Anchovies Likely Gave Steelhead a Boost in the Nisqually

A population boom of anchovies three years ago may have saved Nisqually juvenile salmon from getting eaten by seals. A resurgent run of more than 2,000 steelhead returned this spring.

“One of the things we’re assuming about the limitations of steelhead survival is that they’re preyed on by marine mammals, like harbor seals, when they’re leaving as juveniles,” said David Troutt, natural resource director for the Nisqually Tribe. “But when seals have another food source like anchovies available, it seems like the steelhead can sneak through.”

The Nisqually Tribe is keeping tabs on the steelhead run with spawning surveys and a camera at a fish ladder.

“One of our goals is for 2,000 steelhead to come back every year for the run to be self-sustaining and building back to a harvestable run like it used to be when it numbered over 8,000,” Troutt said. “While we know this is likely just a one-year spike, it means we’re heading in the right direction.”

The tribe is a partner in the Salish Sea Marine Survival Project, which gauges steelhead survival. They use an array of receivers across Puget Sound that follow outgoing juvenile steelhead fitted with audio tags.

“It’s clear that the biggest problem facing steelhead in Puget Sound is from seals and sea lions,” Troutt said. “Our most recent highest measured survival of juvenile steelhead through Puget Sound have when something happened to change seal and sea lion behavior.”

A few years ago the tribe also tracked the impact of a pod of transient orcas upon their arrival in Puget Sound, using funds they raised for that purpose. “It turned out, we were right, we saw many more steelhead make it out of Puget Sound because the seals and sea lions were chased away by orcas,’ Troutt said.

The Nisqually steelhead population crashed almost 20 years ago from as many as 9,000 to fewer than 1,000. Puget Sound steelhead were listed under the federal Endangered Species Act in 2007.

“We have not fished for steelhead for years because their numbers could not sustain harvest,” said Farron McCloud, Nisqually tribal chair. “We hope that our sacrifice will help this run come back.”

Decades of freshwater habitat restoration and protection by the tribe and its partners has helped temper the decline of the run.

“The reason we have Nisqually steelhead returning at all is because we’ve worked hard to bring back a lot of habitat,” Troutt said. “They can hold on during bad years and then take advantage of good years.”

Salmon habitat throughout Puget Sound is faring much worse. “Shoreline armoring – things like bulkheads – is increasing despite decreasing runs and endangered species listings,” Troutt said. “We know that 40 percent of Puget Sound is modified and that more than a quarter is armored.” Armoring decreases the amount of food available to salmon and makes it more likely predators will eat them.

A juvenile steelhead being weighed before it is fitted with an accoustic tag in 2015. Photo: Emmett O’Connell