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NW Fishletter #372, August 7, 2017

[6] Northern Pike Now 40 Miles Farther Downstream in Lake Roosevelt

Northern pike have spread another 40 miles farther downstream in Lake Roosevelt, even though a program managed by the Spokane and Colville tribes and Washington Department of Fish and Wildlife has removed thousands of the invasive fish from the lake.

Representatives of the three Lake Roosevelt co-managers briefed the Northwest Power and Conservation Council July 12 on their work to suppress this predatory species. Lake Roosevelt is the reservoir behind Grand Coulee Dam.

This year alone, over 1,080 northern pike have been removed from the reservoir.

That's almost the same number of adult northern pike captured from the lake in 2015 and 2016 combined, Holly McLellan, fish biologist with the Confederated Tribes of the Colville Reservation, told NW Fishletter of the reason for the higher numbers this year is a bigger removal effort, with more nets deployed to capture the invasive fish.

The majority of captured northern pike have been taken near the Kettle River mouth, Singers Bay and the Colville River. The new downstream discovery occurred near Hunters, Wash.

Northern pike are a threat to the Columbia Basin's native fish species because they can prey on any fish that is less than 75 percent of their body size, McLellan told the Council. The only fish--native or nonnative--safe from pike predation are adult white sturgeon.

A 26-pound female northern pike was taken from Lake Roosevelt in June, the largest one caught since the removal program began, McLellan said.

pike
A 26 pound Northern Pike caught in 2017. Credit: Colville Tribes.

Salmon managers throughout the basin are worried that the predacious pike could invade the river system below Chief Joseph Dam, where anadromous salmon and steelhead spawn.

They have already disrupted ecosystems in Alaska, California, Colorado, Idaho, Montana, Utah and Washington.

Northern pike eradicated native salmonids in Alaska's Sustina River watershed in the late 1990s, and eliminated multiple minnow species in Montana in the early 2000s, the managers told the Council. Currently, they added, northern pike are preying on west slope cutthroat trout and bull trout in Montana 's upper Flathead River.

Northern pike were first discovered in the upper reaches of the Columbia River in Lake Roosevelt in 2011. Prior to 2014, their numbers were thought to be few, but a 2015 pilot study showed an increasing population.

Since then, numerous parties--including the PUDs of Chelan and Grant counties, the Colville and Spokane tribes, and BPA--have been paying for efforts to reduce the quantity and distribution of the fish.

In June the Spokane Tribe asked the Council for $123,000 to expand its pike-removal work in the lake. BPA and the Council's Budget Oversight Group is considering the request.

An Independent Scientific Review Panel evaluation of the request said the scientists were not surprised that further suppression efforts were needed, as they had previously questioned whether the current removal program would be sufficient to control the spread of northern pike in Lake Roosevelt.

The ISRP called for the Spokane and Colville tribes, WDFW, BPA and the Council to develop a broader strategy to control northern pike in Lake Roosevelt. The July presentation to the Council by the tribal and state co-managers responded to that guidance, describing how the data they are collecting and the new tools they are developing will help inform longer-term strategy. -Laura Berg

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NW Fishletter is produced by Energy NewsData.
Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: Laura Berg
Phone: (206) 285-4848 Fax: (206) 281-8035

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