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Heat Wave Could Be Hard On Fish

by Eric Barker
Lewiston Tribune, June 26, 2021

An adult sockeye salmon photographed in the Columbia River near Drano Lake in Washington in July of 2015 covered in fungus caused by thermal stress. (USGS photo) Columbia Basin fisheries managers worry the approaching heat wave could hammer endangered Snake River sockeye and have cascading effects on other species of protected salmon.

The lower Snake and Columbia rivers are quickly warming and fisheries managers fear a repeat of 2015 when most of the sockeye run melted away as it progressed upriver -- the victim of water temperatures in Columbia and Snake river reservoirs that reached lethal levels for the fish.

State, tribal and federal officials have already implemented the few tools they have to mitigate rising water temperatures in the lower Snake River. Earlier this week, they began releasing 42-degree water from Dworshak Reservoir. It will take three to four days for the water to reach Lower Granite Dam on the Snake River, where official policy aims to keep water at or below 68 degrees.

The fisheries and dam managers also fired up pumps at Lower Granite and Little Goose dams that raise cooler water from deeper areas in front of the dams and directs it to fish ladders. The ladders typically draw warmer surface water, and in heat waves, it can reach levels high enough that migrating salmon are reluctant to use them.

"In my opinion, we really don't have a lot of options that will make a big difference," said Charles Merrill of the Washington Department of Fish and Wildlife and a member of the Fish Passage Advisory Committee, a regional group of fisheries and water managers. "We only have so much water in Dworshak and this heat wave is going to pull out most of the water that would (normally) sustain cool water temper management through the end of August."

His comment illustrates the fact many temperature mitigating actions carry pros and cons. While the early application of Dworshak water may help avert a potential disaster for sockeye salmon, it could also carry consequences for fall chinook and steelhead later this summer.

The water releases began Tuesday when the reservoir was still 3 feet shy of refilling. In most years, the cool water releases start after the Fourth of July holiday and run through mid-September. Over the roughly 2-1/2 months, the reservoir is lowered 80 feet.

Starting before the reservoir reached full pool means there will be less water available for the cooling operation. Starting about 10 days to two weeks early means what water is available will be exhausted sooner -- in early-to-mid-August, when adult fall chinook and some steelhead are moving upriver. Without the cooling effect of the Dworshak water, those runs could stall or the fish could suffer from river temperatures in the 70s.

Becky Johnson, production director of the Nez Perce Tribe's Department of Fisheries Resources Management, called it a potential "heartbreaker."

"We have worked so hard to build that population up," she said of the Snake River fall chinook run.

Also at risk are wild spring and summer chinook that are biding their time in tributaries to the Snake River before spawning in August and September. The current heat wave could spike stream temperatures for those fish.

"It's hot out there and there is not a lot of water," said David Johnson, director of the tribe's Department of Fisheries Resources Management. "It does not bode well for these fish and there are precious few fish out there."

Low flows and water temperatures approaching 70 degrees on the South Fork of the Salmon River prompted the tribe and Idaho Fish and Game to move returning hatchery chinook from a holding facility there to Rapid River Hatchery.

Fisheries officials in Idaho and the National Oceanic and Atmospheric Administration are considering intercepting adult sockeye at Lower Granite and Ice Harbor dams and trucking them upriver to the Stanley Basin to be held at the Sawtooth Hatchery. Sockeye enter the Columbia River and push upstream in June and July, exposing them to potentially dangerous temperatures.

"They have poor timing relative to these heat waves," said Jonathan Ebel, a fisheries biologist with the Idaho Department of Fish and Game at Boise.

Members of the Fish Passage Advisory Committee have even brainstormed "out of the box" hypothetical actions that might help reduce water temperatures, but admit they are unlikely to be implemented without a long and rigorous review process that would last well beyond the pending emergency. Those actions include things like drafting reservoirs on the Snake River to levels that would temporarily halt barge transportation; periodically opening locks to allow easier passage for returning adult sockeye; running Snake River reservoirs at lower levels, known as minimum operating pool, that would hamper but not halt barge transportation; reducing or altering spill regimes at some dams to reduce mixing of the cold Dworshak water with warmer Snake River water; or changing their target temperature in the lower Snake River from 69 to 70 degrees in an effort to stretch out the Dworshak water.

Ebel said the ideas were generated more as a thinking exercise than actions that could be implemented quickly.

"It just shows we need a long-term temperature plan as we see these hot years more often," he said. "We've got to think out of the box in the long term."

Eric Barker
Heat Wave Could Be Hard On Fish
Lewiston Tribune, June 26, 2021

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