Fishing for oil and meat drives deepwater shark and ray decline

The international liver oil and meat trade is driving rapid depletion of deepwater sharks and rays – an outcome that is potentially irreversible due to these animals’ extremely slow life histories. The findings highlight the need for immediate trade and fishing regulations . The deep ocean – the largest and one of the most complex ecosystems on Earth – is considered the last natural biodiversity refuge from the reach of human activities. It also remains one of the Earth’s least-studied environments. As such, there have been no comprehensive evaluations of the state of deepwater biodiversity. Despite international commitments to conserve 30% of the world’s oceans, no policy-relevant indicators exist to guide global conservation target setting or tracking. To address this need, Brittany Finucci and colleagues calculated global biodiversity change indicators of, status of, and threats to deepwater sharks and rays. Using the most comprehensive assessment of this group, encompassing all 521 species of deepwater sharks and rays, Finucci et al. estimated the species’ sensitivity compared to other exploited marine vertebrates, analyzed trends in their relative abundance, and evaluated their global extinction risk and the underlying patterns of use and trade. They found that deepwater sharks and rays are among the most sensitive marine vertebrates to overexploitation. According to the authors’ findings, one-third of threatened deepwater sharks are targeted for fishing and half of the species targeted for the international liver-oil trade are threatened with extinction. This activity is driving a steep population decline, which, given the species’ characteristic slow life histories, long life spans, and very low reproductive output, cannot be easily reversed. Moreover, many of these species are not protected by current management strategies. Finucci et al. demonstrate that a worldwide depth limit to fishing activity and an expansion of no-fishing areas could enhance protection for many of these species if implemented alongside international fishing and trade regulations. 

For reporters interested in trends, a November 6 report in Science by Worm et al. found that sharks continue to be overexploited by fisheries despite widespread regulations aimed at reducing wasteful shark-finning activities.