Population structure, growth and production of the surf clam Donax serra (Bivalvia, Donacidae) on two Namibian sandy beaches

Abstract

Population structure, growth and production of the surf clam Donax serra (Bivalvia, Donacidae), inhabiting highly exposed sandy beaches of Namibia, were investigated between November 1997 and December 1999. From length–frequency distribution and tagging–recapture data, a von Bertalanffy growth function with an asymptotic length ( L ∞ ) of 82 mm and a growth constant ( K) of 0.274 yr −1 was established. Regarding growth performance of Donacidae, D. serra fits in a group of species inhabiting cold temperate and upwelling regions. The intertidal biomass of the studied population ranged between 141 and 546 g ash-free dry mass (AFDM) m −2 yr −1. Individual production was maximal at 56.5 mm shell length (0.83 g AFDM ind. −1 yr −1), and annual production ranged between 167 and 637 g AFDM m −2 yr −1, resulting in productivity values (P/ B ̄ ) between 1.167 and 1.589 yr −1. These data underline the importance of D. serra for the beach/surf ecosystem. Further, the findings of this study are crucial to support future aquaculture or exploitation activities and management.