Coral reef sites around the world where fish biomass levels are substantially higher or lower than expected are identified in a study published in Nature. The findings stem from a previously unexplored, interdisciplinary approach - taking into account environmental and socioeconomic factors - which may help tackle the global decline among the world’s coral reefs.

Joshua Cinner and colleagues compile data from 2,514 coral reefs worldwide, and develop a model to quantify how reef fish biomass is related to environmental variables, such as depth, habitat and productivity, and to socioeconomic drivers, including markets, affluence, governance and population. In the model, the metric that measures interaction with urban centres has the strongest relationship with reef fish biomass. They also identify 15 so-called ‘bright spots’ and 35 ‘dark spots’ among the world’s coral reefs, defined as sites with biomass levels that significantly deviate (by more than two standard deviations) from expectations inherent in their model. Surprisingly, bright spots included populated localities, where use of ecosystem resources is high, and conversely, some remote places such as part of the northwestern Hawaiian Islands were identified as dark spots.

Following surveys of local experts at these sites, the authors find that bright spots are characterized by strong sociocultural institutions and high levels of local engagement in management, high dependence on marine resources, and good environmental conditions, such as deep-water refuges. Conversely, dark spots are distinguished by technologies that allow for more intensive fishing, as well as a recent history of environmental shocks (such as cyclones).

These results suggest that strengthening fisheries governance may facilitate coral reef conservation in the future.