Long-term trends in catch and effort in the KwaZulu-Natal nearshore linefisheries

• Published in: South African journal of marine science 1999-06, Vol.21 (1), p.51-76
• Main Authors: Penney, A. J., Mann-Lang, J. B., van der Elst, R. P., Wilke, C. G.
• Format: Article
• Language: English
• Subjects: Argyrosomus; Atractoscion aequidens; Cheimerius nufar; Chrysoblephus puniceus; Epinephelus; Petrus rupestris; Polysteganus coeruleopunctatus; Polysteganus undulosus; Scomberomorus commerson
• ISSN: 0257-7615
• DOI: 10.2989/025776199784125890

The boat-based linefishery is the most important marine fishery along the coast of KwaZulu-Natal, producing 40% of the total annual mass of fish landed there. Since 1900, the fishery has supported commercial and recreational sectors that compete for more than 120 species, using similar methods in the same fishing areas. Catch-and-effort data have been collected sporadically from the commercial linefishery since 1910 and the recreational linefishery since 1970. The number of commercial vessels increased from 10 in 1910 to 140 in 1995, and effective commercial effort continues to increase, despite a limit placed on the number of vessels in 1985. Recreational participation escalated from 20 skiboats in 1948 to 2 000 in 1995 and entry to this sector remains unlimited. Introduction of the beach-launched, trailable skiboat in 1945 resulted in a rapid expansion of effort to coastal areas that previously functioned as harvest refugia for resident reef fish. Total catch has declined, despite increased effort, as has catch per unit effort (cpue) There have also been substantial changes in catch composition and catches have been sustained by sequential target switching from large endemic reef fish such as seventyfour Polysteganus undulosus, red steenbras Petrus rupestris and rockcods Epinephelus spp., to smaller sparids. such as slinger Chrysoblephus puniceus, santer Cheimerius nufar and blueskin Polysteganus coeruleopunctatus, and shoaling migrants, such as king mackerel Scomberomorus commerson, geelbek Atractoscion aequidens and kobs Argyrosomus spp. The linefish resources off KwaZulu-Natal have long been incapable of sustaining the fishing effort in the region and most resident species are now overexploited. Existing linefish management measures have not been successful in limiting fishing mortality to sustainable levels and existing limits on commercial permits and recreational launches will have to be substantially reduced if this is to be achieved. Bag limits may also have to be substantially reduced, particularly for endemic reef fish, to rebuild stocks to sustainable levels. Given the difficulty of implementing such controls, the maintenance of a number of large, suitably sited marine reserves appears to offer one of the few practicable chances of conserving the endemic reef fish stocks of KwaZulu-Natal.