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

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 Gre enland 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 variatio n in vertebral numbers is therefore suggested to be greater than the variat ion between sample areas. Despite the protracted egg and larval stage of Gr eenland halibut, the currents along the West Coast of Greenland are unlikel y to transport juveniles in any significant amount from the Davis Strait sp awning grounds to the North-west Greenland fjords. The origin of the northe rnmost populations therefore remains unknown. As single cohorts in the mate rial seem to affect the total average counts per area significantly it is s uggested that a change in the distribution of Greenland halibut might have occurred during the period studied. The results also emphasize the importan ce of relying on data based on more than one year and question the suitabil ity of vertebral counts in stock delineation studies of Greenland halibut. (C) 1999 International Council for the Exploration of the Sea.