The effect of marine protected areas on an exploited population of sex-changing temperate reef fish: an individual-based model

  • SE Kerwath Marine and Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa
  • A Götz Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
  • CG Attwood Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
  • WHH Sauer Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa

Abstract

The effect of two marine protected areas (MPAs) on roman Chrysoblephus laticeps (Sparidae), an exploited reef-fish species inhabiting the South African temperate south coast, was simulated with a spatially explicit, individual-based model based on geographically correct habitat distribution. The model domains were small compared with the dispersal range of pre-recruits, and recruitment was held constant. Adult fish movement rules were based on the results of high-resolution markand-recapture and telemetry studies. Fish densities, age-structure and life-history parameters were derived from comprehensive underwater surveys and biological analyses. The model included the effect of fishing on size-at-sex change. The results indicate a recovery of fish abundance-per-recruit, size frequency and sex ratio to, or close to, pre-exploitation levels within the protected areas 10 years after the implementation of both MPAs. Results suggest that, for resident species such as roman, even small MPAs (6 km2) can offer protection. The small exchange of post-recruit fish into the adjacent areas results in negligible improvement (1%) of catches. The MPAs support more and larger spawning fish, which may improve recruitment into adjacent fished areas.

Keywords: Chrysoblephus laticeps; fisheries management; individual-based model; marine protected areas; South Africa, spillover

African Journal of Marine Science 2008, 30(2): 337–350
Published
2008-10-20
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X