Anchovy distribution off Namibia deduced from acoustic surveys with an interpretation of migration by adults and recruits

Abstract

Qualitative acoustic surveys of the anchovy Engraulis capensis off Namibia were undertaken between 1978/79 and 1985. Near-monthly maps of shoal distribution are presented for each year which covered the summer spawning and the winter feeding seasons. Distribution densities are ranked according to three selected grades. The data are discussed in relation to the oceanography of the region as well as to previously documented spawning and larval distributions. Conclusions are drawn which may help in understanding the migration patterns of anchovy off Namibia. Adults occupy winter feeding grounds in the north and move out to the spawning grounds between the Cunene River and Hollams Bird Island in summer. Post-larvae are transported passively to the nursery areas where they feed and develop. Juveniles move north in autumn to the preferred feeding grounds around Walvis Bay, where they enter the fishery as recruits in winter. At the end of winter, they join the adults in the north. The inferred pattern would be advantageous to both feeding adults and juvenile anchovy, while also avoiding competition between the two components for food resources. This fits classical theory, but there are limitations to the data. © 1990 Taylor and Francis Group, LLC.