Bunnfisk på den norske kontinentalskråning

Abstract

Investigations of distribution and abundance of demersal fish in 400—1000 m depth were carried out in three selected areas off Norway in July—August 1974. Based on catches in 48 hauls by bottom trawl and 3 longline settings the relationships between depth, fish quantity and species composition were determined. In 800 m the catch in weight was reduced to about 10 percent and in 1 000 m to 1 percent of that taken on the edge of the shelf (400—500 m). The number of fish species caught was reduced from about 10 to 3 over the same depth range as boreal species were replaced by a few arctic species. Trawl catches were small, about 70 kg per hr in 600 m, while longline in this depht gave 150 kg/1 000 hooks; mostly Macrourus berglax, Raja hyperborea and Reinhardtius hippoglossoides. The abundance and vertical distribution of the fish on the continental slope are closely related to the hydrography of the Norwegian Sea. Atlantic water with temperature 5—7° C covers the edge of the shelf down to about 500 m while deep water of arctic origin with typical temperature -0.9° C is found along the slope in depths below 600—700 m. An inter- mediate, variable layer occurs between. Prospects of commercial utilization of the fish resources on the slope are discussed.