MORPHOMETRIC VARIATION IN LOLIGO-FORBESI AND LOLIGO-VULGARIS - REGIONAL, SEASONAL, SEX, MATURITY AND WORKER DIFFERENCES

Morphometric variation in the squid Loligo forbesi was investigated to quantify effects of region, season, sex and maturity. Practical exerc ises were carried out using this species and the congeneric Loligo vul garis to evaluate differences in measurements by different workers. Th e utility of meristic characters was also examined. Consistent signifi cant differences were found between measurements by different workers, although this problem may be reduced with experience and many of the differences were small compared with observed differences between area s, particularly differences between Loligo forbesi from the Azores and elsewhere (Scotland, Spain, Portugal). Body shape in Loligo forbesi v aried significantly in relation to maturity stage and, to a lesser ext ent, with season. Multivariate analysis of morphometric characters for samples collected in Scottish waters over 12 months revealed no consi stent differences between localities. In contrast, there were marked d ifferences between Loligo forbesi from the Azores and those from UK wa ters. If future studies on geographic variation in loliginids are to m ake use of morphometric characters, they should be based on simultaneo us sampling to minimise effects of season and maturity, and all measur ements on a single character should be made by a single worker.