Fiskeriundersøkelser ved Bjørnøya, Spitsbergen og i Barentshavet 1. - 27. juni 1971

Abstract

Distribution and abundance of the commercial important species in the investigated area were observed. Special attention was paid to the prerecruits of cod, haddock and redfish. Polar cod and capelin were also studied. The acoustic instruments were continuously used. Trawling with bottom and pelagic trawls was carried out for fish sampling and identification of echo recordings. A low abundance of the 1970 year-class of cod was observed and the abundance was lower than that observed for the 1969 year-class. These findings disagree with observations made during the International 0-group fish surveys in August—September 1969 and 1970 and during a Norwegian survey in November 1970. Three factors are considered responsible for these unexpected observations. I: A part of the 1970 year-class might in June 1971 have been living together with capelin in the upper 100 to 150 m, and the abundance might therefore have been underestimated. 2: Some part of the year-class might during the autumn and early winter 1970 — 1971 have been transported outside the investigated area. 3: The abundance of the year-class might during the winter 1970—1971 have been reduced by an unusual high natural mortality. Prerecruits of cod and haddock and the youngest prerecruits of redfish were in June recorded both near the bottom and pelagic. It could not be classified if this distribution reflects a vertical diurnal migration, but this type of migrations is established during late autumn and late winter for prerecruits. June might therefore not be a very suitable time to observe the abundance of prerecruits.