) to separate adult individuals from sub-adults and juveniles. On this basis, 80% of the fish sampled in the Nechako subpopulation were in the adult size class. RL&L found the sex ratio was skewed 2:1 to males in this subpopulation. Fewer than 10% of the females and 12% of the males examined in the adult size class were in the late reproductive stages, indicating that the proportion of reproductively mature individuals in a given year is quite low.
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| Population Trend: |
Decreasing
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Habitat and Ecology
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| Habitat and Ecology: |
Restricted to freshwater habitat in the Nechako River and its tributary the Stuart River.
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| Systems: |
Freshwater |
| Major Threat(s): |
In the Nechako, flow reduction has reduced depth and the amount of habitat available in side channels and backwaters.
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Bibliography
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IUCN. 2004. 2004 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 23 November 2004.
Korman, J. and Walters, C. 2000. Status and potential recovery for the Nechako River white sturgeon stock. Prepared for BC Fisheries. Victoria, BC.
RL&L Environmental Services Ltd. 2000. Fraser River white sturgeon monitoring program comprehensive report (1995 to 1999). Prepared for BC Fisheries. Victoria, BC. 94 p.
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