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Sturgeon spill tests end in failure

December 7, 2012
A controversial experiment affecting northwest Montana and northernmost Idaho has ended by legal edict after failed attempts -- using large surges of water -- to draw white sturgeon farther up the Kootenai River to the most desirable spawning habitat.

The experiment involved sending as much 35,000 cubic feet of water gushing out of northwest Montana’s Libby Dam with timing aimed to coincide with Kootenai River white sturgeons’ urge to spawn. That maximum volume was to include full power house capacity and as much as 10 kcfs through spill gates.

The idea was to mimic as closely the springtime peak runoff the sturgeon experienced before the dam was built. Flows have been manipulated by the dam’s operations for power production and flood control since the early 1970s.

According to research documents there has been an overall decline in recruitment of wild sturgeon into the spawning population beginning in the 1950s with an almost total absence of recruitment after 1974.

A variety of factors could have affected the sturgeon population, which now includes an estimated 1,000 wild adult fish. Those other changes that could have affected sturgeon recruitment include the construction of dikes on natural levees, changes in the level of Kootenay Lake and in backwater conditions near Bonners Ferry, loss of wetlands in the river valley, and reduction of the river’s nutrient load, and over fishing.

The decline of a white sturgeon population resulting in a 1994 U.S. Fish and Wildlife Service listing of the species as endangered under the Endangered Species Act. Kootenai white sturgeon occur in Idaho, Montana and British Columbia and are restricted to approximately 167.7 river miles from Montana’s Kootenai Falls, located RM 31 below Libby Dam, downstream through British Columbia’s Kootenay Lake to Corra Linn Dam at the outflow from Kootenay Lake.

“The intent was to coax the sturgeon to migrate upstream to spawn” the USFWS’s Jason Flory said of a plan that was rooted in the federal agency’s 2006 ESA biological opinion regarding Libby Dam impacts on listed species in the Kootenai River drainage.

After test periods utilizing varying amounts of spill in 2010-2012 “it doesn’t look like we achieved” the intended results, Flory said. There were no detectable change in Kootenai sturgeon migration and spawning behaviors.

Researchers monitoring the big, long-lived fish, which on average don’t reach reproductive maturity until about age 30, did not note any spawning activity in any of the three years in the “braided” reach upstream of Bonners Ferry, Idaho. That cobble and gravel-bottomed stretch of the river is believed to be the most suitable but is little used. The white sturgeon now primarily spawn with little success in silt-filled gravel downstream.

The big flush experiment was triggered by a 2008 agreement that settled a lawsuit challenging the USFWS 2006 strategy for assuring that dam operations did not jeopardize the survival of white sturgeon population. BiOps can outline mitigation actions aimed at improving conditions for listed fish.

The white sturgeon BiOp prescribed enhanced outflows through the turbines during the late spring sturgeon spawning period, with those flows supercharged with spill in three of the 10 years of the life of the document. The settlement agreement reached with the plaintiffs, the Center for Biological Diversity, called for the spill tests to be implemented, if conditions allowed, if the non-spill pulse tests produced none of the intended results. The USFWS judged that non-spill pulse operation did not satisfy settlement agreement requirements in 2008 and 2009, so the spill experiment was launched.

“If you have a hypothesis you need to test it,” Flory said of scientific processes. The spill pulse does not seem to have met the test.

“We’re still going to have a pulse” as called for in the 10-year BiOp, Flory said. “But it’s not going to be managed through spill.”

“We’re looking at different ways to use it,” Flory said of the BiOp-mandated spill. The document called for a tiered approach with a certain volume dedicated for release during the sturgeon spawning period. That volume changes from year to year depending on the available water supply.

Flory said that the USFWS is now working with state and tribal co-managers and other members of the Kootenai Sturgeon Recovery Team to develop an updated approach to managing the sturgeon pulse.

“Three times – it’s over,” Brian Marotz of the Montana Department of Fish, Wildlife and Parks said Wednesday during a TMT year-end review of operations. The state of Montana, and MDFWP, has been critical of the spill operations. The cascading water stirs up “total dissolved gas” in the river below that can be harmful to resident fish such as bull trout.

Also, the spill program had few fans among the residents of the Kootenai Valley’s lowland up and downriver from Bonners Ferry, whose croplands become saturated, in some cases flooded. The Kootenai River is nearly 450 miles long. Beginning in British Columbia, Canada, the river flows through Montana and Idaho, and then turns northwest back into British Columbia

During Wednesday’s TMT meeting Marotz pointed out that gas super-saturation measurements this past year exceeded Montana’s 110 percent for 41 days, including during on-again, off-again sturgeon spill during a two-week period in June.

The Corps, which operates Libby Dam, was also forced to evacuate water when record June precipitation caused the largest inflow volume to Libby during the spring and summer since the dam was built. High rainfall totals caused the reservoir and river to rise rapidly, resulting in a flood control operation through July 11.

“Gas bubble trauma was observed in Kootenai River fish, but we did not document a large fish kill or evidence of lasting impacts, which came as a pleasant surprise since spill produced extended exposure to high gas saturation levels,” Marotz said.

“That said, we won’t have a clear picture of what fisheries impacts occurred for several years, as annual data accumulate” from ongoing PIT tag research, Marotz said.

“Fish survival apparently decreased during the last extended spill in 2006,” he said. Details from that research was not statistically significant given the small number of PIT tags deployed. But more tags have been deployed since.

“Analysis of the 2012 spill will be based on many more data points, so we’ll be able to document impacts, in any occurred, within a few years,” Marotz said.

Biologists start seeing gas bubble trauma in fish after they’ve been exposed to TDG of 110 percent or more for 11 days, or more immediately if TDG rises above 122 percent. This year the peak was 129.4 percent.
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