REDDING, California – For the second year in a row, drought conditions have killed nearly all young winter-run Chinook salmon in the Sacramento River, federal officials said Wednesday.
Higher water temperatures coming out of Shasta and Keswick dams has been fatal to more than 95 percent of the endangered winter-run eggs and recent hatches, an official with the National Oceanic and Atmospheric Administration said.
“There is a real risk of extinction for this species. They are real vulnerable to water temperatures,” said Maria Rea, the agency’s assistant regional administrator.
NOAA and the U.S. Fish and Wildlife Service count young winter-run salmon in the river at Red Bluff as they migrate downstream to the ocean. This year the number of salmon that have been counted is 22 percent lower than at this time last year, she said.
Federal and state officials estimate that 95 percent of the young winter run were killed mainly by higher temperatures in the river, she said.
State and federal officials cut back the amount of water released from the dams throughout the summer to prevent a winter-run die-off in the fall. So far that effort has not paid off, officials said.
“Again, it was a high risk plan because it did expose the eggs to higher temperatures than we would like,” Rea said.
Using a temperature control curtain installed on the back of Shasta Dam, U.S. Bureau of Reclamation operators can control at what elevation they take water from the lake. Salmon eggs begin to die off in temperatures above 56 degrees.
In 2014, the lake’s cold water pool was exhausted by fall, leaving higher water temperatures going down the Sacramento River, killing an estimated 95 percent of the eggs and recent hatches, officials said.
Bureau officials have blamed the lack of rain and snow on the low water level in the lake.
“When Shasta reservoir is very low, there is limited cold water,” Rea said.
So this year, beginning in late spring, the bureau and state Water Resources Control Board decided to reduce dam releases to preserve the pool of cold water in the lake and save it for the fall.
Rea said temperatures in the river this past summer averaged 57 degrees and at times 58 degrees.
She said the number of winter-run salmon going downstream could increase between now and the end of the year. There could still be many more fish that have not started downstream, she said. The salmon are prompted to swim downstream during rains that increase flows in the river.
Last year, there were some fall rains and higher flows in the river that moved more fish downstream past the counting traps in the river, said Clark Blanchard, a spokesman for the California Department of Fish and Wildlife.
“This year, there has not been any flow or turbidity events that we would expect to trigger winter-run juvenile migration from the upper river,” Blanchard said. “Migration timing of juvenile winter-run varies considerably between years.”
There are four runs of salmon in the river — fall, late fall, winter and spring — each named after the time of year when adults returning upstream to spawn swim under the Golden Gate Bridge.
Last year, state fish and wildlife officials closed to all fishing a 4 1/2-mile section of the Sacramento River in Redding to protect spawning winter-run salmon.
Blanchard said the state is watching what is happening with the salmon but hasn’t decided whether it will take similar action next year.
John McManus, executive director of the Golden Gate Salmon Association, said the commercial and recreational salmon fishing in the ocean was restricted this year because of the low winter-run numbers.
“It’s starting to look like we’re seeing a repeat of last year,” McManus said.
McManus said he is concerned the same fate awaits the fall-run Chinook, the largest of the runs.
In a letter to State Sen. Mike McGuire, DFW Director Charlton Bonham estimated 95 percent to 98 percent of the young fall-run salmon died due to high water temperatures.
McManus said the fall run is especially worrisome because those are the fish the commercial fishing industry depends on.
Rea said the U.S. Fish and Wildlife Service is raising more winter-run salmon at the Livingston Stone Hatchery near Shasta Dam to ensure survival of the species. She said there are about 440,000 young salmon at the hatchery.
Last winter, the hatchery released more winter-run Chinook to offset the losses in 2014. Rea said they haven’t decided whether to do that again in 2016.
NOAA and other federal agencies are also considering a plan to within the next couple years truck winter-run salmon around the dams and plant them in the McCloud and Sacramento rivers upstream of Lake Shasta.
Before Shasta Dam was built, the winter run migrated up into those rivers to spawn, but the dam blocks the fish from getting up into those areas.
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