Echo abundance indices of 0-group fish in the Barents Sea, 1965-1972
Journal article, Peer reviewed
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In order to obtain estimates of year class strength of 0-group fish, joint international surveys have been conducted each year since 1965 in the Barents Sea. The density of fish has been estimated by visual grading of the echo-sounder paper recordings and the scattering layers have been identified by small meshed pelagic trawls. The year class strengths of the species under consideration have been stated to be poor, average or strong, and this grading has so far been based on the experience of the participating scientists. In the present paper, abundance indices for each year are calculated for the most important species. The indices are based on the visual density grading of the echograms and on the size of the trawl catches. Echo integrator readings are used to calculate the true ratio between the 'visual' density groups. The usefulness of such indices will increase with increasing knowledge of the sound reflecting properties of the scatterers.