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Coral reef fish communities, diversity, and their fisheries and biodiversity status in East Africa

Timothy R. McClanahan

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ABSTRACT: Coral reef fish along the East African coast were evaluated for having distinct communities, their distributions, and interactions with the environment and management. I studied the biomass and species richness of 24 fish families in 238 unique sites in Kenya, Tanzania, and Mozambique. I identified an unfished benchmark that was associated with high biomass, high compliance closures, or low access to fishing and 6 additional statistically different communities. In the benchmark community, biomass was dominated by snappers, surgeonfish, parrotfish, and wrasses. Eleven of the 24 families studied declined relative to the benchmark community with the greatest declines observed among surgeonfish, snappers, sweetlips (grunts), groupers, and triggerfish. I evaluated the community’s spatial distributions and associations of 15 of 23 environmental and human-impact variables that were selected. Fish biomass was most positively influenced by the extent of shallow water <50 m adjacent the sites, depth, and high compliance closures and negatively by human populations within a 100-km radius of the site. Number of fish species was largely predicted by biomass with weak evidence for local environmental control. Classification of the biomass into 3 proposed management thresholds found that ~38% of the sites were below sustainable yields, 54% below maximum species richness, and 92% below a proposed stable-ecosystem or conservation threshold. Therefore, increasing biomass of vulnerable taxa through fishing restrictions is recommended for maintaining sustainable fisheries, species diversity, and ecosystem services.