Natural fishing experiments in marine reserves 1983-1993: community and trophic responses

This study examined the effect of fishing on the density, biomass, species richness and overall structure of the reef fish community at two islands (S umilon and Ape) in the Philippines from 1983 to 1993. A series of natural f ishing experiments over this period involving marine reserves were monitore d at each island, where estimates of fishing intensity and selectivity were available. Fishing intensity (15% and 25% of biomass removed per year at S umilon and Ape, respectively) was high enough to affect total community bio mass, but not density, significantly. Species richness was not affected sig nificantly by fishing, except at Sumilon reserve. The fishery was relativel y non-selective with most families/trophic groups caught roughly in proport ion to their contribution to community biomass. Thus fishing did not alter the relative abundance of the major families/trophic groups significantly, except during a period of use of explosives and drive nets in the Sumilon r eserve. At the level of family/trophic group the community displayed strong resilience of structure. There was little evidence of secondary effects e. g, declines in abundance of large predators resulting in measurable increas es in abundance of their prey. This resilience of the community to the effe cts of fishing most likely results from three important community attribute s (open nature of the component populations, likely maintenance of upstream recruitment supply and apparent lack of any obvious "keystone" species or families) and one important characteristic of the fishery (relatively non-s elective with respect to the components of the community).