Hydrografiske undersøkelser og kartlegging av plankton og fiskefordeling i Nordsjøen og Norskehavet i juni - juli 1972

Abstract

In June—July 1972 R. V. «G. O. Sars» carried out a survey in the northern North Sea, Skagerrak and the adjacent waters of the Norwegian Sea. The general features of the hydrography was determined, the relative abundance of fish estimated by means of echo integrator readings and the fish species identified by bottom trawl and mid water trawl samples. The disribution and relative abundance of plankton, fish eggs and larvae was investigated in the northern North Sea and Skagerrak. The North Sea and Skagerrak area may be divided into three subareas reflecting significant differences in the hydrographic conditions, viz. the Norwegian Deeps (A), the Danish coast (B) and the northern North Sea plateau (C). Plankton concentrations were highest in two separated eddies of surface water located to the west of the Norwegian Deeps and characterized by relatively low temperatures. The distribution of the dominating fish species was found to be fairly closely related to particular water masses. Blue whiting and also greater silver smelt were abundent in the deeper parts of the Norwegian Deeps. Dense concentrations of adult Norway pout as well as the 0-group were found in the slow moving cooled water masses in the central part of the northern North Sea. In the Norwegian Sea the distribution of blue whiting was restricted to the thermocline between O'^ and 2^C. The densest concentrations were observed along the continental slope from the Faroes towards eastern Iceland.