The effect of sound produced by vessel passage at a navigational lock on freshwater fishes

The effects of anthropogenic sound on freshwater animals has received considerably less attention than their marine counterparts. Physical barriers such as dams in rivers and lakes, provide flood protection and generate hydroelectric power, but can also hinder fish movements. Fish that transit navigational locks adjacent to dams are exposed to vessel and machinery sound which could have deleterious effects to auditory sensitivity. To understand the effect of lock sound on fishes, passive acoustic monitoring was conducted at Lock and Dam 5 near Winona, Minnesota, USA during ice-free months (November 2017, April - September 2018) to coincide with peak vessel activity. Commercial vessel (tow boats with up to 12 barges) transits increased sound levels by up to 40 dB [median broadband SPL (200 - 1, 000 Hz)], inside the lock chamber while recreational boat transits increased sound by up to 35 dB. All fish species studied to date detect sound (either pressure or particle motion) in their environment, indicating that it is an important cue. Comparing the passive acoustic dataset to known auditory thresholds for native and invasive fishes of the Mississippi River, it is suggested that fishes that become trapped in the concrete lock chamber may undergo shifts in auditory sensitivity.