From gentle giants to ghostly hunters, sharks face an unseen peril

"Deep-sea mining is a new potential threat to this group of animals which are both vital in the ocean ecosystem and to human culture and identity," said Aaron Judah, lead author of the study and an oceanography graduate student at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). "By identifying and calling attention to this threat and recommending potential conservation pathways, I hope we will be better positioned to support healthy shark, ray, and chimaera populations into the future."

Mapping Shark Hotspots and Mining Zones

To assess the scale of the risk, Judah and an international research team compared maps of species ranges from the IUCN Shark Specialist Group with mining contract areas designated by the International Seabed Authority. The scientists also analyzed how each species reproduces and how deep they live to estimate how exposed they are to mining activity. For example, skates and chimaeras lay eggs directly on the seafloor, meaning that mining vehicles could destroy their nursery areas.

The assessment included both well-known species such as whale sharks, manta rays, and the rarely seen megamouth shark, along with lesser-known deep-sea species including the pygmy shark, chocolate skate, and point-nosed chimaera. Chimaeras belong to a unique group of cartilaginous fishes related to sharks and rays and are often called ghost sharks because of their pale, spectral appearance.

The researchers determined that thirty species could be affected by the sediment plumes released by mining operations, and twenty-five of them could also face habitat disruption from direct contact with mining machinery on the seafloor. Many of these species live across a wide range of ocean depths or make deep dives, meaning that mining could interfere with more than half of their natural depth range in at least seventeen cases.

Assessing Impacts to Protect Ocean Life

Deep-sea mining is set to potentially occur in the Clarion-Clipperton Zone, which is a large abyssal plain area that spans from the waters around Hawai'i into the eastern Pacific Ocean. To make the best management decisions, the potential impacts on marine life and the communities that depend on them must be known.

"Sharks and their relatives are the second most threatened vertebrate group on the planet, mostly from overfishing," said Jeff Drazen, study senior author and professor of Oceanography at SOEST. "Because of their vulnerability, they should be considered in ongoing discussions of the environmental risks from deep-sea mining, and those responsible for monitoring their health should be aware that mining could pose an additional risk."

Recommendations for Shark Conservation

The authors offer a number of recommendations to improve conservation of these species under the footprint of mining, such as establishing monitoring programs, including them in environmental impact assessments, and creating protected areas. These recommendations could be adopted by the International Seabed Authority in their regulations for creating environmental impact assessments, or by contractors in executing scientific baseline assessments.

"Many of the shark species identified in the analysis are highly mobile and can move across wide swaths of ocean," said Judah. "Given their mobility and the proximity of Hawai'i to the areas allocated for mining, impacts in these areas may stretch indirectly to ecosystems near the island chain."

Judah continues to research and report species range extensions for animals not included in the initial assessment, which may add additional species to this group of animals at risk from mining impacts.