Montana Fish, Wildlife, Parks has released the annual report detailing results from the lake trout removal project on Swan Lake. A three-year experimental lake trout removal project was initiated in 2009. The report describes the results of 2010.
A total of 10,021 lake trout ranging in size from 6-inches to 32-inches were removed by gill nets from Aug. 23 to Sept. 10, 2010. That time period was chosen because most adult bull trout are on their spawning run in the Swan River system and are absent from the lake. Bull trout by-catch was 299 fish and 40 percent of the netted bull trout died from the stress of capture. The remainder were released.
All lake trout less than 22 inches in length were cleaned, packed on ice, and sent to local area food banks for distribution. Fish greater than 22 inches were not retained for food bank distribution because of human consumption guidelines related to mercury content. Those fish were either given to local wildlife rehabilitation centers or were returned as biomass to the bottom of the lake.
During spawning area netting later in the fall, a total of 405 lake trout were caught and removed. Spawning lake trout ranged in size from 22 to 36 inches. Bull trout bycatch was 87 fish (about 40 percent died from the stress of capture).
Non-native lake trout were first detected in the Swan River system in 1998, and caused concern because of potential impacts to the threatened bull trout population as well as the popular kokanee salmon fishery. Research efforts to learn more about the lake trout population size and potential ways to reduce their numbers have been ongoing since 2006. Results of the three-year removal project will assist fisheries managers with future management of the lake trout population in Swan Lake.