Pelagic occurrence of Greenland halibut (Reinhardtius hippoglossoides) studied by means of vertical longlines

Abstract

In order to calculate reliable survey indices it’s important to know the dynamics of vertical distribution of a fish species. The vertical distribution of Greenland halibut (Reinhardtius hippogolossoides) cannot be studied acoustically due to low acoustic contrast. Therefore a series of experiments were designed to catch the species pelagically in the Barents Sea. Sampling was made by means of vertical longlines during three time periods of the year. The paper presents preliminary results from the experiments. Catch-rates through the water column was analysed and population structure compared between demersal and pelagic samples. Stomachs from bottom trawls were analysed to identify pelagic prey. At 400-700 m bottom depth, individual Greenland halibut were caught up to 420 m off the bottom. Individuals of all sizes were caught pelagically, but catches were dominated by smaller males. Pelagic occurrence varied between sampling periods, being more important in August and December than in March. Still, pelagic prey were found in stomachs from all seasons.