Fishing for answers

By AMY MAY- The Daily Inter Lake

Swan Lake has long been considered a safe haven for bull trout from the invasion of non-native intruders. But according to wildlife officials, in the last 10 years the fight has evened as the invading lake trout population has exploded.

Before the bull trout population in Swan Lake is truly threatened, biologists are taking an active approach to protect the fragile species.

Wildlife experts from seven different agencies on Monday began an extensive study of the trout populations in Swan Lake.

The three-week survey of lake trout is expected to give biologists an idea of their behavioral and spawning patterns.

Wade Fredenberg of the U.S. Fish and Wildlife Service is one of the key coordinators of the study.

"The Swan has always had such a strong and vibrant bull trout population that many thought couldn't be threatened. This is one of the most important turning points in my 30-year career," Fredenberg said of the current sampling program.

According to Fredenberg, this study is different because the information collected may help preserve the bull trout population while it is still strong.

"This effort is unique, because the bull trout population in Swan Lake is in good shape," Fredenberg said. "The system is small enough that we can get in the game early and hopefully make a difference."

Reports of lake trout began coming in from area fisherman in 1998. By 2003 the second generation of lake trout began to appear in Swan Lake, meaning the species had successfully invaded the lake system.

The competitive and predatory interactions between bull and lake trout are still a mystery, even for experts.

Fredenberg said that both species are similar enough to live in the same niche, but spawning patterns and life spans give lake trout a competitive advantage.

"All across the Northwest and Canada there is a strong track record showing that introduced lake trout consistently out-compete bull trout," he said.

With the hopes of keeping the Swan Lake lake trout population in check, the study participants will use radio transmitters and computer chips to identify spawning sites.

Twice a day for the next month a crew out of Wisconsin and a number of wildlife biologists will set up nets to collect fish. Two types of nets are being used in the process.

Deep-water trap nets are large "living room-sized" net boxes that rest on the bottom of the lake in water deeper than 60 feet. Fish trapped in this manner usually swim passively around the box and can be retrieved unharmed when the box is lifted to the surface.

Gill nets also are being used. They work like submerged fences. Fish swim along the fence until they try to cross through, then the fish get caught. With 15 nets strung together, the gill nets reach nearly a mile in length.

On Tuesday, the second day of sampling, Fredenberg and Scott Hawxhurst of Montana Fish, Wildlife and Parks both marveled at the capacity and ability of the commercial fishing boat being used for the study.

"We'd never be able to do anything this with our own boats," Fredenberg said as he watched the crew feed a mile of gill net out the stern of the black-and-yellow R/V Finn.

The $40,000 study is funded mainly by the U.S. Fish and Wildlife Service with help from the U.S. Forest Service and Trout Unlimited.

Data from the study will be analyzed over the winter and by next spring a plan of action should be determined. The long-term goal of the study is to decide whether or not lake-trout suppression in Swan Lake is necessary to ensure the continued survival of bull trout.

"Native bull trout are a big part of the legacy that we inherited from our predecessors in this valley," Fredenberg said. "It's crucial that they not disappear on our watch."

Reporter Amy May can be reached at 758-4459 or by e-mail at amay@dailyinterlake.com