生態学：サンゴ礁のカメラが捉えたサメの存在

Fishing has had a substantial impact on global reef shark populations according to a global survey of coral reef sharks published online in Nature. Data from more than 15,000 underwater video stations reveal that sharks were absent from nearly one fifth of reefs surveyed. These findings could potentially guide policies to restore and manage reef shark populations.

Aaron MacNeil and colleagues conducted a global survey to quantify the status of reef sharks, using data from 15,165 underwater video stations deployed on 371 reefs in 58 countries, states and territories over a three-year period. The authors found that 63% of the video stations did not record a shark and no sharks at all were observed at 69 out of 371 (19%) reefs. The findings indicate that there has been widespread depletion of reef sharks across much of the world’s tropical oceans.

The authors also investigated how a range of management practices could affect the abundance of reef sharks. They found that the presence of a shark sanctuary (where no targeted catch or trade in shark products is allowed) was associated with 50% higher relative abundance compared to nations without sanctuary status. In places in which sharks are fished and regulations are currently absent, the authors estimate that introducing catch limits may increase regional abundance by 15% on average, while banning certain equipment and introducing closed areas may increase abundance by 9% and 8% on average, respectively.

The results suggest that concern over the global status of reef sharks is warranted, especially in the Western Pacific, Indian Ocean and Western Atlantic regions. Opportunities for conservation remain, but the most appropriate direct management strategies for conservation depend on the nature of local fisheries, social norms and cultures, as well as some understanding of relative shark abundance, according to the authors.