13C and δ 15 N stable isotope values occurred over spatial scales of hundreds of meters. Some of this variation is consistent with the spatial mosaics of seagrass, sand flat and mangrove habitats available to fish. In a nearly pristine system, fish captured in mangrove systems show fine scale variability in stable isotope values, but we found no indication that mangrove productivity directly supported local fish populations through the trophic web.

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages. Shark-dominated assemblages persist in wealthy nations with strong governance and in highly protected areas, whereas poverty, weak governance, and a lack of shark management are associated with depauperate assemblages mainly composed of rays. Without action to address these diversity deficits, loss of ecological function and ecosystem services will increasingly affect human communities.