Condition and Feeding of Greenland Halibut (Reinhardtius hippoglossoides) in the North Atlantic with Emphasis on the Flemish Cap

Abstract

The Relative Condition Factor of Greenland halibut (Reinhardtius hippoglossoides) was analysed for seasonal, annual and geographical variability. Sampling covered commercial fishing and scientific surveys in three areas of the North Atlantic (NAFO Divisions 3M and 3LNO, and ICES Division IIb), comprising a total of 64 984 individuals from 1992 to 2003. Several data sets were established in order to carry out the comparisons: individuals as a whole; by sex females and males separately; and by areas each area independently. Condition showed significant differences with regard to the area, season, size range and sex, but it was not always significant among interactions of these factors. Individuals from the Northeast Atlantic had better condition, while those in the Northwest Atlantic suffered a notable fall in condition throughout the studied period, mainly in Flemish Cap. Condition was lightly superior in females, regarding size. A clear increment in the feeding intensity appeared when the condition diminished. When the total weight is used to calculate the condition, more remarkable differences could be expected because this index is sensitive to the gonad weight; in this respect, adult females showed more marked differences. Moreover, the complex maturity schedule and variable maturity at size would contribute to find misleading differences. Feeding habits of Greenland halibut were studied in the same areas based on a sample of 19 001 fish. Feeding intensity was the higher on the Flemish Cap, where the main preys were Pandalus borealis, Sebastes spp. and Serrivomer beani. P. borealis predation increased in the late 1990s. Diet was piscivorous in Div. 3LNO and Div. IIb as well, mainly based on Mallotus villosus and Micromesistius poutassou, respectively. Cannibalism and offal consumption was remarkable in Svalbard (ICES Div. IIb). Fish predation increased when predator size increased. Molluscs took an important place in the diet of intermediate sizes in Div. 3LNO and IIb. Similar diet pattern for both sexes was observed.