A three-year-old fish production experiment in a northeast Washington lake is being evaluated to determine if an egg incubation method should be continued there.
Washington Department of Fish and Wildlife (WDFW) and Stevens County Conservation District staff this week will catch trout at Graham Lake to determine the relative survival of fish stocked in three different methods.
Graham Lake, a private water east of Colville chosen for the experiment because of its controlled access, was stocked with cutthroat trout as hatchery yearling, hatchery fry and in-lake incubated and hatched eggs. Each of the three groups was heat-treated in the egg stage to create distinct markings on the otolith (ear bone) of the fish.
In the analysis, WDFW staff will remove the otoliths from the caught fish and examine them in the department's Olympia laboratory for the markings, which resemble scanable bar codes used on retail products.
The results should show the relative survival rates of fish from each of the three stocking strategies, said WDFW district fish biologist Curt Vail.
Vail explained that in-lake egg incubation with remote-site incubators (RSIs), has worked well in large-scale operations in western Washington for chum salmon eggs. The sampling effort will determine if the method is also effective on a smaller scale on Graham Lake with cutthroat trout eggs incubated in five-gallon buckets.
"We'll see what the breakdown is when we get the lab work back," Vail said, "and then determine if it's cost-efficient to continue the RSIs."