- A new study indicates that deep-sea mining could threaten at least 30 species of sharks, rays and chimaeras, many of which are already at risk of extinction.
- The authors found that seabed sediment plumes and midwater discharges of wastewater from mining activities could cause a range of impacts on shark, ray and chimaera species, including, but not limited to, disruptions to breeding and foraging, alterations in vertical migration, and exposure to metal contamination.
- The authors recommend precautionary measures, including improved baseline monitoring, the development of protected zones, and discharging wastewater below below 2,000 m (about 6,600 ft).
- With companies planning to begin deep-sea mining in international waters as early as 2027, the authors say more research is urgently needed to understand the full ecological impact of this emerging industry on biodiversity.
New research has found that deep-sea mining in international waters could threaten at least 30 species of sharks, rays and chimaeras — many of which are already at risk of extinction.
Chondrichthyes, the class of cartilaginous fish that includes sharks, rays and chimaeras, are among the most threatened vertebrates on Earth, with more than 37% of species at risk of extinction due to overfishing and habitat loss, the study notes. Now, scientists warn that these animals could face new threats if deep-sea mining kicks off in international waters.
While commercial deep-sea mining has not yet started, some companies are looking to launch operations in the near future. Yet significant uncertainties remain about the environmental impacts of this proposed industry, in which miners would send heavy machinery into the deep ocean to collect valuable minerals, such as manganese, cobalt, copper and nickel.
“Many animals haven’t been accounted for in the potential impacts of deep-sea mining,” Aaron Judah, lead author of the new study and a doctoral student at the University of Hawai‘i at Mānoa, told Mongabay. “There has been work on migrating fishes in the water column, invertebrates on the seafloor, and microbes — but a lot of the top predators have been left out of a lot of the discussions. There’s been recent work done in whales, but sharks and rays were just mostly not included whatsoever.”
How could deep-sea mining impact Chondrichthyans?
The study, published in Current Biology on Oct. 2, overlays global maps of species ranges, created by the IUCN Shark Specialist Group, with areas allocated for deep-sea mining in international waters by the International Seabed Authority (ISA), the U.N.-mandated mining regulator. The ISA mining areas are in the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean, the Western Pacific Ocean, and the Central Indian Ocean Basin.
This process allowed the authors to identify 30 shark, ray and chimaera species in areas earmarked for mining. These species include whale sharks (Rhincodon typus), mako sharks (genus Isurus), manta rays (genus Mobula) and deep-sea dwellers such as chocolate skates (Rajella bigelowi), megamouth sharks (Megachasma pelagios) and small-eyed rabbitfish (Hydrolagus affinis). The IUCN, the global conservation authority, classifies 10 of these species as endangered or critically endangered, eight as vulnerable to extinction, and three as near threatened.
The authors accounted for how each species reproduces and how deeply they dive in order to assess how deep-sea mining might affect them. They also assessed all three kinds of deep-sea mining: Mining for polymetallic nodules on the seafloor’s abyssal plains; mining for polymetallic sulfides near hydrothermal vents; and mining for cobalt-rich ferromanganese crusts on seamounts.
They determined two main pathways for potential impact on chondrichthyans. One is benthic sediment plumes raised by collector vehicles extracting minerals from the seafloor, which the study notes could disrupt nurseries and foraging grounds. The other is discharges of wastewater laden with sediment and metals into the water column, which could potentially harm organisms in various ways, such as reducing visibility, altering foraging habits, introducing toxic metals into the water, and causing respiratory distress. The study notes that filter feeders and light-sensitive species might be particularly vulnerable to these kinds of stressors.
Judah said metal toxicity could ultimately affect seafood consumed by people. For example, he said, the blue shark (Prionace glauca), whose range the study found overlapped with all three types of mining areas, is one of the main species sold internationally for shark meat. “What does that mean for metal accumulation in a very real and large global trade?” Judah asked.
Luke Warwick, director of shark and ray conservation at U.S.-based NGO the Wildlife Conservation Society, who wasn’t involved in the study, agreed that deep-sea mining introduced the risk of metal accumulation and metal toxicity in species that are already known to bioaccumulate metals at high levels. However, he noted that the biggest threat to many shark, ray and chimaera species is still overfishing. This, he said, could wipe certain pelagic species out before deep-sea mining even begins on a commercial level. For Warwick, the bigger concern is for benthic species, which are slower growing. “Because of their habitat use, [deep-sea mining] could be almost as great as deliberate killing of them through fishing,” Warwick told Mongabay.
‘The ocean is highly connected’
The study indicates that sulfide and crust mining would likely pose the most significant and direct risks to sharks, rays and chimaeras, mainly because of the substantial overlap between these species and the mining areas. For instance, 26 of the 30 species identified in the study inhabit zones proposed for sulfide mining, and some of them lay their eggs around vent systems, where sulfide mineral deposits occur. Species potentially impacted by sulfide mining included chocolate skates, Portuguese dogfish (Centroscymnus coelolepis), great lantern sharks (Etmopterus princeps) and small-eyed rabbitfish. Cobalt-rich ferromanganese crust mining could impact 21 of the identified species, the study showed, including whale sharks, cookiecutter sharks (Isistius brasiliensis) and sicklefin devil rays (Mobula tarapacana).
