Sturgeon spill tests end in failure
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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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