Sound production of spawning lake sturgeon (Acipenser fulvescens Rafinesque, 1817) in the Lake Winnebago watershed, Wisconsin, USA

The primary goal of this study was to obtain accurate data of previously undocumented lake sturgeon (Acipenser fulvescens Rafinesque, 1817) spawning sounds, generated during wild sturgeon reproduction. Biologists have long known that lake sturgeon produce low-frequency sounds during spawning bouts; energy from these sounds can break the surface of the water occasionally and propagate harmonics in the terrestrial atmosphere, creating a faint drumming popularly known as ‘sturgeon thunder’. Understanding the contribution of this sonic behavior in context is essential for gaining a more comprehensive scientific appreciation of the process of sturgeon spawning, and accurate acoustic data should prove useful for fisheries managers seeking to monitor or enhance sturgeon stocks for reproductive activity. Recordings were made at several locations on the Wolf and Embarrass rivers during the 2011–2013 spawning seasons. Drumming sounds ranging from 5 to 8 Hz fundamental frequency were evident. Other characteristic noises associated with spawning lake sturgeon, including low-frequency rumbles and hydrodynamic sounds, were identified. Other high frequency sounds were also discovered. All of these sounds coalesce into a distinctive acoustic signature of lake sturgeon spawning activity. Knowledge of this sonic signature can be used to accurately document reproductive activity at multiple locations over extended periods using remote recording tools and techniques.