A three-year study on Swan Lake shows gill-netting efforts effectively reduced young lake trout.
Montana Fish, Wildlife and Parks officials and members of the Swan Valley Bull Trout Working Group recently completed a report on the three-year experimental lake trout removal project for Swan Lake.
In the coming month, an environmental assessment for an extension of this research will be released for public comment. When finalized, this project will guide the future management of Swan Lake.
From 2009-2011, a total of 21,330 lake trout, measuring between six to 36 inches long, were removed from the lake. The catch rate increased between 2009 and 2010, then decreased in 2011, leading officials to believe netting efforts were effectively reducing recruitment of young lake trout into the population. Catching predominantly newly recruited lake trout in 2010 and 2011 supported that notion, FWP said.
By-catch of non-targeted fish species, like bull trout incidentally being caught, was relatively low throughout the project, FWP said. However, officials said inadvertent catches and associated bull trout mortalities remain a concern. FWP said efforts were made to minimize by-catch mortality, including properly and placing netting and reviving captured fish. This concern is compounded by an observed decreasing trend of adult bull trout abundance, reflected by redd counts, in recent years in the Swan drainage, FWP said.
Officials believe the declining bull trout trend may be caused by a combination of several factors including gill-netting by-catch, lake trout competition and/or predation, and angler harvest. This trend will be closely monitored in upcoming years, FWP said.
To view the final report on the three-year project, visit FWP’s website.