Reproduction and recruitment patterns of the surf clam Donax serra (Bivalvia, Donacidae) on two Namibian sandy beaches

Abstract

Reproduction and recruitment of the surf clam Donax serra on two Namibian beaches were studied over a period of two years. Histological examination of the gonads indicated a discontinous annual reproductive cycle, related to monthly mean sea surface temperature. The spawning season lasted from August/September to February, but juveniles (2–6 mm anterior-posterior shell length) were only present for three months in the intertidal zone. The condition index indicates that the species spawns during autumn and summer, but histological validation is needed. The period when juveniles are abundant is decoupled from the spawning period and therefore cannot be predicted clearly, even if the spawning period is known. Starvation, hydrodynamic processes, chemical parameters and different release times during the spawning period are thought to cause the differences in settlement time and recruitment strength between locations.

Keywords: condition index, Donax serra, histology, Namibia, recruitment, reproduction, sandy beach ecology

African Journal of Marine Science 2001, 23: 53–60