Montana Fish, Wildlife & Parks and the Swan Valley Bull Trout Working Group have recently completed an annual report detailing the lake trout removal project in Swan Lake and the status of bull trout and kokanee in the Swan valley. 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 experimental removal project will assist fisheries managers with future management of the lake trout population in Swan Lake.
This was the fourth year of targeted gillnetting to remove non-native lake trout in Swan Lake. A total of 10,413 lake trout ranging in size from 5-inches to 32-inches were removed by gill nets during the juvenile netting portion of the project which was conducted from August 12 to August 31, 2012. This 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. Netting conducted along the lake trout spawning area later in the fall (October 8-25) resulted in an additional 215 adult lake trout being caught and removed. Spawning lake trout ranged in size from 20 to 36 inches. Bull trout bycatch was 432 fish for the entire 2012 netting effort, with approximately 60% of those fish being released alive.
Maintaining robust populations of bull trout and kokanee remains a priority for this project and those key species are monitored annually. After four years of declining both bull trout and kokanee redd counts, the 2012 surveys revealed a slight increase in both species. While the 2012 redd counts still remain lower than average, the slight increase should be viewed as positive and the trend will be closely followed in upcoming years to determine if netting is being effective.
For more information, please see the attached Swan Lake Trout Removal Project 2012 Annual Report.
Contact: Leo Rosenthal, Fisheries Biologist, 751-4548