by Michael McLaskey
The Kootenai River white sturgeon (KRWS) is still an endangered species, according to the U.S. Fish & Wildlife Service (FWS). It was listed in 1994, and there may be as few as 500 remaining in the river system.
KRWS is related to the Columbian white sturgeon, but to find those genetic similarities, one would have to go back 10,000 years or more to the last ice age when they were isolated from the rest of the Columbian population. The Kootenai River white sturgeon can be found upstream to Kootenai Falls in Montana, and downstream through Kootenay Lake in B.C. to the Cora Linn Dam.
One of the many factors inhibiting the recovery of KRWS could be that the Kootenai River has changed since the Libby Dam in Montana was built in 1975. Prior to the dam, the average spring runoff ran from 60,000-80,000 cubic feet per second. “That flow has been cut in half,” according to Jason Flory, biologist with FWS and recovery coordinator for KRWS.
“That’s a complete change in flow regime,” Flory said. “It was reduced to a much smaller river system, and the temperature regime has changed as well.” He explained that increased flows during the winter, dikes along the river, increased erosion and subsequent loss of riparian habitat are all results of the dam.
The biggest issue perhaps facing the KRWS is their spawning habits. White sturgeon can live to be more than 100 years and don’t even reach sexual maturity until they’re about 30. Biologists such as Flory and others have noted that the section of the river that KRWS spawns in produces zero recruitment (survivability) for their hatched young.
Flory explained that if this was caused by predation, “We’d still expect to see a small bump in survival.” He said the river bottom composition in this section is primarily mud and silt, which is bad for newly-hatched fries.
KRWS are broadcast spawners, meaning they release their eggs and sperm into the water column, and when they meet, the fertilized eggs will ideally latch onto a rock or gravel.
Why are the KRWS spawning in an area characterized as mud-and-silt? “That’s the million dollar question,” said Flory. “It could be that the older fish lack the bio-energetics to swim upstream where there are more hospitable spawning grounds, or there could be some kind of barrier in the river system that prevents them from going there.”
Enter the Kootenai Tribe of Idaho’s (KTI) Conservation Aquaculture Facility. Operating since 1990, the hatchery is currently all that’s preventing sturgeon from becoming extinct.
According to Susan Ireland, Fish and Wildlife Department director for the Kootenai Tribe of Idaho, there are nine sites where one-to-two-year-old fish are released. The hatchery releases 5,000-15,000 juveniles every fall, and this year, they’re releasing 500,000 larval sturgeon at a few key sites where the recovery team thinks they will imprint well.
In the past, KTOI tried releasing more small fish, but they noticed an extremely low survivability. Now they release fewer fish, and the larger fish have a 90 percent survivability rate.
This endangered species will remain listed until several successful spawning events in the wild provide enough genetic diversity to guarantee the long-term survival of the species. Flory said, “If we get everything in place to where they start reproducing naturally, they should be fine, genetically speaking.”