The Olhao artificial reef system (south Portugal): Fish assemblages and fishing yield

Since 1989 the Portuguese institute of Marine Research (IPIMAR) has been developing an artificial reef systems pilot project. The artificial reef system consists of a protection reef and an exploitation reef. As part of this project, a fishing survey was carried out over four and a half years, using gill nets. To test artificial reef effectiveness in enhancing fish assemblages and yield, a total of 72 catch operations were made. The fishing yields (weight) from the reefs exceeded those from the control sites, by 2.03 times for the protection reef, and by 1.11 times for the exploitation reef. Artificial reef deployment resulted in an enrichment and diversification of the local fish community, with an increase in the total species richness, mean species richness and the species diversity indices. Since the artificial reefs improved the local fishing yields and made possible a better use of the Ria Formosa 'nursery potential', the reefs appear to represent a useful management tool on the Algarve coast, contributing to the improved value of the artisanal fishery, which has a very important role in this region. (C) 1997 Elsevier Science B.V.