Impingement of fish into hydroelectric dams and water intakes to power plants is a significant problem in many parts of the United States. The problems are two-fold. First, many fish are killed when they encounter the dams or intakes and cannot escape the rapidly flowing water. Second, there is potential damage to the power generating equipment due to the large number of impinged fish. Thus, it is of considerable economic importance to find ways to prevent the interactions between fish and the dams or power plant intakes. One of the most successful methods developed to date is the use of high frequency sound to repel clupeid fishes (herrings and relatives) from these obstacles. For reasons that are yet unknown, these commercially important species swim away from these sounds. At the same time, we know very little about how clupeids detect the ultrasonic sounds, or the kinds of sounds that can be most successfully used to repel the fish. The purpose of this study is to examine the hearing ability of clupeids in order to better understand how they detect sounds, and which sounds they detect, with the ultimate goal being to develop methods to more effectively prevent the impingement of clupeids at dams and power plant intakes.
