Spatio-temporal variations in reproductive patterns and population structure of Pasiphaea multidentata (Decapoda: Caridea) in the Blanes canyon and adjacent margin, North-western Mediterranean Sea

Pasiphaea multidentata is a deep-water caridean shrimp fished in the Mediterranean in association with the commercially exploited red-shrimp Aristeus antennatus. A previous study describes seasonality in the reproductive pattern of P. multidentata using external morphological parametres. This study assesses the spatio-temporal variations in the population structure, sex ratio, ovary cycle and gametogenesis of P. multidentata from three different fishing grounds in the Blanes canyon and adjacent margin (North-western Mediterranean) over an annual cycle. The oogenetic pattern of this species is typical of a caridean shrimp. There is a pool of previtellogenic oocytes at all times that develop from the periphery of the gonad towards the centre during maturation. Previtellogenic oocytes grow to approximately 200 ?m before undergoing vitellogenesis. The vitellogenic oocytes are surrounded by a monolayer of accessory cells. The maximum size observed for a mature oocyte was 1420 ?m. The oocyte-size distribution confirmed the seasonal reproductive pattern of this species; in winter, the ovaries contained mainly previtellogenic oocytes, some of which start maturing in spring, resulting in a slightly bimodal distribution. In summer, the vitellogenic oocytes reach approximately 1000 ?m and in late autumn the ovaries are fully mature and ready to spawn. There were no significant differences in the reproductive and population structure patterns of P. multidentata among the three sites, suggesting that the population’s distribution is not affected by the geomorphology of the area, in particular the presence of the canyon. The populations are dominated by females at all sites and all seasons, with the arrival of juveniles in spring. The seasonal variations in the reproduction and recruitment of P. multidentata and the lack of spatial segregation within the population are discussed in terms of the species’ known biology, the effects of canyons in energy supply to the deep-sea floor and the relationships of this species with the red-shrimp A. antennatus.