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NW Fishletter #388, Dec. 3, 2018

[5] Council Seeks Review Of Region's Salmon-Predator Control Efforts

Scientists and economists will be evaluating the impacts and costs of birds, mammals and other fish that prey on listed salmon and steelhead in the Columbia Basin and the programs designed to control them, focusing on the region's most emergent threat: northern pike.

The Northwest Power and Conservation Council (NWPCC) voted Nov. 13 to seek a review by the Independent Science Advisory Board (ISAB) with the addition of one or two natural resource economists. They're also asking for an initial evaluation by May 2019 so findings can be considered alongside other recommendations to amend the Council's Fish and Wildlife Program, which is funded by the Bonneville Power Administration (BPA).

In its decision, the Council agreed to fund the review at between $80,000 and $150,000, and approved a draft letter to the ISAB with specific questions they'd like answered.

The Fish and Wildlife Program funds several projects to monitor, suppress and manage predators, ranging from hazing sea lions that snatch up adult fish at Bonneville Dam, to offering rewards to anglers who catch northern pikeminnow, a native fish that eats juvenile salmon on their way to the ocean.

In September, the Council provided additional funding to help a joint effort by the Colville and Spokane tribes and the Washington Department of Fish and Wildlife, who have been working to suppress northern pike, a large and voracious non-native predatory fish that has colonized the Columbia River in Lake Roosevelt, above Grand Coulee Dam.

"We seek an overall evaluation of predator impacts and predation management effectiveness in the Basin with a particular focus on piscivorous fish," the Council's letter to the ISAB states. "While conducting this review, we ask that the ISAB consider aspects and gaps within all areas of predation, including avian and marine mammal predation, which may need a deeper investigation during follow-up ISAB reports," it adds.

In addition to the scientific questions, the Council wants the initial review to address what information will be needed to assess economic impacts to natural resources if northern pike spread to the rest of the Columbia Basin--where they would begin preying on ESA-listed salmon and steelhead--as well as the potential costs of suppressing them.

NWPCC staffer Laura Robinson told the Council that while a review of all predators is needed, staff would like the ISAB to prioritize their time on predatory fish, especially given the current threats posed by northern pike. She reported that the Confederated Tribes of the Colville Reservation recently caught one near Grand Coulee Dam, much farther down the Columbia River and closer to the anadromous zone where they could then access the rest of the river through fish passage. "So, they're moving," she said.

The decision follows several presentations to the Council over the past few months on salmonid predators.

In November, The Kalispel Tribe outlined its successful efforts to slow the spread of northern pike, while staff from three mid-Columbia PUDs talked about their pikeminnow and Caspian tern programs. In September, an Oregon State University professor outlined a long-term effort to reduce Caspian tern numbers in the Columbia River estuary. And on Nov. 13--just prior to the decision to approve a review of predation--the Council heard from the U.S. Army Corps of Engineers about its role in managing predators in the Columbia Basin.

Tim Dykstra, the Corps' senior fish program manager, outlined the agency's management plans to control Caspian terns and double-crested cormorants in the Columbia River estuary, as well as its management plan for Caspian terns at inland locations near the Columbia and Snake rivers.

He said the agency also supports efforts by Washington, Oregon and tribes to manage California sea lions by monitoring and providing access at Bonneville Dam, where the larger Steller sea lions have recently become the more numerous problem after states began hazing, relocating, and sometimes euthanizing California sea lions. "The Corps is in a supporting role," Dykstra told the Council.

Dykstra said the Corps will continue to implement its three management plans for predator birds, and to monitor sea lions at Bonneville Dam, but has no plans for additional predator management until the Columbia River System environmental impact statement is complete.

He outlined successes so far in managing Caspian terns in the estuary.

In the 1990s, the Caspian tern population on Rice Island in the Columbia River estuary was believed to be the world's largest, at about 9,000 breeding pairs, Dykstra told the Council. He said salmon and steelhead from the Columbia Basin comprised about 83 percent of their diet.

The Corps first implemented a plan to convince the terns to move their nesting site from Rice Island to East Sand Island, which is still in the estuary but much closer to the Pacific Ocean in hopes that the birds would "diversify their diets." By 2001, the breeding pairs had nearly all relocated their nesting sites to East Sand Island, and studies found they reduced their consumption of Columbia Basin salmonids to about one-third of their diet.

The Corps then developed new nesting sites on their migration path, from San Francisco Bay to southern Oregon, where many of the terns now nest, he said. At the same time, the agency reduced the size of suitable nesting on East Sand Island from six acres to one acre, with a goal of reducing breeding pairs to about 3,125.

The agency came close to reaching that goal in 2017, when some 3,500 pairs nested on East Sand Island, but their numbers bounced back this year when around 5,000 pairs unexpectedly squeezed into the reduced habitat.

Dykstra told the Council that it's premature to determine that they need to further reduce the size of the island's nesting site, and noted it would require a supplemental environmental impact statement. And success of the program has been notable, he said. In 2006, the terns were consuming more than one out of six juvenile steelhead in the estuary, while by 2017 that dropped to one in twenty, he noted.

Dykstra also reported success controlling double crested cormorants on the island, where management actions began in 2015. He said the management plan included killing almost 5,600 cormorants, and destroying about 6,000 nests between 2015 and 2017.

He said the colony abandoned the island in 2017, but agency officials believe that was thanks to some "opportunistic eagles" that preyed on the birds. Breeding pairs dropped from more than 12,000 in 2015 to fewer than 4,000 in 2018.

Farther up the Columbia River, the Corps also manages Caspian tern colonies on Goose and Crescent islands, where the birds were consuming almost 16 percent of upper Columbia juvenile steelhead, and nearly 4 percent of juvenile steelhead from the Snake River, Dykstra said. Using the same approach used on Rice Island--attracting the terns to other nesting sites--those numbers have been reduced to fewer than 0.1 percent, he said.

He noted that the agency has also installed a series of wires at all of its dams, called avian arrays, that make it difficult for birds to dive in the water and pick off juveniles that are disoriented from migrating through the project. -K.C. Mehaffey

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Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: K.C. Mehaffey
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