Climate change is rapidly altering the world’s oceans, forcing many commercially important fish species to shift their natural ranges. According to a new study published in Science Advances, more than half of the world’s straddling fish stocks—species that migrate between national waters and international high seas—will cross maritime borders by 2050.
Most of these shifts will move stocks into the high seas, an area where fisheries management is weak, leaving species more vulnerable to overfishing.
What Are Straddling Fish Stocks?
Straddling stocks are species whose populations overlap between exclusive economic zones (EEZs)—waters up to 200 nautical miles from a country’s coast—and the open ocean. Examples include:
- Silky sharks (Carcharhinus falciformis)
- Blue sharks (Prionace glauca)
- Skipjack tuna (Katsuwonus pelamis)
- Yellowfin tuna (Thunnus albacares)
These species are vital for global food security and economies, especially in developing countries that depend heavily on fisheries revenue.
Why Climate Change Is Driving the Shift
Rising sea temperatures, changing salinity levels, and declining oxygen are forcing fish to seek new habitats. The study used advanced modeling systems to project these shifts and found:
- One-third of identified stocks will move into the high seas by 2050.
- One-fifth will shift into EEZs, but mostly in temperate rather than tropical waters.
- Both low-emission and high-emission scenarios showed similar patterns up to 2050.
As marine species move, tropical countries—least responsible for climate change—are at risk of losing access to critical fisheries resources.
Consequences for Tropical Nations
For many small island developing states (SIDS), tuna fisheries represent a financial lifeline. Nations like Kiribati, Solomon Islands, and Papua New Guinea collectively sell access rights to tuna fishing in their EEZs, generating essential revenue.
However, the study predicts that 58% of straddling stocks in the central Indo-Pacific region will move into the high seas, leaving tropical nations at a disadvantage. Without strong governance, they may lose both food security and economic stability.
Calls for Better Fisheries Governance
Experts argue that climate-driven shifts demand stronger international cooperation. Currently, Regional Fisheries Management Organizations (RFMOs) such as the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC) are responsible for tuna stocks, but critics say these organizations are slow to adapt to climate challenges.
Some researchers, including co-author Rashid Sumaila, even call for a ban on high seas fishing, suggesting that it could protect biodiversity and prevent wealthy nations from monopolizing displaced fish stocks.
The Urgent Need for Climate-Resilient Fisheries
The study highlights two critical issues:
- Equity and justice – Tropical nations risk losing fisheries resources despite contributing little to climate change.
- Sustainability – The high seas are poorly regulated, increasing the risk of overexploitation.
Experts stress that nations and international bodies must adopt climate-informed fisheries management, including:
- Improved data collection and stock monitoring
- Stronger collaboration between RFMOs
- Localized studies to understand regional shifts
As lead author Juliano Palacios-Abrantes notes, “Climate change is sending a whole bunch of fisheries out into the lion’s den.”
Final Thoughts
The redistribution of fish stocks due to climate change poses serious ecological, economic, and social challenges. Without urgent action, tropical nations stand to lose critical resources while the high seas become a hotspot for overfishing.
This study serves as a wake-up call for policymakers, fisheries managers, and conservationists to ensure that future ocean governance is fair, sustainable, and climate-resilient.
Source: Palacios-Abrantes et al. (2025), Science Advances – DOI: 10.1126/sciadv.adq5976