Acipenser transmontanus (Kootenai River subpopulation)
| Kingdom |
Phylum |
Class |
Order |
Family |
| ANIMALIA |
CHORDATA |
ACTINOPTERYGII |
ACIPENSERIFORMES |
ACIPENSERIDAE |
| Scientific Name: |
Acipenser transmontanus (Kootenai 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: |
Endangered
B1ab(i,v); C1
ver 3.1
|
| Year Assessed: |
2004 |
| Assessor/s: |
Duke, S. (U.S. Fish & Wildlife Service) |
| Reviewer/s: |
St. Pierre, R. & Pourkazemi, M. (Sturgeon Red List Authority) |
Justification:
A natural barrier at Bonnington Falls downstream of Kootenay Lake has isolated this subpopulation from other white sturgeon subpopulations in the Columbia River basin since the last glacial age approximately 10,000 years ago. The subpopulation is restricted to approximately 270 km of the Kootenai River and Kootenay Lake.
The Kootenai River subpopulation of white sturgeon has been in general decline since the mid-1960's (Apperson and Anders 1991, Duke et al. 1999). The remaining wild population is comprised primarily of adult sturgeon older than 25 years, with very little recruitment observed in the wild population since the mid-1970's (Duke et al. 1999, Ireland et al. 2000). In 1997, there were an estimated 1,468 adults (95% CI: 740 to 2,197) and 17 juvenile white sturgeon (Paragamian et al. 1997).
The Kootenai River white sturgeon recovery plan describes a series of 46 specific conservation measures in the United States and Canada that are believed necessary to recover the endangered white sturgeon. Recovery objectives are to re-establish successful reproduction in the wild by increasing Kootenai River flows and producing hatchery-reared juveniles over the next 10 years to prevent extinction. Based on ongoing implementation of the recovery actions, it is currently unknown whether flow augmentation will be effective in restoring successful natural reproduction in the near future, consequently it is projected that the wild adult Kootenai River white sturgeon subpopulation will decline well into the future.
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| History: |
| 1996 |
– |
Endangered
(Baillie and Groombridge 1996)
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Geographic Range
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| Range Description: |
The Kootenai River subpopulation is a land-locked subpopulation restricted to approximately 270 km of the Kootenai River in Idaho and Montana (United States), and Kootenay Lake in British Columbia (Canada), primarily upstream from Cora Linn Dam at the outflow from Kootenay Lake.
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| Countries: |
Native:
Canada (British Columbia); United States (Idaho, Montana)
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Population
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| Population: |
The Kootenai River subpopulation of white sturgeon has been in general decline since the mid-1960's (Apperson and Anders 1991, Duke et al. 1999). The remaining wild population is comprised primarily of adult sturgeon older than 25 years, with very little recruitment observed in the wild population since the mid-1970's (Duke et al. 1999, Ireland et al. 2000). In 1997, there were an estimated 1,468 adults (95% CI: 740 to 2,197) and 17 juvenile white sturgeon (Paragamian et al. 1997).
Beginning in 1991 prior to official action under the Endangered Species Act, the U.S. Army Corps of Engineers and Bonneville Power Administration provided Kootenai River flows from Libby Dam to aid Kootenai River white sturgeon recruitment. These flows, considered experimental from 1991 through 1995, were intended to identify various factors limiting successful reproduction of Kootenai River white sturgeon and help achieve recovery. Beginning in 1995, there was acknowledgment that an adaptive approach was needed since the precise relationship between annual timing, magnitude, temperature, and duration of flows downstream of Libby Dam necessary for successful sturgeon reproduction had not been demonstrated. Since that time, the operation of Libby Dam has included a spring refill period depending upon runoff forecasts, for conservation storage following drafting during the winter flood control season in an attempt to better mimic natural flow regime more closely (Duke et al. 1999). To date, the increased Kootenai River flows provided through the flow augmentation program has resulted in documented spawning each year but not survival beyond the egg stage. Consequently natural recruitment has not been significantly restored. Only a total of 18 wild juvenile white sturgeon have been collected since 1993, with the largest year class appearing to be 1991 with ten wild recruits. It is currently unknown whether flow augmentation will be effective in restoring successful natural reproduction in the near future, consequently it is projected that the wild adult Kootenai River white sturgeon subpopulation will decline well into the future.
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| Population Trend: |
Decreasing
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Habitat and Ecology
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| Habitat and Ecology: |
This subpopulation is land-locked and is restricted to freshwater habitats.
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| Systems: |
Freshwater |
| Major Threat(s): |
For more than the last 100 years, human development has modified the natural hydrograph of the Kootenai River through such activities as Libby dam construction and operation, dyke construction and lowered Kootenai Lake levels. These activities have altered white sturgeon spawning, egg incubation, nursery and rearing habitats, and reduced overall biological productivity. Although these factors may have contributed to a general lack of recruitment of this unique population of white sturgeon during the last century, the operation of Libby Dam in 1974 is considered to be a primary reason for the population’s continued decline (Apperson and Anders 1991). When Libby Dam began regulating the Kootenai River, average spring peak flows were reduced by more than 50% and winter flows increased by more than 300%.
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Conservation Actions
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| Conservation Actions: |
On September 6, 1994, the U.S. Fish and Wildlife Service listed the Kootenai River population of white sturgeon as endangered under the Endangered Species Act (Act). Subsequently, a recovery team composed of two Canadians and eight Americans was formed in January 1995. The team completed a final recovery plan (Plan) for the Kootenai River white sturgeon in 1998, which was subsequently approved by the U.S. Fish and Wildlife Service in late 1999 (Duke et al. 1999).
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