by Suzanne Vernon
For the Pathfinder
June 11, 1998
Anglers are finding fewer fish at Van Lake north of Condon this spring. According to Kalispell biologist, Scott Rumsey with Fish, Wildlife and Parks, the lake suffered a partial winterkill between fall of 1997 and spring of 1998.
"We're in the throes of having a few less fish out there," Rumsey explained. "It just won't be what people are used to."
Biologists surveyed the lake after the ice went out in response to reports of dead fish. Although eagles had quickly cleaned up the stressed and dying fish, Rumsey said biologists found some live fish remaining in the lake.
"It wasn't a complete winterkill, just partial," Rumsey explained. Fisheries managers speculate that the cause of the winterkill was oxygen deficiency.
"It's happened before on occasion there," Rumsey said. "But we were surprised it happened this year." He explained that the length of time that ice covers the lake, the thickness of the ice and the rate at which plants break down and use oxygen all contribute to a lack of photosynthesis, and oxygen depletion, which kills fish.
Van Lake is stocked with trout on a regular basis. The lake has no inlet or outlet, and no natural trout reproduction. Stocking will continue on a regular basis, Rumsey explained.
Elsewhere in the Swan Valley, Rumsey said biologists will be surveying high mountain lakes, Holland Lake and Lindbergh Lake this summer. Earlier this spring, they conducted gill net studies at Swan Lake and found fish population trends to be consistent with past surveys.
Swan Lake is the only lake in the state where anglers can legally fish for bull trout.
"Bull trout numbers are good there," he explained.
Anglers have complained of a lack of kokanee at Swan Lake this spring. Rumsey speculates that the kokanee are more dispersed in the lake this spring due to fluctuating water temperatures, and that anglers will find more fish when water temperatures "layer out" he said.
Rumsey reminded anglers that it is illegal to fish for bull trout anywhere else in Montana, including the Swan River and its tributaries.