Cooperative Fish and Wildlife Research Units Program: Idaho
Education, Research and Technical Assistance for Managing Our Natural Resources

Knowledge of the population structure and dynamics of nonnative species is critical for determining potential problems and solutions for management. Numerous species have been introduced to Coeur d’Alene Lake, Idaho over the last century, but minimal research has been completed to understand their population dynamics. The objective of this study was to describe the population demographics and dynamics of northern pike Esox lucius and smallmouth bass Micropterus dolomieu, two important nonnative sport fishes in the system. Age and size structure of northern pike and smallmouth bass were similar across bays. The oldest northern pike was age 7 and the oldest smallmouth bass was age 11. The recruitment coefficient of determination was 0.99 for northern pike and 0.98 for smallmouth bass, indicating very stable recruitment. Total annual mortality was estimated as 66% for northern pike and 42% for smallmouth bass. Growth of northern pike in Coeur d’Alene Lake was comparable to the 50-75th percentiles of growth exhibited by lentic northern pike populations across North America. Growth of northern pike in Coeur d’Alene Lake was most similar to populations in the north-central and northeast United States with fast growth rates and short life spans. In contrast, smallmouth bass growth was extremely slow and generally fell within the 5th percentile of lentic smallmouth bass populations in North America. Smallmouth bass growth in Coeur d’Alene Lake was similar to other populations in northern regions of the United States displaying slow growth rates with high longevity. Results of this study provide important insight on nonnative northern pike and smallmouth bass population dynamics.