Risks of conflict between fishing and ocean carbon sequestration

[Press Release] - Published on March 26, 2025 in Press Room, Science and Society

An An international team led by researchers from the University of Montpellier, the CNRS, and the University of California has mapped areas of potential conflict between two major contributions of the ocean to human societies: fishing and carbon sequestration. With just a few months to go before the opening of the^3rd United Nations Ocean Conference, to be held in Nice in June 2025, their work, published in the journal One Earth, offers innovative approaches to adapting fishing practices.

Fishing and Carbon Sequestration in the Ocean: A Long-Neglected Link

On land, the impact of agriculture on forests as carbon sinks is now well understood. In contrast, the link between fishing and carbon sequestration by the oceans remains less well understood. Through their carcasses and the carbon-rich waste they produce—which sinks into the deep sea—fish play a direct role in carbon sequestration in the deep ocean. Ocean sediments, meanwhile, store vast quantities of carbon accumulated over time in the sediment, known as blue carbon. The problem is that fishing, by removing large quantities of fish and damaging the seafloor through techniques such as bottom trawling (a method involving the use of a trawl net that comes into direct contact with marine sediment), drastically limits the oceans’ ability to sequester this blue carbon.  

While the conflict between blue carbon and the socioeconomic benefits of fishing (jobs, food security, etc.) has been highlighted for several years, the extent and location of these potentially conflicting areas were previously unknown. This new study reveals that these areas cover 15% of the ocean, spanning both international waters and coastal regions.

Fish play a crucial role in the ocean carbon cycle, directly contributing to carbon sequestration in the deep ocean through the regular production of carbon-rich fecal pellets and carcasses that sink into the abyss, thereby trapping the carbon they contain for several centuries. © IRD – Ifremer

International waters, a major flashpoint

International waters, which are not under the direct authority of any state and where deep-sea fishing takes place, account for nearly 50% of the conflict zones identified in this study.  “However, other studies have shown that deep-sea fishing is recognized as contributing very little to global food security because it is primarily conducted by developed countries that do not face food insecurity issues,” the study’s authors note. “Our study therefore provides further justification for applying the precautionary principle—that is, limiting deep-sea fishing until its impacts on carbon sequestration are assessed,” they conclude.

Benthic trawling and carbon sequestration: a coastal conflict

While protecting the high seas will have little impact on global socioeconomic goals such as food security, the situation is quite different when it comes to bottom trawling in coastal waters. Indeed, although the areas where carbon sequestration in sediment and bottom trawling conflict cover only 3.8% of the ocean, more than 56% of bottom trawl catches occur there. “This shows that significant conflicts can arise if these areas are protected from trawl fishing. These conflicts are all the more significant when the identified areas involve countries facing food insecurity,” the researchers note.

Solutions are available

The study shows, however, that solutions do exist. “Let’s take a simple example. The Argentine coast is identified as a conflict area because it is of critical importance for carbon sequestration in the sediment, but also for trawl fishing. However, certain species can also be caught using gear that does not come into contact with the sediment. This is the case, for example, with Argentine hake, which is typically caught using bottom trawls that contact the sediment, but can also be caught with pelagic trawls or by line fishing. “Thus, changing fishing methods would make it possible to maintain the jobs and socio-economic benefits derived from Argentine hake fishing, while preserving the carbon stock present in the sediment,” the study’s authors explain.