Life-history styles of eight morphologically similar estuary-associated sparid species from southern Africa

Abstract

This review explores the similarities and differences in the life-history styles of eight morphologically similar sparid species that occupy the nearshore coastal waters around South Africa. All eight species spawn at sea with two taxa, Acanthopagrus vagus and Rhabdosargus holubi, being dependent on estuaries as primary nursery areas. Two of the species, Rhabdosargus globiceps and Rhabdosargus sarba, have a high proportion of their juveniles in estuaries but are not completely dependent on these systems as nurseries. The remaining four species, Rhabdosargus thorpei, Diplodus capensis, Diplodus hottentotus and Sarpa salpa, have a major proportion of their juveniles on the coastal shelf, with only a small percentage in estuaries. Four of the species (D. capensis, D. hottentotus, R. holubi and S. salpa) occur in all four biogeographic regions, three (A. vagus, R. sarba and R. thorpei) are primarily found in the tropical and subtropical waters and one species (R. globiceps) primarily in temperate areas. All eight species have relatively fast growth rates and a small size at reproductive maturity when compared to other larger sparids, which occupy offshore reef systems and are not found in South African estuaries at any stage of their life cycle. By adopting different life-history styles, the fishes belonging to the family Sparidae have successfully colonised all South African estuaries and the adjacent coastal shelf waters in all four marine biogeographic provinces and are ranked as a dominant marine fish family in terms of both number and biomass in estuaries on the subcontinent.