Fish & wildlife Success stories Kootenai

 
Success stories — Kootenai River

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Kootenai Tribe is working to recover dwindling sturgeon population

In Bonners Ferry, Idaho, the Kootenai Tribe is racing against the extinction clock to save a unique white sturgeon population that has inhabited the Kootenai River for millennia but that has not reproduced in sustainable numbers in at least 30 years. Sturgeon can live to be 100, but the Kootenai population is aging and unless more young fish live to spawning age the species likely will be extinct in as few as 20 years.

The U.S. Fish and Wildlife Service listed Kootenai River white sturgeon as an endangered species on September 6, 1994. Four years earlier, the tribe initiated the Kootenai River White Sturgeon Study and Conservation Aquaculture Project to preserve the genetic variability of the population, begin rebuilding natural age class structure with hatchery-reared fish, and prevent extinction while measures are implemented to restore the natural production of fish. Consistent with the project’s breeding plan and the Fish and Wildlife Service’s recovery plan, the tribe has been successfully incubating, hatching, raising and releasing sturgeon using the eggs and sperm of adult fish taken from the river and later returned. Subsequent monitoring shows the juveniles are surviving. But sturgeon don’t reach spawning maturity until about age 20. Meanwhile, mature fish have spawned naturally in the Kootenai, but the eggs or the resulting juveniles don’t appear to be surviving in numbers sufficient to rebuild the population.

Many changes to the natural ecosystem have occurred over the past decades, but one of the most significant changes was the construction and operation of Libby Dam, which altered the historic flow pattern in the lower Kootenai River, reducing the annual spring flows by half. The spring flows apparently were important for sturgeon spawning and recruitment, as successful recruitment has not been recorded since 1974 — one year before the dam became fully operational. Other changes to the ecosystem include diking and diversions resulting in the loss of riparian, slough and side-channel habitat, as well as the loss of productivity.

Susan Ireland, fish and wildlife program manager for the tribe, said the goal of the aquaculture project is to protect the sturgeon from extinction until suitable habitat conditions are re-established in the Kootenai River ecosystem so that sturgeon survival can improve beyond the egg/larval stage and natural recruitment of juvenile fish into the population can be restored. The program is designed to produce four to 12 separate sturgeon families per year and up to 100 adults per family that survive to breeding age. The work is being coordinated with U.S. federal and state fish and wildlife agencies, and also with counterpart agencies in British Columbia, as Kootenai River sturgeon migrate back and forth across the border.

During the 11 years between 1992 and 2003, the conservation aquaculture program has released over 40,000 juvenile sturgeon of ages between 1 and 4 years. Subsequent studies showed that survival was about 60 percent for the first year in the river and 90 percent after that. The studies also showed that most of the fish in the river were bred in the hatchery. Recent capture of 659 juvenile fish by Idaho Department of Fish and Game showed that only 39 were of wild origin.

In light of the low number of wild juvenile fish and the decline in the wild adult population, the tribe and its partners in the recovery effort decided to revise the breeding program. The new program, issued in March, calls for spawning more fish and releasing more families, representing 3,000 - 4,500 fish per family annually — about double the previous amount — and releasing them at smaller sizes and younger ages. This is appropriate, Ireland said, because the next generation of fish will be almost entirely of hatchery origin. Producing more families and releasing larger numbers of fish per family should ensure that genetic diversity of the species is maintained and that sufficient numbers of fish survive the 20 or more years to spawning maturity, she said. The revised program also calls for releasing fish at more locations to take advantage of suitable habitat.

“We’re taking an adaptive approach so that we can modify the plan as necessary, based on analysis of data,” Ireland said. “We are in a race against extinction.”

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