When it comes to polymetallic nodule mining, the form of deep-sea mining likely to begin soonest, the study found that 20 species overlap with potential mining zones. Nodules occur on abyssal plains 4,000 to 6,000 meters (about 13,100 to 19,700 feet) below the surface, but the study found no species living at these depths in the nodule-mining areas, so anticipated mining disturbances at these depths would pose little risk to chondrichthyans. (Other research indicates that seafloor nodule mining would affect numerous other species, such as deep-sea corals, sponges and sea anemones.) Nodule mining would, however, likely generate midwater plumes of sediment-laden wastewater that could threaten deep-diving species, such as whale sharks, cookiecutter sharks and sicklefin devil rays, which descend to depths of 1,500 m (about 4,900 ft) or deeper.
To reduce potential impacts, the authors recommend discharging plumes below 2,000 m (about 6,600 ft), or even directly at the seafloor. Still, they caution that these midwater plumes are likely to expand considerably over many square kilometers, regardless of their depth, with largely unknown impacts on midwater communities. Moreover, the cumulative effect of releasing such plumes throughout a mine’s decades-long lifespan remains uncertain.
“The ocean is highly connected, so there will probably still be impacts on these animals,” Judah said.
Jeff Drazen, study co-author and an ecologist at the University of Hawai‘i at Mānoa, told Mongabay that many animals, including prey species like small fishes, squids and shrimps, move vertically in the water column.
“They could become contaminated, move to another depth in the water column and bring that contamination with them,” Drazen said. “The extent to which such things happen, we do not know, because the deep mid-waters are the most poorly studied ecosystem on the planet.”
Drazen explained the logic of discharging wastewater on the seabed rather than in the water column, as the paper suggests. “If a company is going to make a mess, if you will, on the seafloor with their mining activity, then why make a mess in a second place?” he said. “It’s sort of a prime tenet of conservation that you minimize the scale of impacts by minimizing their footprint.”
Canada-based The Metals Company (TMC) has stated that it intends to discharge wastewater at 2,000 m from its planned polymetallic nodule mining, and in an Oct. 8 LinkedIn post, it appeared to frame the Current Biology paper as supporting this approach. “While the paper leads with dire warnings about potential impacts on pelagic species higher up in the water column — depths where virtually no deep-sea mining contractors plan to release return water — it quietly buries the real headline: 0% overlap at 2,000 meters for sharks and other key species studied,” the company said in the post. “In other words, the selected midwater return depth works exactly as intended.”
TMC did not respond to Mongabay’s questions about the study’s suggestion to discharge below, rather than right at, 2,000 m, or whether the company would adjust its mining plans based on these findings. Neither did it answer questions about whether it had studied the impacts of its proposed operations on sharks, rays and chimaeras.
‘A lot more work to do’
Judah pointed out that while the research drew from the most complete data available from the IUCN, much of the deep sea remains unexplored, so the study’s findings likely underrepresent the risks chondrichthyan species face.
“I’m sure that the list we’ve compiled is the baseline underestimate,” he said. “I think there are a lot more species that we just have not sampled yet.”
The paper concludes with a set of recommendations. In addition to discharging wastewater below 2,000 m, it proposes that international organizations and conservation bodies, such as the ISA and IUCN, regularly update evaluations of deep-sea mining threats to chondrichthyans. It calls for improved baseline monitoring using methods like baited and pelagic cameras, tagging studies and egg case surveys. And it suggests developing spatial management tools to protect vulnerable habitats.
With mining for polymetallic nodules on the horizon, Judah emphasized the need for more research to fully understand the effects on sharks, rays and chimeras.
“There is a lot more work to do in these nodule areas,” he said. “Further exploration and further data collection may reveal something new.”
Elizabeth Claire Alberts is a senior staff writer for Mongabay and was recently a fellow with the Pulitzer Center’s Ocean Reporting Network. Find her on Bluesky and LinkedIn.
Banner image: A manta ray in the Indian Ocean. Image by Anett Szaszi / Ocean Image Bank.
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Citations:
Judah, A. B., Mull, C. G., Dulvy, N. K., Finucci, B., Assad, V. E., & Drazen, J. C. (2025). Deep-sea mining risks for sharks, rays, and chimaeras. Current Biology. doi:10.1016/j.cub.2025.09.019
Hauser-Davis, R. A., Wosnick, N., Chaves, A. P., Giareta, E. P., Leite, R. D., & Torres-Florez, J. P. (2024). The global issue of metal contamination in sharks, rays and skates and associated human health risks. Ecotoxicology and Environmental Safety, 288, 117358. doi: 10.1016/j.ecoenv.2024.117358
Jones, D. O., Arias, M. B., Van Audenhaege, L., Blackbird, S., Boolukos, C., Bribiesca-Contreras, G., … Glover, A. G. (2025). Long-term impact and biological recovery in a deep-sea mining track. Nature, 642(8066), 112-118. doi:10.1038/s41586-025-08921-3
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