Density and size of reef fishes in and around a temperate marine reserve

Abstract

The effects of marine reserve protection on the density, size, biomass, sex-ratio and overall assemblage structure of reef fishes were investigated at Kingston Reef Sanctuary, Rottnest Island, Western Australia. Significant trends in response to reserve protection were found for two species of top predators and several serially protogynous labrid species. The relative density and biomass of the heavily targeted Glaucosoma hebraicum was 10 and five times greater within the sanctuary respectively. Similarly, the biomass of the serranid, Epinephelides armatus, was 3.2 times greater in the sanctuary, although this difference was owing to a greater mean length not relative density. The male : female sex ratio for the labrid, Ophthalmolepis lineolatus, was significantly different between sanctuary and non-sanctuary sites, with the density of male O. lineolatus significantly greater within the sanctuary. Rottnest Island waters are largely restricted to recreational fishing, therefore these results suggest that a range of fish species around Rottnest Island are affected by recreational fishing, and that these effects are found in taxa beyond the primary target species. The patterns in the effects on bycatch species suggest that fishing-related mortality may be exerting a greater control on these populations than that exerted by natural predation.