Utilizing areas with high velocity tidal currents for energy production is a growing research field. However, empirical data concerning the effects of energy harvesting devices on marine organisms, e.g., fishes and their populations are largely unavailable. It is imperative that an empirical understanding of these interactions is established to better inform industry and consenting decision-makers. It is well known that fishes use tidal currents to move in tidal regions for foraging and reproductive purposes. However, specific information regarding fish use of the water column during high flows is lacking. Such information is vital to understanding fish interactions with hydrokinetic devices. We established down-looking hydroacoustic sampling protocols to determine seasonal patterns of fish vertical distribution before and after the installation of a hydrokinetic device in Cobscook Bay, USA. The proportion of fish tended to increase toward the seafloor, with some exceptions in spring. We were able to make comparisons to a nearby control site during times when a device was present. We found that vertical distribution before and after device installation only differed at the turbine site, perhaps as a result of fish re-distribution in response to the device.