Some anglers were disturbed this month to read that fish biologists are using nets to survey fish populations at Lake Roosevelt.

The method is used across North America and has nothing to do with the state’s current proposal to liberalize catch limits of walleye and bass in the reservoir and some other waters, said Chris Donley, Washington Department of Fish and Wildlife inland fisheries manager.

Three survey methods are used in Roosevelt and other waters:

• Gillnets, which kill a small number of fish.

• Trap nets, from which fish can be released alive.

• Electroshocking, which temporarily stuns fish so they can be scooped with nets, inventoried and released.

“Each type of gear has a different bias, so we use all three to help get a better picture of the fisheries,” Donley said.

For example, gillnets are good at targeting walleyes, but are inefficient at sampling smallmouth bass. Trap nets are best for sampling forage fish. Electroshocking is good for shoreline-oriented fish and all sorts of juvenile fish, but misses fish in deeper water.

Understanding the numbers of forage fish is key to managing the sport fish, Donley said.

Surveys are conducted at different times of year and in various portions of the reservoir.

“Fish move throughout the year, and the reservoir is huge,” Donley said, noting that Roosevelt ranges to 150 miles long.

That’s also part of the reason anglers can have good luck one week and find no fish the next, he said.

“We know we’ve lost a lot of trout and kokanee (flushed through Grand Coulee Dam) in the last two big water years,” Donley said. Some walleye likely were washed out of Lake Roosevelt, too, but to a much lesser degree, he added.

“Our data tell us there’s still a lot of walleye in the lake.”