Reproductive patterns and fecundity of the NW Mediterranean deep-sea fish community

Abstract

The description of reproductive strategies and fecundity of fish has an important relevance in the study of their biology and population dynamics. However, our knowledge of the reproductive capacity of deep-sea fish is still very poor. Production of eggs is an energy-demanding process and, thus, a shortfall in food supply may cause a decrease in fecundity and/or egg size. Continental slopes are transitional environments between the shelf and deep basins, with strong gradients in pressure, temperature, food supply and light. Therefore, the study of fecundity and egg size of fish along the continental slope can provide important data to better understand the modulation of reproductive capacity. The fish community of the Catalan margin (northwestern Mediterranean) was sampled between 400 and 2700 m depth. The gonads of 2672 individuals from 13 different species were analyzed macroscopically to determine sex and maturity stage. The mature ovaries of a subsample of 300 individuals were dissected out for histological and image analyses. The oocyte-size distribution patterns show that all species analyzed present group synchronous ovarian organization. Total fecundity and egg size were quantified for the first time for the 13 species considered. The results were compared with previous published data on shallow-water and Atlantic species. Preliminary results showed a pattern of decreased fecundity with depth. Fecundity and egg sizes were lower in Mediterranean species compared to congeneric species in the Atlantic Ocean as reported in the literature. The results are discussed in relation to environmental characteristics