IUCN adopts Motion 035 to safeguard the ocean twilight zone, urging a global precautionary pause on mesopelagic fishing and deep-sea exploitation
The International Union for the Conservation of Nature (IUCN) has adopted a major new global motion calling for the protection of the ocean’s mesopelagic zone, commonly known as the “twilight zone”, a vast, deep-water ecosystem vital for climate regulation, biodiversity, and the global food chain.
Motion 035, titled Protection of Mesopelagic Ecosystem Integrity, was passed at the IUCN World Conservation Congress in Abu Dhabi. The measure, championed by the US-based Ocean Conservancy, urges a precautionary pause on any new mesopelagic fishing or industrial activity until sufficient scientific understanding and legal safeguards are in place.
Chris Dorsett, Vice President of Conservation at Ocean Conservancy, said: “Today is a big day for small fish – species that live in the twilight zone don’t make it onto restaurant menus, but they form the base of the ocean food chain and carry important climate regulation functions. By passing IUCN Motion 35, and urging a precautionary approach, the world is sending a strong message that the ocean twilight zone is vital to life on Earth, and must be protected.”
Safeguarding an Unseen but Essential Ecosystem
According to the IUCN resolution, the mesopelagic zone lies between 200 and 1,000 metres below the ocean surface and may contain up to 95% of the planet’s total fish biomass. It is home to countless species that migrate vertically through the water column each day, transporting and sequestering between 2 and 6 gigatonnes of carbon annually — more than twice the carbon produced by all the world’s cars.
The newly adopted motion emphasises the zone’s vital role in global climate regulation and food webs but warns that growing industrial interest in deep-sea fishing, carbon removal technologies, and seabed mining poses serious threats to its ecological integrity.
A Call for a Global Precautionary Pause
The motion urges IUCN members and governments to impose a “precautionary pause” on any new or expanded mesopelagic fisheries or industrial activities unless key scientific and regulatory conditions are met — including clear understanding of the ecosystem’s structure and function, transparent catch reporting, and assurances that no adverse impacts will occur.
It also calls on the international community to recognise the role of mesopelagic species in climate regulation and to use management measures such as marine protected areas to safeguard these deep-sea ecosystems.
Legal and Policy Context
The IUCN’s call references international frameworks such as the UN Convention on the Law of the Sea (UNCLOS), the UN Fish Stocks Agreement, and the Port State Measures Agreement, as well as the new Agreement on Biodiversity Beyond National Jurisdiction (BBNJ). It links the motion to multiple UN Sustainable Development Goals, including climate action and life below water.
What is the IUCN?
The International Union for the Conservation of Nature (IUCN) is the world’s largest and most influential environmental network, comprising over 1,400 member organisations including governments, NGOs, and scientific institutions. It provides the global standard for conservation policy, including the IUCN Red List of Threatened Species, and convenes its World Conservation Congress every four years to set international conservation priorities.
Ocean Conservancy Applauds Decision
The Ocean Conservancy described the vote as a landmark step in ocean protection. The organisation, which has worked for over 50 years to unite science, policy, and advocacy for marine conservation, said the IUCN motion reflects a growing global awareness of the importance of deep-sea ecosystems for both biodiversity and climate stability.
