Seasonal trends in sea surface temperature, dry mass per oocyte and batch fecundity of pilchard Sardinops ocellatus in the northern Benguela system

Abstract

The study was aimed at establishing whether there was a relationship between seasonal trends in sea surface temperature (SST) on the spawning grounds and the dry mass of hydrating oocytes and batch fecundity of pilchard Sardinops ocellatus in the northern Benguela ecosystem. Environmental and biological data were collected during the period June 1972–October 1974. There was a clear seasonal cycle in SST on the spawning grounds, with temperatures at their lowest in winter/spring and peaking during summer/autumn. Oocytes were heavier in winter/spring than in summer/autumn, showing a significant inverse correlation with the ambient sea surface temperature. Dry mass per oocyte was neither related to size of fish nor inversely related to batch fecundity. There was no specific relationship between batch fecundity and temperature, both high and low levels of batch fecundity being found in each environmental regime.