Investigations on hydrography and fish distribution in the North Sea in February 1972

The present report outlines the results of a survey carried out by R. V. "G. O. Sars" and R. V. "Johan Hjort" in February 1972. The distribution and relative abundance of fish in the North Sea were mapped on the basis of echo integrator readings. Samples obtained by mid water and bottom trawls supported the identification of echo recordings and provided material for biological analyses of dominating fish species. The general features of the hydrography was determined, and the distribution of air and sea temperatures, temperature anomalies, and salinities are presented. Significant differences in echo integrator readings were observed: between day and night, between the two ships and in relation to obtained catch. Bottom trawl catches varied between 45 and 1545 kg per hour. Best catches were taken in the southeastern part of the North Sea. In total, herring, whiting and haddock amounted to 26, 25 and 21 per sent respectively while Norway pout, flatfish and other species each were less than 10 per cent in weight. Distribution, size, age etc. are reported in detail for the dominating species, and the relationship between the distribution and the abiotic environment is discussed, Young herring were found in greatest concentrations in the Bløden area. Sprat were found in the coastal waters, characterized by relatively low salinity, while Norway pout were most numerous in Atlantic water in the northern part on the North Sea plateau. Blue whiting and coalfish were mainly observed along the western slope of the Norwegian trench below the core of the Atlantic water which penetrates into the North Sea