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Sockeye Returns to the Snake River are on the Rise Again, Possibly Because of Improved Ocean Conditions by Eric Barker Spokesman-Review, July 25, 2021

"The last couple of years the fish size has been smaller."

Snake River sockeye are in the midst of posting one of their best returns in several years and doing it during some of the toughest conditions seen since 2015.

But how well the 2021 return ultimately performs is likely to rely both on extraordinary intervention from human beings and the ability of the fish to tolerate prolonged exposure to elevated water temperature.

Through Wednesday, 533 sockeye had been counted at Lower Granite Dam. That is just under the 10-year average of 574 and the highest return since 2016, when 730 sockeye had been counted passing the dam as of July 20.

The Idaho Department of Fish and Game recently estimated more than 1,400 sockeye bound for the Snake River had passed Bonneville Dam as of last week. That is nearly double the preseason forecast. As of Thursday, no sockeye had been trapped in the Stanley Basin, some 900 miles from the Pacific Ocean.

The department and other fisheries agencies are attempting to trap returning sockeye at Lower Granite Dam, remove them from the river and take them to hatcheries by truck. Temperatures in parts of the lower Snake and Salmon rivers have reached well into the 70s at times this summer, a level considered dangerous and perhaps deadly to the fish. As of Thursday, 149 of the sockeye that had been counted at the dam had been trapped and loaded on trucks.

What does it mean?

There is some indication that ocean conditions have improved, at least incrementally. Dan Baker, manager of the state's Eagle Fish Hatchery, said this year's returning adult sockeye appear to have done well in salt water.

"Fish size is more normal than what we have seen in the (recent) past," Baker said. "The last couple of years the fish size has been smaller."

Hatchery managers at the Idaho Department of Fish and Game said they believe changes they made to the smolt release protocol have led to higher survival of young fish.

"We are hopeful things are turning around a little bit," Baker said.

Fish on the brink

Sockeye salmon are Idaho's most imperiled anadromous fish. They were protected under the Endangered Species Act in 1991 after struggling for decades. Only four adult fish returned to the Sawtooth Basin in 1991, and just one fish, nicknamed Lonesome Larry, returned in 1992. Only 23 sockeye returned to the basin in the 1990s, which included two years when no fish made the journey.

After Snake River sockeye were listed, the state and federal governments and the Shoshone-Bannock Tribes started a captive broodstock program in which many of the fish and their offspring were kept in a hatchery for their entire lives.

The rescue program helped keep the fish from going extinct and, when combined with improved ocean and river conditions, led to some higher returns. Some sockeye are now allowed to spawn in Redfish, Alturas and Petitt lakes.

The run peaked at 2,786 in 2014, but that was the last time it broke 1,000 fish at Lower Granite Dam. Just 81 sockeye returned in 2019. That jumped to 640 last year. Fish that make it to the dam still have hundreds of miles to go to reach spawning grounds.

In 2013, the state opened its Springfield Hatchery where about 1 million sockeye smolts are produced and released each year. Those fish initially suffered poor survival rates upon release, but agency officials said they believe they have mitigated water quality conditions responsible for the higher-than-expected mortality.

If ocean conditions are on the rise and survival of juvenile fish upon release increases, Idaho could see higher returns in the future. But there is reason to worry. Federal fisheries scientists predict the fish will be hit hard by climate change and could see already low survival rates plunge by 80%. They wrote that climate change will lead to warming river temperatures and reduced flows that will make it tough for adult sockeye to survive their 900-mile journey from the ocean to spawning grounds.

Those conditions played out in 2015 when low flows and high temperatures wiped out most of the Snake and Columbia river sockeye runs.

Similar but thus far less extreme conditions have been observed this summer. Reduced river flows and an extreme heat wave in late June and early July spiked water temperatures both in the Snake and Columbia River hydropower system and in the Snake and Salmon rivers upstream of the dams.

State, tribal and federal fish and water managers have made several tweaks at the dams in an attempt to keep water cool, including an early start to flow augmentation from Dworshak Reservoir. Those moves appear to have been somewhat successful at keeping river temperatures beneath Lower Granite Dam from spiking to dangerous levels. But temperatures at other dams have climbed above 70 degrees, and the water has been even hotter above the hydropower system, making it unclear how many of the fish that made it to Lower Granite Dam, but were not trapped, will survive the rest of their journey. River temperatures receded from highs recorded during the heat wave.

"We are still counting on some of those to come all the way on their own," Baker said. "The first fish to cross Granite was on the 24th of June. Under normal or good conditions, those first ones are about 30 to 35 days (out), so within a week or in the next two weeks we should start to see fish arrive in the basin."

Related Pages:
Sockeye to be Trucked to Redfish Lake by Associated Press, Challis Messenger, 7/8/21
'This is Worse' than 2015: Northwest Weather Heats Rivers, Puts Idaho Sockeye in Danger by Rocky Barker, Big Country News, 7/4/21
A Truck-assisted Migration: Salmon Smolts Get a Helping Hand to Reach Coast Amid Severe Drought by Harry Morse, Idaho State Journal, 6/16/21
Pacific Northwest Heat Wave Sets Up 'Grim' Migration for Salmon by Lynda Mapes, Northern New York 360, 7/1/21
'This is Worse' than 2015: Northwest Weather Heats Rivers, Puts Idaho Sockeye in Danger by Rocky Barker, Big Country News, 7/4/21
Count the Fish, 1977-2014, Salmon Recovery Effortsby GAO