Influence of Three Sonic Devices on Fish Behaviour

Three sound emitting devices have been developed to control fish movement in the vicinity of generating stations. These devices have the advantage of increased flexibility in terms of frequency and amplitude over most previous sound devices and show potential for repelling and/or attracting some species of fish. One device, the 'fishdrone', uses sonic vibrations to excite a metallic structure at selected resonance which is then transmitted into the water column. This unique characteristic allows the fishdrone to be turned in response to the target species for either attraction or repulsion purposes. The second device involves a speaker assembly which plays back the sounds of predators and has been used by the Japanese to deter anchovies in Manimota Bay. This system is capable of generating natural sounds of predators or fish in distress in a randomized fashion.