Biologists fish for answers about the trout in Hidden Lake

Ice vanished last week from the gorgeous, glacially carved 4 1/2-mile long Hidden Lake on the Kenai Peninsula.

That means one of the largest populations of lake trout on the Kenai Peninsula will be cruising the shallow waters of the 1,596-acre lake the next couple of weeks.

"We fish from ice out to the middle of June," said Matt Moore of Soldotna, who has fished it for years. "It took me a lot of trial and error and talking to old-timers around here to get a handle on Hidden Lake. It's a pretty pristine fishery, and more and more people are figuring it out."

Hidden Lake's pink-flesh lake trout average 2 to 4 pounds. The winner of the Soldotna Trustworthy Ice Fishing Derby in February was Douglas Lee's 7-pound lake trout from Hidden Lake, and a year ago Larry Wall's 12 1/2-pounder topped the field.

Alaska's largest freshwater fish can grow big. The state record, caught on Clarence Lake in 1970, weighed 47 pounds. Moore has had a Hidden Lake fish on his line he estimated at 20 pounds, and he said he landed a 15-pounder through the ice last year shortly after the derby ended.

Ken Gates of the U.S. Fish and Wildlife Service in Kenai is trying to get his arms around the size and status of the lake trout in Hidden Lake. Two months ago, working with cooperative ice fishermen, his office tagged and released 22 of them, an effort expected to resume later this month.

"Within the past few years, anglers and management biologists have become concerned about the health of the lake trout population in Hidden Lake," he said, pointing to declines in angler-reported harvest over the past decade.

Sharp declines in the legal bag limit from 12 lake trout a day to just one fish might lead to the perception among anglers that fishing has declined.

"I fish it a lot, and I think it's gone downhill the last 5-10 years," Wall said. "I can't figure out what's going on. Used to be you could go out there and catch 10 of them, but now maybe it's just one or two and they're small."

He's not alone in his views.

"I really don't have any sense for it, and I don't think anybody has any real data about what is going on," Gates said.

Biologists consider lake trout susceptible to overharvesting because they grow slowly and don't spawn before they're 5 years old -- and then only every other year. They are actually char, not trout, and can live up to 50 years.

"I caught a 30-pounder out of there in March of 1985," Wall said. "I had to squeeze him through the hole in the ice."

Biologists like Gates hope to learn how many mature fish are in the lake and what kind of fishing pressure the population can withstand.

First he hopes to identify where lake trout spawn in September and October as well as the distribution and movement of mature fish at least 18 inches long by tagging the fish with radio transmitters and then tracking them by boat until ice up.

Transmitters are surgically implanted in the stomach cavity of lake trout after biologists make a one-inch incision on the ventral side and slide in the transmitter.

"They do rather well with it, believe it or not," Gates said.

With detailed fish weight and length data, Gates hopes to be able to zero in on the population's harvest potential.

"Lake trout are typically managed conservatively," he said.

Hidden Lake extends some eight miles into the foothills north of Skilak Lake.

Each June, red salmon smolt gather in the lake by the hundreds of thousands before migrating down Hidden Creek to Skilak Lake. Up to 30,000 adults return to spawn in June and July.

Brown and black bears patrol the dense growth along the creek south of the lake. Songs and calls of hermit and Swainson's thrushes, boreal chickadees, warblers and red-breasted nuthatches can fill the air.