An Outboard Boat Motor Sound Deters Carps in a Lock Chamber As Well As in a Laboratory Tank

There is an urgent need to develop species-specific deterrent systems for bighead and silver carp (Hypophthalmichthys spp.) which are moving up the Mississippi River and its tributaries.  Sound stimuli have special promise for carps because these species have an exceptional sense of hearing compared to most fishes native to the Mississippi River Basin.  We explored the theory and application of using sound to control bigheaded and common carp (Cyprinus carpio) movement in both laboratory and field settings.  In the laboratory, we tested an unmodified (10-10,000 Hz) and a frequency-filtered (>1000 Hz) outboard boat motor sound.  Silver, bighead, and common carp all avoided the unmodified boat motor sound but not the filtered sound.  However, carp habituated to the unmodified sound following repeated (3-4) exposures.   Lake sturgeon (Acipenser fulvescens) did not avoid either signal. Tests with common carp and lake sturgeon in the auxiliary lock chamber at Lock and Dam #1 (St. Paul, MN), were consistent with laboratory observations with carp avoiding the sound and minimal impacts observed for sturgeon.  Our results suggest that specific acoustic stimuli could be used to deter the movement of invasive carp with minimal impacts to many native species.  (Funded by the MN ENRTF).