The relationship of reef fish densities to the proximity of mangrove and seagrass nurseries

Abstract

Visual census surveys were used to study the distribution of coral reef fishes that are associated with seagrass beds and mangroves in their juvenile phase, on various coral reef sites along the coast of the Caribbean island of Curaçao (Netherlands Antilles). The hypothesis tested was that various reef fish species occur in higher densities on coral reefs adjacent to nursery habitats than on reefs located at some distance to these habitats. Of 17 coral reef fish species that are known to use bays with seagrass beds and mangroves as nurseries (nursery species), 15 were observed in quadrats on the reef. Four nursery species, Haemulon sciurus, Lutjanus apodus, Ocyurus chrysurus and Scarus coeruleus occurred in significantly higher densities on coral reefs adjacent to bays with seagrass beds and mangroves. Lutjanus analis, Lutjanus mahogoni and Sphyraena barracuda also had their highest densities on reefs adjacent to these bays, although differences between the distinguished reef categories were not always significant. It is suggested that these seven species are highly dependent on the presence of bays with seagrass beds and mangroves as nurseries on an island scale. Eight other species that are known to use seagrass beds and mangroves as nurseries did not have their highest densities on reefs adjacent to bays with seagrass beds and mangroves. For six of these species, juveniles were also observed on the reef. It is suggested that these species are able to use the reef as an alternative nursery and do not depend strictly on the presence of bays with seagrass beds and mangroves as nurseries.