Acoustic Deterrents

Along with dyed bait, acoustic deterrents are by-catch reduction devices (BRDs).

Defenition of Acoustic Deterrents - An acoustic system and a method for repelling marine mammals from a region of water. Acoustic deterrents use groups of acoustic transducers, which are placed beneath the surface of the water, to emit high frequency acoustic signals (in sequence order). The power of the acoustic signals starts at a low level and rises until it eventually reaches a level that produces a signal that is beyond the threshold of pain for the mammels that are trying to be repelled from that specific region of water. By using acoustic deterrents, marine animals are repelled from an area without suffering permanent hearing loss.
An acoustic deterrent
An acoustic deterrent

Acoustic deterrents (also called pingers) are a very effective way of keeping cetaceans and other marine animals from becoming victims of by-catch. While acoustic deterrents are very effective, they do have some negative effects on the environment and marine mammals. Habitat exclusion, habituation, and hearing damage are a few of many side effects of using acoustic deterrents. Although there are negative effects of using acoustic deterrents, they are extremely helpful in keeping many marine animals safe.

For more information on acoustic deterrents, visit http://www.leidenuniv.nl/cml/ssp/students/richard_franse/acoustic_deterrent_uk.pdf, or http://www.freepatentsonline.com/5610876.html