Distribution and movement patterns of white musselcracker Sparodon durbanensis, a South African endemic seabream

Abstract

The white musselcracker Sparodon durbanensis (family Sparidae) is a highly prized shore angling and spearfishing species. This study investigated its movement behaviour along the southeastern seaboard of South Africa, using tag-recapture data. A total of 3 378 S. durbanensis were tagged between 1984 and 2023 as part of the Oceanographic Research Institute’s Cooperative Fish Tagging Project. Fish were tagged throughout their distribution range, although peaks in tagging effort occurred in the De Hoop and Tsitsikamma marine protected areas. Of the fish tagged, 99 individuals (2.9%) were recaptured. Two thirds (66.7%) of all recaptures were made within 5 km of their release site, whereas the remaining 33.3% showed ranging movements of between 5 and 843 km. Juveniles were highly resident, whereas adults showed a greater tendency to move farther, which increased significantly with increasing time at liberty. Adults moved significantly more in a northeasterly direction, and there was a tendency for fish to move northeastward in winter and southwestward in summer, suggesting the possibility of a northeastward seasonal spawning migration. There was some evidence of seasonality in the catches, with the greatest numbers of S. durbanensis being caught between September and December during the spawning season. However, there was no clear evidence that the catches varied spatially with season. We recommend that further research be undertaken on the spatio-temporal patterns of juvenile recruitment and dispersal, as well as the movement behaviour of adults, by using acoustic telemetry to determine whether spawning migrations take place and where prime spawning areas are located. Improving our understanding of the spatio-temporal patterns of this species’ spawning migration and aggregations will help improve conservation measures for this endemic seabream.