The effect of boat sound on freshwater fish behavior in public (motorized) and wilderness (nonmotorized) lakes

Freshwater lake soundscapes yield crucial information regarding biological, geological, and anthropogenic activity, yet is a relatively unexplored area of study. These soundscapes are particularly important to aquatic life that may use sound to navigate, find food, avoid predators, and communicate. Further research is required to understand how aquatic species, such as native fishes, are impacted by increased anthropogenic interference. Many wilderness lakes restrict the use of motorized boats and equipment, providing an opportunity to compare fish behavior in the presence and absence of anthropogenic sound. Underwater videos and passive acoustic monitoring were used to evaluate fish behavior under different soundscapes in the upper Midwest United States: John Lake (nonmotorized, Boundary Waters Canoe Area Wilderness, MN), Rush Lake (nonmotorized, Huron Mountain Club, MI), and Caribou Lake (motorized, Duluth, MN). Intermittent short and long anthropogenic sound playback experiments showed behavioral changes in bluegill sunfish ( Lepomis macrochirus , centrarchids), bluntnose minnows ( Pimephales notatus , cyprinids), mimic shiners ( Notropis volucellus , cyprinids), and yellow perch ( Perca flavescens , percids). Overall, cyprinids in wilderness lakes were the most responsive to boat sound 36–52 dB above ambient sound levels, with bluegills in the public lake more likely to remain in the area during longer duration sound stimuli. Taken together, these results indicate that behavioral responses are species specific and depend on environmental variables such as anthropogenic exposure and fishing pressure.