Coral Reef Sharks Driven Toward Extinction by Overfishing

Five of the most common shark species living in coral reefs have declined 60% to 73%, according to a massive global study by Colin Simpfendorfer and colleagues. Some individual shark species were not found at 34% to 47% of the reefs in the survey. The likely cause, say the authors, is overfishing, which has removed both the sharks themselves and the prey they depend on. As shark numbers decline, ray species are increasing on the reefs, suggesting a shift in the top elasmobranch species in the communities. Simpfendorfer et al. surveyed 391 coral reefs in 67 nations and territories using 22,756 remote underwater video stations. They show that shark-dominated reefs persist in wealthy, well-governed nations and in protected marine sanctuaries. In areas of poverty and limited governance, rays dominate the reef communities. The estimated declines of these resident reef shark species meet the IUCN Red List criteria for Endangered status, the researchers note. In a related Perspective, David Shiffman discusses how the authors, under the Global FinPrint project, analyzed almost three years' worth of raw video. The study is "the latest in a long line of papers showing that global-scale problems require huge and multidisciplinary teams," Shiffman writes.