Distribution Patterns and Migration of Lithodes-Ferox (filhol) (anomura, Lithodidae) Off Namibia

Lithodes ferox (Filhol) is a deep water anomuran crab that inhabits the upper continental slope (300-1,000 m) off West Africa. The distribution and patterns of abundance of this species have been studied based on demersal fishery research data. The study revealed the occurrence of a seasonal bathymetric migration. The species rarely occurs at depths less than 400 m in summer, while there is a dispersion of the population towards shallower waters (up to around 300 m) in winter. These movements appear to be mainly related to the reproductive biology of the species (ovigerous females account for most females in winter in the shallowest stratum) as well as to upwelling-related seasonal decreases of oxygen levels on the bottom. Recruitment to the adult population takes place in deep water. Juvenile crabs are found almost exclusively in areas deeper than those inhabited by the adult population. Sex-ratio distribution shows a clear tendency for the species to form unisexual groups. Males tend to be captured with other males and females with other females.