Effectiveness of a 17-Year Removal Program for Non-Native Lake Trout in Yellowstone Lake, Yellowstone National Park

Introduced lake trout (Salvelinus namaycush) threaten to extirpate native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) in the 34,000 ha Yellowstone Lake in Yellowstone National Park.  Suppression (and eventual eradication) of the lake trout population is deemed necessary for the conservation of Yellowstone cutthroat trout.  A National Park Service gill-netting program removed about 830,000 lake trout from Yellowstone Lake from 1995 through 2011.  We used statistical catch at age and matrix population models to assess the efficacy of the lake trout suppression program.  The current rate of population growth is positive; however, it is lower than it would be in the absence of lake trout suppression.  Fishing effort needs to increase above observed levels to reduce population growth rate below replacement.  Additionally, high sensitivity of population growth rate to reproductive vital rates indicates that increasing fishing mortality for sexually mature lake trout may increase the effectiveness of suppression.  Lake trout suppression in Yellowstone Lake illustrates the complexities of trying to remove an apex predator to restore a relatively large remote lentic ecosystem with a simple fish assemblage.