Saving an Ice Age Relic
Kootenai River white sturgeon in danger of extinction
Diminishing at a rate of four percent a year, the Kootenai River white sturgeon population is in danger of extinction unless a solution is found. The population has been declining for the last four decades, with between 500 and 1,000 sturgeon remaining. Biologists and scientists are searching for answers for this ice age relic.
Since the last ice age, thousands of white sturgeon have swam the Kootenai River between Kootenai Falls in Montana and Kootenay Lake in British Columbia. Then, in the 1960s, biologists noticed limited recruitment (fewer young fish surviving). In 1994, the Kootenai River white sturgeon was added to the Endangered Species list.
There is no straightforward answer to the population’s decline, but the decline may be related to changes in the river’s ecosystem. Dikes along the Kootenai River disconnected the floodplain and vital wetlands from the river. The completion of Libby Dam in 1972 changed the flow regime of the river and eliminated historic spring floods.
“Historic spring floods used to scour the river bottom and remove the sand covering the cobbles and gravels,” says Vaughn Paragamian, Idaho Fish and Game Biologist. “But with the altered ecosystem, those cobble substrates are now covered with sand. Sturgeon are spawning in the same areas as pre-Libby Dam, but they are spawning over moving sand dunes. Just a quarter of an inch of sand will suffocate an egg.”
Currently, the sturgeon are only spawning downstream of the bridge in Bonners Ferry in sandy substrate. Biologists are unsure why the sturgeon will not swim above the bridge to spawn in suitable substrate consisting of cobbles and gravels. However, they have discovered that sturgeon key in on accelerating velocity during spawning and they spawn when water temperatures are warmer than 48 degrees Fahrenheit.
The U.S. Army Corps of Engineers has focused on high flows and temperature management at Libby Dam to help the recovery of the sturgeon. Since the sturgeon have not responded to these operations separately, the U.S. Army Corps of Engineers is required to release extra water this spring and for the next two springs per the 2006 U.S. Fish and Wildlife Service Biological Opinion. The Biological Opinion requires an extra 10,000 cfs (cubic feet per second) to be released during the peak spring flow for seven days. During that time, the water temperature needs to be favorable for spawning and there needs to be fish positioned above Ambush Rock (just downstream of Bonners Ferry) ready to swim upstream of Bonners Ferry.
The hypothesis is that the extra water released from Libby Dam will scour the sand from the cobbles and gravels for the spawning sturgeon and coax the sturgeon upstream to suitable spawning areas.
“This is a hypothesis that has been a long time coming,” says Jason Flory, Kootenai River Sturgeon Coordinator at the USFWS North Idaho Field Office. “It has been needed to be tested for 15 years. We will test the hypothesis and learn from it.”
“Let’s do this for three years, if we don’t get a response, we’ll move on to something else,” says Mick Shea, Libby Dam Project Manager.
The Kootenai Tribe of Idaho is already working on ‘something else’: habitat restoration. The Tribe completed their Kootenai River Habitat Restoration Project Master Plan in July 2009 with implementation to begin in the summer of 2011. The Master Plan addresses river morphology, aquatic habitat, riparian vegetation and river management in order to create a more resilient ecosystem that supports sturgeon and other aquatic species, such as bull trout, burbot and kokanee.
“The best chance is to restore habitat using a long-term, large-scale restoration program,” says Sue Ireland, Kootenai Tribe of Idaho Fish and Wildlife Department Director. “We don’t want a project that requires high flows.” The extra water released from Libby Dam will not come close to historic levels and for that reason additional flows may not be the answer, according to Ireland.
“The Kootenai Tribe is using an adaptive management approach to bring back ecosystem functions,” says Ireland. “We are trying to make sure we have the ability to be flexible.”
The first project will address stream bank erosion upstream of the Hideaway Island complex, which is downstream of the canyon reach. The project will utilize engineered wood structures to reduce the energy on the bank and change the inlet into the adjacent side channel to help create wetland habitat.
Future projects include establishing lower floodplain benches, regenerating riparian areas, creating wetland habitat and modifying channel shape. The restoration will be done within the confines of the dikes. Wetland habitat will be created by limiting flows into side channels and diverting that water into a deeper, mainstream channel.
While the Kootenai Tribe is working on habitat restoration, they are also prolonging the sturgeon population by raising juvenile sturgeon in their hatchery. Since the hatchery began operating in 1991, they have released 170,000 young sturgeon into the Kootenai River. Survival of the released sturgeon is 60 percent the first year and 90 percent the following years. Released sturgeon are helping overcome the bottleneck of fertile eggs not surviving.
To augment the population until eggs start surviving, hatchery technicians collect eggs and milt from sturgeon and raise the young. Technicians dutifully keep track of which sturgeon the eggs and milt are collected from in order to maintain genetic diversity in the population. The juveniles are also marked before they are released.
“The aquaculture program is preventing extinction,” says Ireland. Since females do not mature until they are 30 years old, the Kootenai Tribe is still waiting to see where they spawn. Even if the released sturgeon spawn in suitable substrate, the population will take a long time to rebound since sturgeon spawn once every five years.
With its late maturity, long reproductive cycle and hundred year life span, the sturgeon is slow to adapt to change. If it can adapt to the changes in the Kootenai River, then this ice age relic may see the next ice age.
Kootenai River photo courtesy Montana Department of Natural Resources.