Evidence of a biomass hotspot for targeted fish species within Namena Marine Reserve, Fiji

Abstract

Namena is Fiji’s oldest and second largest no-take marine reserve, and has relatively high abundance and biomass of targeted fishes within its boundaries due to a high level of protection since its creation in 1997 (formalised in 2005). Following anecdotal reports of exceptionally high fish abundance at the Grand Central Station dive site within Namena, we conducted a 500-m meandering diver-operated video transect along the main reef formation, to obtain abundance, length and biomass estimates for fish species targeted by local fishers. Our census revealed extremely high diversity, abundance and biomass (11436kgha−1) of targeted fishes. While demersal reef fishes were present at higher densities than on typical fished reefs in the region, they were dwarfed by aggregations of reef-associated pelagics, namely the barracuda Sphyraena forsteri (5540kgha−1) and the trevally Caranx sexfasciatus (4448kgha−1). These estimates are comparable to those of historically unfished or ‘pristine’ locations, an unexpected finding given the historical fishing pressure within the reserve before its establishment and ongoing pressure in surrounding fished areas. This finding presents Grand Central Station as a useful reference site for ecologists and managers, and highlights the ability of protected coral reefs to support or attract very high densities of fish.