Discriminant analysis of geographic variation in hard structures of Todarodes sagittatus from the North Atlantic

Discriminant function analysis was applied to the morphometries of the ommastrephid squid Todarodes sagittatus (Lamarck 1798) in an attempt (1) to discriminate possible differences in the morphometric characteristics of groups from different geographic locations; (2) to elucidate the possible use of cephalopod hard structure morphometries to identify populations; and (3) to determine which of the morphometric characteristics are the most significant in this respect. A total of 27 morphometric characters were measured using the bodies, arms, gladii, beaks, and statoliths of specimens caught off northern Norway, Scotland and Portugal. Statistically significant differences were shown to exist among the three geographic areas, indicating the possible presence of different populations of T. sagittatus in the Northeast Atlantic. The results demonstrate the usefulness of hard structure morphometries as a tool for analysing variation within species.