Early summer distribution of Antarctic krill sexual development in the Scotia-Weddell region: a multivariate approach

Summary The sexual Development of antarctic krill was studied during the EPOS leg 2 cruise (November 1988–January 1989) in the seasonally ice covered Scotia-Weddell Confluence area. Multiple Correspondence Analysis (MCA) was used to elucidate the general trends of variation of biological (body-size, molt stage) and environmental data (geographical position, sea-ice extension, sampling time) associated with female development. In November, female krill from the ice covered area (Weddell Sea) had a juvenile ovary, while pelagic female krill from Scotia Sea were in advanced previtellogenesis, and one third of them had already spawned. The successive samples from the Confluence illustrated a rapid advance of sexual development during the whole period. Both observation of live krill maintained on board and the MCA confirmed the general trend of distribution of sexual development in relation with size structure and environmental factors. Previtellogenesis occurs in relation with the ice-edge, while vitellogenesis is performed in short cycles in the summer pelagic habitat. The degree of sexual development attained by krill samples (measured by the sexual development index, SDI) is then a good indicator of the biological activity of the krill population and of its impact on the pelagic ecosystem.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation