The Northeast Arctic cod stock's consumption of commercially exploited prey species in 1984- 1986

Abstract

In order to evaluate the growing influence of Northeast Arctic cod (Gadus morhua) on some commercially exploited prey species, the annual consumption of these species by the cod stock has been estimated for 1984-1986. The estimates are based on stomach content weights and composition data from more than 11 000 cod sampled throughout the area of distribution at different times of the year, temperaturecorrelated digestion times from the North Sea, the number of cod in each age group during the years in question, and the geographical distribution of each group. The main prey species during the period was capelin (Mallotus villosus), and in 1985 the consumption approached two million tonnes, while in 1986 it was less than half of this. The next most important prey was deep-sea shrimp (Pandalus borealis), the consumption of which dropped from about 0.6 million tonnes in 1984 to below 0.3 million tonnes in 1986. Measured in numbers consumed, there was also a considerable consumption of young redfish (Sebastes spp.) and herring (Clupea harengus), and in the last years also of young cod and haddock (Melanogrammus aeglefinus). The results show that the growing cod stock has had a great impact on some of the commercially exploited prey species in 1984-1986, and some year classes may have been seriously reduced by this predation.