Alternate Title

A Comparison of Fish Assemblages Among Five Habitat Types Within a Caribbean Lagoonal System

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Fish assemblages associated with patch reefs, rubble, seagrass, algal plain, and sandy habitats types were studied at St. Croix's Southeastern barrier reef lagoon using underwater visual census techniques. Higher species richness and fish density were observed over patch reefs/rubble habitat followed by seagrass, algal plain, and unvegetated sandy habitat types. Thalassoma bifasciatum, Haemulon flavolineatum, and Acanthuras chirurgus were the most common fishes in highly structured habitat types (patch reef, rubble). Halichoeres bivittatus, Sparisoma radians, newly settled grunts (l.e., Haemulon spp.), and juveniles of Ocyurus chrysurus were mainly associated with vegetated habitat types (seagrass, algal beds), while Xyrichtys martinicensis and Coryphopterus glaucofraenum were common over unvegetated sandy habitat types. Cluster analysis among backreef lagoon habitat types based on the entire fish density data showed distinct associations of fish assemblages by habitat type, regardless of season. Fish assemblages in the more structured habitat types were similar to each other but different from unstructured vegetated, and unvegetated habitat types. These results suggest that differences in fish species richness and density in the backreef lagoon are related to habitat type. The ecological importance and need for protection of backreef lagoon habitat types are discussed in relation to their potential role as nurseries for many fish species.

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