Some information on the biology of Illex coindetii Verany, 1839 (Cephalopoda, Ommastrephidae) in the South-Western Adriatic Sea (Central Mediterranean)

Distribution, length frequency structure, sex-ratio, maturity and dorsal mantle length–total weight relationship for Illex coindetii (Verany, 1839) were described for the first time in the South-Western Adriatic Sea (Central Mediterranean). Samples came from six experimental bottom trawl surveys carried out within the framework of the Medits programme from 1997 to 2002. Although specimens have been collected at a wide depth range, I. coindetii concentrates between 50 and 200 m. The population had a smaller squid size and length at first maturity with respect to other Mediterranean and Atlantic regions, probably due to the interaction of some environmental factors (sea temperature and fishing pressure) and the biological characteristics of the species. There was no difference in males/females ratio by year, but there was a general dominance of females over males at larger sizes and of males over females at smaller sizes. The different proportion of juveniles and mature individuals in the catch suggested the possibility of a prolonged spawning season with a spring spawning peak. There was a pronounced sexual dimorphism, females mature at larger mantle length attaining larger size in respect of males. Length–weight relationship revealed a difference between sexes in maturing and mature individuals only, with males resulting heavier and more robust than females at the same size. There were no differences in body proportions between unsexed and immature individuals of both sexes, which were considerably slimmer than maturing and mature counterparts.