Evaluation of a broadband sound projected from the gates of a navigation lock in the Mississippi River shows it to be a weak deterrent for common carp and unable to block passage

There is an urgent need to block the passage of carp and other invasive fishes through navigational locks in large rivers. Although the broadband sound of an outboard motor has been shown to strongly repel three species of carp in laboratory flumes and to a lesser extent inside of a lock chamber, it has not yet been tested to determineif it can stop carp from entering a lock. To test this possibility, we attached speakers to lock gates and played the sound of an outboard motor while measuring its efficacy by tracking free-ranging transplanted tagged common carp in its vicinity. Eight groups of 20 carp were tested while the sound system was turned on and off for 2 week periods. When the sound system was on, these carp spent approximately one-third less time in front of the lock gates than when it was off; however, when analyzed by a GLMM this effect was shown to be no greater than the effects of river discharge or temperature. Additionally, lock entrance rates were lower, albeit non-significantly, when the sound was off. A number of factors may have contributed to the limited efficacy of this deterrent system including the sound itself.