Measurements of the target strength of fish

Measurements have been made at 30 kc/s of the target strength of dead cod, herring, plaice and perch. Four independent series of measurements have been made between 1955 and 1959.In three of the series, false Onazote swimbladders were placed in the body of the fish to simulate the acoustic properties of the normal swimbladder. The results are tabulated and presented in a graph, the reference level being the target strength of a sphere of 2 m radius. The results are discussed in relation to the frequencies which are most likely to be suitable for echo-sounding on fish targets when quantitative data are required.