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

Abstract

Coral reef fish along the East African coast were evaluated for the distinctiveness of their communities, their distributions and interactions with the environment, and their responses to management. I studied the biomass and species richness of 24 fish families at 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 along with 6 additional statistically different communities. In the benchmark community, biomass was dominated by snappers, surgeonfish, parrotfish, and wrasses. Of the 24 families studied, 11 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. Fish biomass was most positively influenced by the extent of shallow water <50 m adjacent to the sites, depth, and high-compliance closures and negatively impacted 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 revealed that ~38% of the sites were below sustainable yields, 54% were 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.