One in seven deep sea sharks and rays faces extinction risk

Credit: Greg Amptman

Deepwater sharks and rays, mysterious creatures that dwell in the ocean’s shadows, are facing a dire threat due to overfishing, reveals an extensive eight-year study published in the journal Science.

This comprehensive research, involving over 300 experts worldwide, has sounded an alarm for the survival of these enigmatic beings that prefer the ocean’s depths, far beyond the reach of sunlight.

Sharks and rays, particularly those that inhabit waters deeper than 200 meters, are being inadvertently caught in vast numbers by fisheries aimed at more lucrative catches.

Yet, due to the value of their oil and meat, these deep-sea dwellers are not released but kept, contributing to a worrying decline in their populations. This decline is further exacerbated by the booming global trade in shark liver oil, an ingredient cherished in various industries, from cosmetics to medicine.

Nicholas Dulvy, a leading figure in marine biodiversity and conservation, points out the grave irony that many of these deepwater species only encounter sunlight when they’re tragically brought onto the decks of fishing vessels.

His research has identified approximately 60 species of sharks and rays now facing a high risk of extinction, according to the stringent criteria set by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

The heart of the problem lies in the technological advancements that have enabled fishing operations to extend their reach to previously untouched oceanic depths, up to a kilometer deep.

This expansion into the deep sea targets creatures that are especially vulnerable due to their long lifespans and slow reproductive cycles. Sharks and rays share more in common with marine mammals like whales and walruses, known for their longevity and low birth rates, than with other fish.

Some species, such as the Greenland Shark, may take decades to reach maturity and have exceedingly sparse offspring, making them particularly susceptible to overfishing.

The value placed on shark liver oil, used in products ranging from beauty creams to health supplements, and even vaccines, has driven this exploitation.

Similarly, the demand for fermented skate, a traditional Korean dish, has led to increased targeting of these species. While efforts have been made to regulate the trade of shark fins, Dulvy emphasizes the urgent need to also manage the trade in liver oil to prevent these deep-sea species from edging closer to extinction.

The study advocates for bold conservation measures, including the ambitious goal of protecting 30% of the world’s oceans by 2030. Specifically, safeguarding a portion of the deep ocean (200 to 2,000 meters) could offer significant protection to 80% of species, according to the research.

Furthermore, a global ban on fishing below 800 meters might create a refuge for a third of the threatened deepwater sharks and rays, providing them a chance to recover and thrive.

This call to action is part of the Global Shark Trends Project, a collaboration among Simon Fraser University, the IUCN Shark Specialist Group, James Cook University, and the Georgia Aquarium.

Their work shines a light on the hidden crisis unfolding in the depths of our oceans, urging immediate action to safeguard these ancient mariners of the deep.

The research findings can be found in Science.

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