Fishery biologists with a Seattle-area tribe are capturing a new predator species in Lakes Washington and Sammamish to monitor their movements and whether they cross paths with salmon.
It’s unclear how many of the illegally introduced fish are actually in the system, but concern is building and the Muckleshoot Tribe reports they have “successfully tagged and released multiple walleye” already this year.
A request for comment from the tribe had not yet been returned as of this writing, but details of the operation come from the LOAF, or list of agreed-to fisheries that was signed by WDFW and the Northwest Indian Fisheries Commission earlier this month as the parties reached an agreement at North of Falcon, and which was posted last week by the state agency.
Besides outlining all the treaty, commercial and recreational salmon fisheries over the coming 12 months, the 105-page document includes the Muckleshoot’s aims and methods for their two-year warmwater species study in the Lake Washington basin.
The tribe says it wants to catch up to 15 walleye to “assess their overlap with migrating juvenile salmonids in addition to locating areas these invasive predators may be targeted in subsequent fisheries.”
Tribal fishers are targeting one of seven zones in Washington and Sammamish at a time, using up to eight 300-foot-long gillnets with 31/2- to 6-inch mesh. The nets fish during the work week and are closely monitored to reduce the possibility of snagging the few if any ESA-listed steelhead in the basin.
Walleye are being implanted with acoustic devices that can be read by receivers stationed around the lakes that are otherwise used to track tagged returning adult Chinook and sockeye and young outmigrating coho.
Overlapping walleye movements with the coho will help model their potential to cross paths with Endangered Species Act-listed Chinook smolts.
The Muckleshoots say their effort “will benefit salmonid management in the Lake Washington basin,” as well as inform researchers on walleye diets and distribution.
Of note, a “second consideration” is to figure out if catch rates on walleye and bass are “high enough to result in an economically viable fishery … Data collected will inform managers of areas and times that a tribal net fishery could be economically viable as well as areas to avoid/target minimizing bycatch and optimizing harvest.”
According to plans, gear, locations and effort may be shared with the National Oceanic and Atmospheric Administration, along with details on any steelhead or Chinook caught, with the test fishery being shut down after a third and fifth of each species is encountered.
Walleye first turned up in Lake Washington in 2005, a small male, caught by University of Washington researchers, with anglers catching one or two in following years.
But in 2015, state and tribal biologists caught a dozen, mostly in Lake Washington between Mercer Island and Bellevue, including a 13.5-pound hen that was dripping eggs.
As the species is native to waters east of the Rockies, the only way they could have arrived in the urban lakes is in livewells. The nearest source populations are about 120 miles east on I-90 in the Columbia Basin.
The Lake Washington system supports important tribal and recreational salmon fisheries, though sockeye, which reside in the lake a year before going to sea, have not produced directed seasons for over 10 years, despite a new hatchery. WDFW’s Issaquah Salmon Hatchery produces Chinook and coho.
So far, the Muckleshoots have caught at least one northern pike in Lake Washington, as well as a handful of walleye in Lake Sammamish.
The LOAF also describes a plan to electrofish in spring and fall and gillnet in spring in select areas of Lake Washington and the Ship Canal, the idea being to figure out if removing bass, walleye, perch and other salmon predators can be effective.
One thing’s for sure, if you’re a bass tournament angler fishing nationally ranked Lake Washington, you’d want a map of where those efforts are planned.