GEOGRAPHIC-VARIATION IN LOLIGO-FORBESI IN THE NORTHEAST ATLANTIC-OCEAN - ANALYSIS OF MORPHOMETRIC DATA AND TESTS OF CAUSAL HYPOTHESES

Geographic variation in the squid Loligo forbesi was investigated usin g multivariate analysis of morphometric and meristic characters in sam ples of squid taken from 13 localities in the Northeast Atlantic Ocean . Two character sets, body morphometrics and beak morphometrics, indic ated similar patterns of variation, with squid from the Azores differi ng markedly from those on the continental shelf. No consistent pattern was apparent in meristic data. Partial Mantel tests indicated that si milarity matrices for morphological data were significantly correlated with distance matrices for (a) geographic proximity, (b) whether the capture site was on the continental shelf or the Azorean bank, and (c) (beak data only) average sea-surface temperature at site of capture. Partial Mantel tests on allozyme data for the same individuals support hypothesis (b). The results suggest that L. forbesi in the Azores may reasonably be regarded as a distinct stock, differing significantly f rom L. forbesi on the continental shelf.