Swan Valley Bull Trout Working Group

The Swan Valley has historically been home to a stable, healthy bull trout population. In recent times Bigfork Dam had been considered an important asset in isolating the Swan watershed from the threat of non-native lake trout invasion, which has decimated other lake-dwelling bull trout populations in northwest Montana. However, in 1998, anglers began catching and reporting adult sized (20-30 inch) lake trout from Swan Lake and the Swan River. In 2003, the level of concern was compounded when MFWP gill netted a 9-inch juvenile lake trout from Swan Lake. This provided the first evidence of lake trout reproduction in the system. A similar survey in 2004 captured 7 more juvenile lake trout. In 2005, the number of lake trout captured continued to grow. These data led biologists to conclude that lake trout presence is a growing threat to the bull trout populations of Swan Lake, Lindbergh Lake, and Holland Lake.

These findings served as a catalyst in the formation of a Swan Valley Bull Trout Working Group. The SVBTWG is composed of five government agencies and Trout Unlimited. We determined that, if left unchecked, it is only a matter of time until lake trout will become the dominant piscivore in the Swan River ecosystem. The SVBTWG was formed in 2004, formalized in 2005, and in the past year the group has made their first substantial progress in addressing the lake trout threat.

This page will serve as a repository for information regarding the SVBTWG and the situation in the Swan Valley watershed. If you have material that you would like added please send to michaelg@montanatu.org .