The squid Todarodes sagittatus (Lamark) : Distribution and biology in northern waters, April 1980 - April 1981

Abstract

Durinq the summerer and autumn of 1980 the squid Todarodes sagittatus invaded the Norwegian Sea and adjacent areas in great quantities. The invasion may partly be connected with an increased influx of Atlantic water, as indicated by considerable numbers of salps. Materials for investigation were collected from April 1980 to April 1981 in northeast Atlantic waters, the North Sea, the Norwegian Sea, and in the coastal waters of Norway. The mean dorsal mantle length (DML) increased from 16-18 cm for both sexes in April 1980 to 31-32 cm (males) and to 35-38 cm (females) in December, and further to 33 cm and 40 cm respectively in March 1981. Weight-length relations were calculated for various size groups. Growth curves were fitted to the length-frequency data, applying the von Bertalanffy equation L(t) = Loo (1 - exp[-k(t-to)]). The liver weight varied from 4% to 17% of the total weight, average figures from 6.7% to 10.9%. Males constituted from 0% to 10% of the samples in coastal areas, in open waters, 20-28%. Food consisted mainly of fish, followed by cephalopods, euphausids and amphipods. In coastal areas T. sagittatus is supposed to eat a lot of 0-group fish. Age readings of daily rings in the statoliths indicate a life cycle of 1-1½ years. Most of the squid investigated were 6-11 months old. Behaviour of squid was studied using echo sounders and underwater TV cameras. The Norwegian squid fishery yielded 2.500 metric tons in 1980.