Preliminary estimates of annual capelin consumption by Atlantic cod and Greenland halibut

Abstract

In order to obtain a fishery-independent index covering a significant portion of the Gulf of St. Lawrence (GSL, NAFO Divisions 4RST) capelin (Mallotus spp.) stock area, the stomach contents of Atlantic cod (Gadus morhua) and Greenland halibut (Reinhardtius hippoglossoides) collected during the summer nGSL multispecies survey were examined. Using a bioenergetics approach, it was estimated that annual capelin consumption by the two predators continued to be higher than the commercial landings recorded for the GSL. These results support those obtained from previously published ecosystem models. All length classes combined, the percentage of capelin in the mean stomach contents of Atlantic cod shows greater interannual variation compared to the stomach contents of Greenland halibut. The use of capelin by Greenland halibut more closely reflected changes in the average number of capelin caught per tow in the nGSL multispecies surveys in years for which fish stomachs were available. However, several sources of uncertainty were raised regarding the stomach content data used and some of the assumptions in the methodology, and the need to collect samples at other times of the year was pointed out. Since capelin is one of the major forage species in the GSL, considering the population patterns of its predators and assessing their consumption of capelin would be additional aspects of interest to include in the assessment of this species.