The reproductive biology of Diplodus sargus capensis and D-cervinus hottentotus (Sparidae) off the south-east Cape coast, South Africa

An investigation of the reproductive biology of Diplodus sargus capensis and D. cervinus hottentotus was undertaken in the Tsitsikamma National Park, South Africa. Gonado-somatic indices showed that both Diplodus species had protracted spawning seasons extending from early spring into summer. The adult sex ratio of D. s. capensis was significantly dominated by females while that of D. c. hottentotus showed no significant difference from a 1:1 sex ratio. Size at 50% maturity was calculated at 211 mm FL and 280 mm FL for D. s. capensis and D. c. hottentotus respectively. This corresponded to an age of three and six years respectively. A detailed histological examination of gonad development revealed that D. s. capensis is a digynous hermaphrodite with partial protandry occurring in some of the male population. D. c. hottentotus is shown to be a rudimentary hermaphrodite. Group spawning behaviour in bath species is postulated based on various morphological and indirect behavioural characteristics.