History
An extremely wide variety of fish taxa produce sound. Sound production behavior provides an opportunity to study various aspects of fish biology, such as spawning behavior and habitat selection, in a noninvasive manner. Passive acoustic methods can be an attractive alternative or supplement to traditional fisheries assessment techniques because they are noninvasive, can be conducted at low cost, and can cover a large study area at high spatial and temporal resolution.
Following the First World War, when sonar was first used for the detection of submarines, echo sounders began to find uses outside the military. The French explorer Rallier du Baty reported unexpected midwater echoes, which he attributed to fish schools, in 1927. In 1929, the Japanese scientist Kimura reported disruptions in a continuous acoustic beam by sea bream swimming in an aquaculture pond.
In the early 1930s, two commercial fishermen, Ronald Balls, an Englishman, and Reinert Bokn, a Norwegian, began independently experimenting with echosounders as a means to locate fish. Acoustic traces of sprat schools recorded by Bokn in Frafjord, Norway was the first echogram of fish to be published. In 1935, Norwegian scientist Oscar Sund reported observations of cod schools from the research vessel Johann Hjort, marking the first use of echosounding for fisheries research.
Sonar technologies developed rapidly during the Second World War, and military surplus equipment was adopted by commercial fishers and scientists soon after the end of hostilities. This period saw the first development of instruments designed specifically to detect fish. Large uncertainties persisted in the interpretation of acoustic surveys, however: calibration of instruments was irregular and imprecise, and the sound-scattering properties of fish and other organisms was poorly understood. Beginning in the 1970s and 80s, a series of practical and theoretical investigations began to overcome these limitations. Technological advances such as split-beam echosounders, digital signal processing, and electronic displays also appeared in this period.
At present, acoustic surveys are used in the assessment and management of many fisheries worldwide. Calibrated, split-beam echosounders are the standard equipment. Several acoustic frequencies are often used simultaneously, allowing some discrimination of different types of animals. Technological development continues, including research into multibeam, broadband, and parametric sonars.
Read more about this topic: Fisheries Acoustics
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