Population Dynamics and Evaluation of Alternative Management Strategies for Nonnative Lake Trout in Priest Lake, Idaho

Abstract

Lake Trout Salvelinus namaycush have been introduced widely throughout the western USA to enhance recreational fisheries, but high predatory demand can create challenges for management of yield and trophy fisheries alike. Lake Trout were introduced to Priest Lake, Idaho, during the 1920s, but few fishery-independent data are available to guide current or future management actions. We collected fishery-independent data to describe population dynamics and evaluate potential management scenarios using an age-structured population model. Lake Trout in Priest Lake were characterized by fast growth at young ages, which resulted in young age at maturity. However, adult growth rates and body condition were lower than for other Lake Trout populations. High rates of skipped spawning (>50%) were also observed. Model projections indicated that the population was growing (λ = 1.03). Eradication could be achieved by increasing annual mortality to 0.32, approximately twice the current rate. A protected slot length limit could increase population length-structure, but few fish grew fast enough to exit the slot. In contrast, a juvenile removal scenario targeting age-2 to age-5 Lake Trout maintained short-term harvest of trophy-length individuals while reducing overall population abundance.

ACKNOWLEDGMENTS

We thank C. Brown, K. Griffin, J. Johnson, N. Porter, T. Schill, M. Terrazas, and S. Whitlock for their assistance with field research, and Hickey Brothers Fisheries for assistance with netting. We also thank T. Johnson, Z. Klein, J. Rachlow, D. Schill, J. Syslo, and three anonymous reviewers for their helpful comments on an earlier version of the manuscript. Funding for this project was provided by the Idaho Department of Fish and Game through the Federal Aid in Sport Fish Restoration Act and by Idaho anglers via license fees, along with the Kalispel Tribe of Indians. Additional support was provided by the U.S. Geological Survey, Idaho Cooperative Fish and Wildlife Research Unit. The Unit is jointly sponsored by the University of Idaho, U.S. Geological Survey, Idaho Department of Fish and Game, and Wildlife Management Institute. This project was conducted under the University of Idaho Institutional Animal Care and Use Committee Protocol 2012-22. The use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government.