Cost-Effectiveness of Gill Netting Strategies for Suppressing Non-Native Lake Trout in Swan Lake, Montana

Mechanical removal of non-native lake trout has become a common management endeavor for large lakes in the Intermountain West.  Eradication is not a likely outcome given current technology; therefore, management goals may best be quantified as the greatest reduction in lake trout abundance possible for a given time frame and cost.  We developed a population model to assess the efficacy of 41 management scenarios.  Each scenario was a temporal combination of netting actions, where one of four actions could occur in a given year (i.e., no netting, targeting subadults, targeting spawning adults, or targeting subadults and spawning adults).  Reductions in abundance generally increased as a function of annual cost; however, substantial variation existed in the reduction that can be achieved for a given cost.  For example, the most expensive scenario (harvesting subadults and spawning adults every year) resulted in the greatest decline in abundance after 10 years (reduction of 0.986; 0.968-0.995 95% CI). However, other scenarios (e.g., alternating harvest of both subadults and spawning adults with harvest of spawning adults only) produced similar results with a 35% reduction in cost.