REPRODUCTIVE AND DISTRIBUTION PARAMETERS OF THE BLUE SHARK PRIONACE GLAUCA, ON THE BASIS OF ON-BOARD OBSERVATIONS AT SEA IN THE ATLANTIC, INDIAN AND PACIFIC OCEANS

On the basis of 81560 observations of Prionace glauca carried out on board surface longline vessels between 1993 and 2003 in the Atlantic, Indian and Pacific Oceans, the basic reproductive parameters of this species are presented. Thirty-five percent of the specimens observed were females, showing a clear prevalence of males in the catches. The identification of 28733 females allow us to provide sex ratio data, both overall and at size, as well as the prevalence of females on the basis of different signs of fecundation. The results revealed important differences between zones-regions in terms of sizes, CPUEs and sex ratios. Of the total number of females observed, 50.34 % showed signs of fecundation; of these 39.2 % were found to be gravid and 11.1 % exhibited mating injuries. Stages associated with reproduction were detected in most of the zones studied, although considerable differences were seen among zones-regions-seasons. The mean litter size was estimated to be 37.1 pups, with an average FL size of 19.7 cm, with levels of development depending on the region. The significance of the relationship between female size and litter size was determined (No. embryos =-61.605 + 0.470403*FL female), (P < 0.01). A significant relationship (P < 0.01) between the size of the embryos and month-zone predictor variables was also established into each region. The models fitted explain between 22.2 % and 71.7 % of the variability in embryo size, depending on the region under consideration