Biological variation of Loligo vulgaris (Cephalopoda: Loliginidae) in the eastern Atlantic and Mediterranean

Abstract

The biological characteristics of the squid Loligo vulgaris from north France, northwest Portugal, the Saharan Bank, and the Greek Seas were analyzed to describe large-scale biological patterns and to evaluate geographical variation in the Atlantic and the Mediterranean. In northwest Portugal and on the Saharan Bank population length structures are more complex due to extended spawning and recruitment periods. Squid spawn only between November and April in north France and the Greek Seas. Gonadosomatic indices decreased with decreasing latitude in the Atlantic, while the highest indices were found in the Mediterranean. Full maturity occurred at smaller size in northwest Portugal than in other areas of the Atlantic, and at similar size to Mediterranean squid. Length-weight relationship slopes increased from the north to the south in the Atlantic and in the Mediterranean. Multivariate analysis of seasonal biological indices demonstrated significant biological differences between squid of different areas, mainly in terms of size at maturity, male GSI and average body size and weight. Biological variability between areas was considered related to plasticity of responses to large-scale geographic environmental conditions.