Long-term suppression of the Lake Trout ( Salvelinus namaycush ) population in Lake Pend Oreille, Idaho

A simulation model of lake trout Salvelinus namaycush (Walbaum 1792) population dynamics in Lake Pend Oreille, Idaho, was used to estimate (1) the optimal allocation of effort among gillnet mesh sizes that minimizes abundance in the shortest time; (2) the number of years needed to suppress the population to 90% of peak abundance; and (3) once suppressed, how much effort could be reduced to sustain abundance indefinitely. A density-dependent stochastic simulation model was parameterized from data in 2006–2016, including parameter uncertainty and implementation error. Time to suppression could be reduced by using more large-mesh gillnet than was used during 2007–2016. Continued fishing at the peak level of total gillnetting effort, but using an optimal effort allocation among meshes, would suppress abundance to the target level within 7–13 years. Once suppressed, gillnet effort could be reduced 76–86% (157,000 m, 95% CI 116,000–199,000 m) to sustain abundance at the target level. Our findings suggest that time to suppression of lake trout populations in other systems may be able to be reduced by optimizing gillnet effort allocation among mesh sizes, and that total effort can be greatly reduced to sustain abundance at the reduced level thereafter.