July 25, 2019
Although a “lot” of sockeye salmon are passing Ice Harbor Dam, the first dam the fish encounter when migrating up the Snake River, few are passing upstream dams, according to Claire McGrath of NOAA Fisheries.
The expectation for the sockeye run this year is low, so the “lot” of sockeye McGrath referred to total just 299 fish at Ice Harbor, but passage at Lower Monumental Dam, the next dam upstream is far lower at 120 fish and that drops by more than half to 52 at Little Goose Dam and to 28 at Lower Granite Dam.
“We know the vast majority of the sockeye at Ice are mid-Columbia stocks,” McGrath told the interagency Technical Management Team at its meeting this week (July 25). She went on to say that there is very little data about the sockeye this year, with just two fish passing Ice Harbor that are identified by their PIT-tags, “but we do have some concerns that the fish are not passing the upstream dams at appropriate rates.”
“Relative to the 10-year average, this year is a very low return of sockeye, particularly Snake River sockeye,” she said.
The 10-year average for Ice Harbor passage by July 23 is 898 and last year the count was 347. Going upriver, the 10-year average passage at Lower Monumental is 1,022 and last year the count was 338. The 10-year average at Little Goose is 923 and last year it was 233. At Lower Granite, the 10-year average is 877 and last year’s count was 218.
Snake River sockeye salmon are listed as endangered under the federal Endangered Species Act. The preseason sockeye run size for the entire Columbia River basin was downgraded by one third to 62,800 fish based on the recent 5-year average run timing at Bonneville Dam. The preseason forecast was 94,400 fish. The U.S. v Oregon Technical Advisory Committee met July 8, downgrading the expected sockeye run (most of those sockeye will travel to mid-Columbia River tributaries, with few turning into the Snake River).
Fisheries managers, hoping to boost the number of fish passing Lower Monumental Dam, decided earlier this week to turn off the Adjustable Spillway Weir, which is designed to aid passage of juvenile salmon and steelhead.
There are criteria in the Fish Passage Plan for turning off the ASW at LoMo at this time of year, McGrath said. Among those criteria are the date – August 1 – or if flows drop to 35,000 cubic feet per second and stay there for at least three continuous days, a level the river is approaching now. TMT managers will meet again this Friday to determine if the ASW should remain off.
Much of the counting problem this year at lower Snake River dams has to do with the huge number of American shad passing through the Columbia River, with many turning into the Snake River. Some 7,447,091 shad had passed Bonneville Dam as of July 23, and 521,466 of those had passed Ice Harbor Dam, also as of July 23.
Some checks of fish counts are now in process at both McNary Dam on the Columbia River and at Ice Harbor. There have been some incorrect counts at Ice Harbor and those are being corrected, which will drop the number of sockeye passing that dam and will address the low conversion rate (the number of fish passing one dam that successfully pass the next upstream dam) between Ice and Lower Monumental, said Chris Peery, Corps Walla Walla District.
“Shad complicates it,” he said. “With piles of shad it’s easier to miss something.”
Jon Roberts of the U.S. Army Corps of Engineers said that cooler temperatures at Lower Granite have enabled the Corps to lower flows from Dworshak Dam, a source of cool water, on the Middle Fork of the Clearwater River. The Corps had been passing full powerhouse flows of about 9.4 kcfs, along with spilling water (totaling about 13 kcfs), to keep the tailwater at Lower Granite below 68 degrees Fahrenheit, partially as an aide to the few adult sockeye salmon expected to return to the Snake River and Sawtooth Basin this year. That is the upper temperature allowed in Lower Granite’s tailwater, according to NOAA’s 2019 federal Columbia River power system biological opinion.
Cooler weather is predicted and Roberts said the Corps would keep the outflow at Dworshak at full powerhouse for the foreseeable future.
In 2015, sockeye hit a thermal block as river temperatures rose considerably above the 68 degree F limit. Some 90 percent of sockeye died before reaching Ice Harbor Dam, the lower of the four Snake River dams. Idaho Fish and Game, NOAA Fisheries and the Nez Perce Tribes set up a rescue project at Lower Granite Dam to trap the adults and haul them to the hatchery at Eagle, Idaho.