Loon Lake kokanee crash a mystery

Bill Baker has a mystery on his hands.

The supply of kokanee salmon in Loon Lake has crashed in recent years, turning the popular fishery north of Spokane into a bit of a disappointment.

Instead of finding large numbers of landlocked salmon in the 10- to 12-inch range, anglers are finding small numbers of really big fish – a sign that some entire age classes of kokes have disappeared.

And Baker, the Washington Department of Fish and Wildlife fisheries biologist who manages the lake, has no clear answer for the obvious question: Why?

“It’s a headscratcher,” Baker said.

Anglers have long seen Loon Lake as a top destination for night fishing for kokanee. It has been considered a consistent producer of good numbers of fish, aided in part by annual fry plantings of 85,000 to 100,000 fish from 2005 to 2022.

Something seemed to happen around 2020 or 2021, however. Baker said they started to see fewer kokanee caught, and the ones that were caught were bigger than usual.

In 2023 and 2024, anglers were mostly catching large kokanee, including some up to 20 inches.

That’s a fine trophy, but also a sign of trouble. Kokanee are density dependent, meaning that they grow big when there are fewer of them around. Catching big kokanee means there are just fewer of them around.

“It’s super frustrating,” Baker said. “We kind of went from a lot of years of really consistent survival of those fry plants and whatever was being produced naturally in the lake to all of a sudden the population just crashing. We don’t know at this point what’s causing it.”

This year, they’re trying to put a Band-Aid on the problem. By begging and borrowing from other parts of the state, WDFW rustled up 300,000 kokanee fry to put in the lake – about triple the amount that’s normally stocked.

Stocking began in mid-May and carried on into June. Baker said they hope boosting the number of fry stocked will in turn boost the number of adult fish that show up in angler catch data. In the fall, WDFW plans to sample the lake and see if the fish have survived the summer.

If they have survived, it will help Baker begin to rule out some potential causes of the decline and begin to form some sort of hypothesis.

He’s thought through some of potential obvious answers. Loon Lake is full of zooplankton, which kokanee love to eat, so Baker doesn’t think food availability is the problem.

A predator problem also seems unlikely. There are bass, tiger trout and lake trout in the lake, both of which eat young kokanee. But Baker said declines caused by predators tend to happen slowly, with numbers creeping downward over time.

In this case, the drop happened almost overnight.

“It was an all of a sudden thing where these year classes of kokanee were just not surviving,” Baker said.

WDFW did modestly increase its stocking of kokanee fry in 2023 and 2024, but that didn’t turn the tide.

Putting in 300,000 fry is a bit of a Hail Mary – if that doesn’t work, it’s hard to see what would. Baker is hoping those fish will at least survive the summer.

“Any fish that we can sample in the fall and tell that they’re still present is going to be a positive sign,” Baker said.