April 27, 2026 — A sweeping three-decade study has confirmed that conservation measures in the western Atlantic have turned U.S. and Canadian waters into a critical refuge for Atlantic bluefin tuna — including fish that originate in the heavily fished eastern Atlantic and Mediterranean.
The findings, published in the Proceedings of the National Academy of Sciences, are based on electronic tagging data from 1,720 bluefin tuna tagged between 1996 and 2025, combined with catch records going back to 1950. The international research team was led by Dr. Barbara Block of Stanford University and included scientists from NOAA Fisheries, Acadia University, the University of Hawaiʻi, the Swedish University of Agricultural Sciences, the Institute of Marine Research in Norway, the Marine Institute in Ireland, and the Barcelona Zoo Foundation in Spain.
A TALE OF TWO FISHERIES
The catch data paint a stark picture of unequal fishing pressure across the Atlantic. Of total bluefin landings since 1950, the Mediterranean Sea alone accounted for 55 percent, while the entire western Atlantic—all waters west of the 45°W management line—accounted for just 11 percent. That disparity has widened in recent decades: the Mediterranean now represents 72 percent of Atlantic-wide bluefin catches.
Fishing pressure in the Mediterranean intensified sharply through the 1990s and 2000s, driven in part by the rise of capture-based aquaculture targeting more mature fish. Catches peaked at 60,000 metric tons in 2007—nearly double the scientific recommendations at the time. Historically, Mediterranean purse seine fisheries targeted juvenile fish aged one and two, removing them before they could grow large enough to migrate into the open Atlantic. In 2010, following widespread concern about the stock’s status, the International Commission for the Conservation of Atlantic Tunas (ICCAT) implemented significant quota cuts and binding conservation measures.
The western Atlantic has operated under a very different management regime. For more than 45 years, western catches have adhered to binding total allowable catch limits — typically a tenth of the eastern quota — and have included strong conservation measures such as prohibitions on targeted fishing in the Gulf of Mexico, renamed by the Trump administration as the Gulf of America.