DECAPOD LIFE-HISTORIES AND REPRODUCTIVE DYNAMICS IN RELATION TO OCEANOGRAPHY OFF SOUTHERN AFRICA

The reproductive dynamics of seven commercially important southern Afr ican decapod crustaceans are contrasted in terms of their lifetime egg production per recruit (E/R). Despite having very different larval li fe histories, both the shallow-water continental shelf spiny lobsters (Panulirus homarus rubellus and Jasus lalandii) and crab (Scylla serra ta) have substantially smaller eggs and higher values of egg per recru it than the deep-water spiny lobsters Palinurus delagoae and P. gilchr isti or the crab Chaceon maritae. A single shallow-water oceanic islan d spiny lobster (Jasus tristani) has similar egg characteristics (size and E/R values) to those of the deep-water lobsters. The hypothesis i s presented that large E/R values in the shallow-water spiny lobsters and crabs may be an evolutionary response to high rates of mortality o f larval and juvenile stages in the nearshore coastal environment. Sma ll size of eggs is considered to be an adaptation to allow for larger brood sizes and greater egg production in the shallow-water species.