COPEPOD PRODUCTION IN THE SOUTHERN BENGUELA SYSTEM

Several methods have been used to indirectly estimate copepod producti on in the southern Benguela region, based on field sampling of copepod stages and laboratory measurements of growth and development rates un der variable food and temperature regimes. Estimates of production hav e steadily increased from 11 gC m(-2) y(-1) in 1979 to 80 gC m(-2) y(- 1) in 1987. Since 1988, extensive measurements of copepod egg producti on and moulting rates of Calanus agulhensis at sea during hydro-acoust ic fisheries surveys over the south and west coasts of South Africa in November have provided more direct estimates of copepod production. D aily Mean Production :Mean Biomass(P:B) ratios varied between 0.1 and 0.3 and annual production ranged between 17 and 150 gC m(-2) y(-1). Co pepod biomass, distribution, and demographic structure varied between cruises in different years, apparently linked to both the abundance of predators and shifts in hydrology. Production appeared to be due more to shifts in distribution of biomass and demography of Calanus than t o variations in growth rates. Poor correlations existed between juveni le growth and female egg production, suggesting one is unable to predi ct population growth from egg production rates only. Weak correlations between growth rates of different stages also suggest that the only m eaningful measure of copepod production requires all stages to be incu bated. (C) 1995 International Council for the Exploration of the Sea