Aspects of the distribution and interannual variations in larval fish assemblages at South Georgia, Antarctica

The Antarctic fish fauna is relatively impoverished with fewer than 300 species recorded from the whole Southern Ocean. Demersal forms predominate but many of these have extended early life histories as pelagic larval and juvenile phases. Only 30 larval stages of the 103 fish species occurring at South Georgia have been identified but these represent all of the dominant and economically important forms. The larval stages occur in succession throughout the year suggesting niche separation to avoid competition. The ichthyoplankton distribution exhibits a marked division between oceanic and neritic coincident with the continental shelf-break. The neritic larval assemblages are more diverse and abundant with greater proximity to the coast. Studies on ichthyoplankton temporal distribution in the fjord, East Cumberland Bay, and the adjacent shelf areas at South Georgia show both large seasonal variations and marked interannual variations in species composition and abundance. The mechanisms controlling the larval fish assemblages are not known but the observed interannual variations must reflect interactions within the neritic ecosystem and so have important implications for subsequent recruitment at South Georgia. By-catch of young fish during the krill fishery further perturbate recruitment success and may delay the recovery of fish populations from over-exploitation by commerical-scale fin-fisheries over the past 30 years.