Meeting Abstract
Invasive silver carp (Hypophthalmichthys molitrix) dominate large regions of the Mississippi River Drainage in North America, outcompete native species, and continue to expand northward, threatening the Laurentian Great Lakes. Silver carp have an unusual jumping strategy that is well documented in news and media outlets but the trigger for jumping remains unclear. Field trials on the Illinois River revealed that silver carp primarily jump behind and away from fast moving (16 – 32 km/hr) boats. The outboard motors (100 – 150 hp motor) emit broadband sound with energy peaks from 0.10 – 2 kHz and 6 – 10 kHz and captive silver carp demonstrated consistent negative phonotaxis (reacting up to 37 times consecutively) to an outboard motor recording. The same sound stimulus (170 dB re 1 μPa SPLrms) also elicited jumping behavior in wild fish when played from a slow moving boat (> 5 km/hr) in the Spoon River near Havana, Illinois. Silver carp are ostariophysans and possess Weberian ossicles that allow for high frequency hearing compared with non-ostariophysans. Auditory evoked potentials indicated that silver carp could detect up to 5 kHz with the lowest threshold at 500 Hz (80.6 ± 3.29 dB re 1 uPa SPLrms). This research implies that broadband sound between 500 Hz – 5 kHz can be used to alter the behavior of silver carp and has implications for deterrent barriers or other uses (e.g. herding fish) that are important to fisheries managers. Research was supported through the University of Minnesota Duluth, the Minnesota Environment and Natural Resources Trust Fund, the U.S. Geological Survey, and the Illinois Natural History Survey.
