To minimize mortality, Hydro-Québec’s power station located on the Des Prairies River (Montréal, Canada), used to stop its operation for one hour every day during the post spawning migration of American shad (Alosa sapidissima). The corresponding water volume was then spilled (via the spillway) to produce a preferential flow for the fish. It was shown that during this period, up to 95% of the shads located in front of the power station swam away from it, toward the spillway. However, during the remaining hours of operation there was a high probability that shad would go through the turbines to complete their journey back to the ocean. To reduce this potential mortality, Hydro-Québec has been experimenting since 2006, with an ultrasound barrier operating at a minimum noise level of 168 dB ref 1µPa at 125 kHz to prevent shads from approaching the power station. From our experimental and bibliographical data, these values have to be met to ensure the success of the American shad guidance. Consequently, since 2010 the power station did not have to stop its operation during the American shad downstream migration. A final prototype developed with Hydro-Quebec’s Research Institute is now in use. Plans are made to guide American shad to an alternative route where no power station is present.