Using landscape ecology to describe habitat connectivity for coral reef fishes.

摘要

Some coral reef fishes depend on specific habitats to complete ontogenetic migrations. The distribution of these nursery species may be influenced by the connectivity between nursery habitats, used during early life stages, and coral reefs. The lack of nursery habitats can potentially limit the development or presence of fish populations depending on the nature of the fish-habitat relationships. Mangroves and seagrasses have been shown to support the ecological nursery function; therefore the lack of mangroves at a remote oceanic island (Mona, Puerto Rico) presents an opportunity to explore habitat connectivity at the island scale. Landscape composition and habitat configuration were tested to explain the presence and abundance of ontogenetic stages of reef fishes. Mona Island's insular shelf was sampled by quantifying habitat metrics and fishes in 613, randomly stratified belt-transects (60 m 2). Nursery habitats (nearshore seagrass, hardbottom (bedrock), coral reef) were species-specific and cross-shelf ontogenetic migrations were identified for the coral reef fish assemblage. When compared to La Parguera (with abundant mangroves and seagrass), the presence and abundance of some species at Mona were limited. A notable exception was Lutjanus apodus, which occupied nearshore hardbottom at Mona during juvenile stages. Habitat metrics correlated with fish density at distinct spatial scales and varied between species, suggesting ontogenetic requirements are species-specific and scale dependent. Depth, substratum vertical relief as well as percent cover of some epibenthic groups were important correlates to fish abundance for the different ontogenetic stages. At landscape scales, areas with small patches (∼100 m2) of coral habitat located in proximity to each other supported higher fish densities, although their arrangement on the shelf influenced this relationship. The distribution and replication of key habitats within Mona Island's marine reserve suggest that this protection is sufficient to encompass inter-habitat connectivity for reef fishes. However, the limited distribution of nursery habitat in nearshore areas implies that land-based threats may present greater potential impacts to juvenile fishes. Landscape ecology served to detect patterns of habitat use and ontogenetic connectivity of reef fishes applicable to evaluating the ecological value of a particular arrangement of habitats within spatial-based protection.