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Idaho Department of Fish and Game

Summer steelhead returns are off to a dismal start in 2017, with 75 percent fewer fish than usual crossing Bonneville Dam so far this season.

The latest research suggests a big part of the recent population decline may be tied to factors soon after juvenile steelhead enter the ocean, such as predation, parasites and industrial contamination.

A study published June 26 in the Canadian Journal of Fisheries and Aquatic Sciences takes a closer look at Pacific Northwest steelhead runs from the lower Columbia River and Puget Sound, tracking the survival of smolts early in their ocean life.

Neala Kendall, research scientist and project leader with the Washington Department of Fish and Wildlife in Olympia, said the study did not specifically examine upper Columbia steelhead, though ocean conditions apply to all fish runs.

“This is important for interior Columbia River steelhead,” Kendall said. “They are experiencing the same ocean as lower Columbia River steelhead, certainly.”

The publication comes at a time when fisheries managers across the Columbia Basin are projecting the lowest steelhead returns in 37 years. According to data, just 4,075 steelhead have passed Bonneville Dam since July 1, compared to 16,996 at the same time last year. The five-year average to date is 19,272.

Fisheries managers in Oregon and Washington have approved steelhead restrictions on the Columbia River, closing steelhead retention below The Dalles Dam for the entire month of August. Steelhead retention is closed between The Dalles and John Day dams during the month of September, and from John Day Dam to the Oregon-Washington border during October and November.

Juvenile steelhead already face an arduous journey migrating from the upper Columbia and lower Snake rivers. Once they finally reach the ocean, Kendall said conditions right away play a significant role in determining total marine survival.

The study was launched in 2013 as part of the Salish Sea Marine Survival Project, a collaboration of both U.S. and Canadian scientists. Kendall said the team analyzed 35 coastal steelhead runs dating back to the late 1970s, primarily from Puget Sound and lower Columbia River.

“From our research, it’s conditions in the early ocean life of steelhead, shortly after they hit saltwater, that influence their total marine survival,” Kendall said. “They all go to the same place in the ocean. That doesn’t seem to matter.”

In particular, Kendall said harbor seals, harbor porpoises and birds seem to be preying more on juvenile steelhead due to a reduction in populations of forage fish, like herring, anchovies and eulachon.

Every year since the project began, Kendall said researchers have released between 100-200 tagged steelhead smolts into the Green and Nisqually rivers — which flow into Washington’s Puget Sound — to measure predation by seals. One year, just 6 percent of the tagged fish made it out of the Sound. Another year, the total was 40 percent, which just so happened to coincide with a huge anchovy boom.

“I think this research looking at predation is going to be important,” she said. “The same predation is taking place down in the Columbia River on both juveniles and adult (fish).”

Other parts of the study focus on migrating fish that have been infected by nanophyetus, a parasite that burrows into juvenile salmon and steelhead and attacks their muscle tissue.

Kendall said nanophyetus has been documented much more heavily in the southern Puget Sound, though there is concern that the parasite could spread as waters continue to warm. During the 2015 drought, Kendall said the team documented nearly 100 percent of steelhead with nanophyetus in the Nisqually River.

River contaminants are another concern, with Kendall mentioning polybrominated diphenyl ethers, or PBDEs, a compound found in flame retardants.

“There are certain levels if they get into fish and other animals that can affect their health and vitality,” she said.

All of those factors have contributed to a decline in Northwest steelhead survival over the past four decades, Kendall said. Populations that once saw 10 percent returns are now down to 5-6 percent. Columbia River steelhead have fared slightly better than Puget Sound steelhead, she added.

Kendall said they are working with the state of Washington to fund their program for the next two years, which will allow them to continue refining their data.

“Hopefully, we can make better policy and management recommendations,” she said.

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Contact George Plaven at gplaven@eastoregonian.com or 541-966-0825.

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