The influence of bottom type and shelf position on biodiversity of tropical fish inside a recently enlarged marine reserve

Abstract

Abstract A necessary component of implementing a successful marine reserve is the quantification of the biological resources that fall under its protection. Without such an initial assessment, the future effects of the reserve on the local habitat and biotic community cannot be quantified and will remain the subject of debate. This study provides such a baseline assessment of fish diversity and habitat types within a recently enlarged marine reserve. Buck Island Reef National Monument, US Virgin Islands, was recently enlarged from approximately 4 km2 to over 76 km2. Areas of sand, seagrass, and hard‐bottom under protection were increased from 0.29 km2, 0.47 km2, and 1.96 km2 to 2.70 km2, 2.89 km2, and 18.30 km2 respectively when the Monument was expanded. A 53 km2 area of pelagic/deep‐water habitat with unknown bottom type is now also protected by the Monument. Visual counts of fish within 25×4 m2 transects conducted during the day were used to assess fish community structure and habitat utilization patterns. Species richness, diversity, assemblage structure, and fish density were evaluated and compared among sand, seagrass, and hard‐bottom habitats. Hard‐bottom sites had over twice the mean species richness and diversity as sand and seagrass sites, and several times greater mean fish density. Quantification of the fish community in pelagic and deep‐water habitats within the reserve is recommended to provide a more comprehensive assessment of the offshore areas of the reserve. Fish numbers, size, and diversity outside the reserve boundaries must also be evaluated to allow quantification of the effects of the marine reserve on the adjacent fish communities. Copyright © 2004 John Wiley & Sons, Ltd.