Assessment of estuary dependency and management of two important fishery species

The dependency on critical habitats, such as estuaries, represents a bottleneck in the life-history of many exploited fishery species. The proposed project aims to assess the management implications of estuarine dependency in two important South African c oastal fishery species, spotted grunter (Pomadasys commersonnii) and dusky kob (Argyrosomus japonicus). The poor stock status of both species has been ascribed, in part, to the overexploitation of juveniles during their obligatory dependence on estuarine habitats. A rational management plan for these species cannot be developed without explicit information on their movement patterns and ontogenetic use of estuaries. Despite heavy exploitation of juveniles within estuaries, the same stocks also support co astal and marine fisheries. Therefore, successful management for these species relies on knowledge of their dispersal characteristics, migrations between estuaries and the sea, and the possible movements between neighbouring, nearby and/or other estuaries . This study will assess ontogenetic changes in habitat use and the movement patterns of individuals between their natal estuary, other estuaries and coastal areas, using otolith microchemistry and acoustic telemetry methods. The results will provide imp roved knowledge on two of South Africa's most data-deficient fisheries, namely estuarine and subsistence fisheries, and be used to (i) evaluate the role of single estuaries in the production and export of juveniles to coastal fisheries, (ii) evaluate the role of protected areas as a management option to assist with restoring spawner stock biomass levels, (iii) develop an appropriate management procedure to ensure sustainability, and (iv) form the scientific basis for capacity building and education of stu dents. The project promotes capacity building, equity redress and research excellence through collaboration during fieldwork and publication of project results.