This article was written by the University of Hawaiʻi.
A new study published in Current Biology by oceanographers from the University of Hawai’i at Mānoa, revealed habitats of thirty species of sharks, rays, and chimaeras (also known as ghost sharks) overlap with areas targeted for deep-sea mining.
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), said nearly two-thirds of these species are already at risk of extinction from human activities.
Deep-sea mining, which disturbs the seafloor and sends massive plumes of sediment into surrounding waters, could make their situation even worse by further damaging fragile ecosystems.
“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.”
Judah continued to say “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.”
Judah and an international team of experts, overlayed global maps of species ranges created by the International Union for Conservation of Nature (IUCN) Shark Specialist Group with contract and reserved areas allocated for deep-sea mining by the International Seabed Authority.
The researchers also accounted for how each species reproduces and how deep they dive in order to estimate their vulnerability to mining impacts.
For example, species such as skates and chimaeras lay eggs on the seafloor and therefore mining vehicles could pose a threat to nurseries.
The species they assessed included iconic examples such as the whale shark, manta rays and the megamouth shark, and also many lesser known species, such as the pygmy shark, chocolate skate and small-eyed rabbit fish, which comes from a unique group of cartilaginous fishes similar to sharks and rays, sometimes called ghost sharks.
The team discovered that 30 species could be impacted by discharge plumes and 25 of the 30 species could also be impacted by seafloor disruptions associated with mining. They also found that because many of the species inhabit a variety of habitats along the depth range or are deep divers, mining impacts may overlap more than half of the depth range of 17 species.
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 Hawaiʻi into the eastern Pacific Ocean.
Jeff Drazen, study senior author and professor of oceanography at SOEST, said “sharks and their relatives are the second most threatened vertebrate group on the planet, mostly from overfishing. 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.”
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.
Picture: Pygmy Shark, the world’s second smallest shark species. (Photo credit: Blue Planet Archive / Masa Ushioda).