Copepod biomass, size composition and production in the Southern Benguela: spatio–temporal patterns of variation, and comparison with other eastern boundary upwelling systems

Zooplankton sampling has been conducted biannually off the west and south-west coasts of South Africa since 1988, as part of the pelagic fish stock assessment cruises covering the continental shelf (0–200 m). Previously established relationships between body mass and growth rate were used to derive copepod production. Mean copepod biomass and annual production in the Southern Benguela between 1988 and 2003 were 2.1 g C m-2 and 134.4 g C m-2 yr-1, respectively. Biomass and production were higher during summer in four latitudinal areas, but seasonal variability was only significant for the central West Coast. This area, lying downstream from the Cape Columbine upwelling cell, supported the highest levels of copepod biomass (3.1 g C m-2) and production (545 g C m-2 d-1). Production during winter, when upwelling is minimal, contributed over one third of annual production in all four areas. Copepod biomass, daily production and size composition varied with latitude, season and year, and there were no consistent trends in interannual variability over the study period. Although biomass in the four major EBUS was of the same magnitude (usually -2), annual production estimates are an order of magnitude greater than those made four decades ago, with highest values for the Southern Benguela