More on the frequency dependence of target strength of mature herring
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The hibernating stock of Norwegian spring-spawning herring has been acoustically surveyed in a fjord system in northern Norway in December 1992. The survey frequencies are 18, 38, 120, and 200 kHz. When the corresponding echo sounders were operating, the fundmental measurements of volume backscattering strength were simultaneous. By comparing integrated measures of these, the several backscattering cross sections are related. New results are compared with those obtained from a cruise in the same area in December 1991, when the same herring stock was observed.