The suitability of vertebral counts in stock delineation studies of Greenland halibut, Reinhardtius hippoglossoides (Walbaum), in West Greenland

Abstract

Vertebral counts of Greenland halibut collected from West Greenland in 1995 were compared to samples from the same areas for the period 1987-1989. The 1995 samples, obtained in Davis Strait, Baffin Bay, and two North-west Greenland fjords, showed no significant differences in mean vertebral numbers. Previous studies in 1987-1989, however, showed significant differences in mean vertebral counts between some of the same areas. Inter-annual variation in vertebral numbers is therefore suggested to be greater than the variation between sample areas. Despite the protracted egg and larval stage of Greenland halibut, the currents along the West Coast of Greenland are unlikely to transport juveniles in any significant amount from the Davis Strait spawning grounds to the North-west Greenland fjords. The origin of the northernmost populations therefore remains unknown. As single cohorts in the material seem to affect the total average counts per area significantly it is suggested that a change in the distribution of Greenland halibut might have occurred during the period studied. The results also emphasize the importance of relying on data based on more than one year and question the suitability of vertebral counts in stock delineation studies of Greenland halibut.