November 15, 2023 — In November 1981, a fleet of briefcase-toting lobbyists, scientists, and political negotiators gathered in sunny Tenerife, Spain, to decide the fate of Atlantic bluefin tuna. Representing more than a dozen countries, including Canada, the United States, Spain, and Italy, the besuited men knew crisis loomed. Since the early 1970s, rising global demand for bluefin flesh had spurred fishing fleets—hailing from ports on both sides of the Atlantic Ocean—to kill untold thousands of the wide-ranging predator every year. Under this heavy fishing pressure, primarily driven by the Japanese appetite for sushi-grade tuna, the species careened toward collapse.
During the meeting in Tenerife, the American delegation to the International Commission for the Conservation of Atlantic Tunas proposed a disarmingly simple solution: they would draw a line down the middle of the Atlantic Ocean and split the bluefin into two separate stocks. The Europeans could only fish east of the line, while the Canadians, Americans, and Japanese would fish west of it, limiting their catches to let the population recover.
The proposal passed and, eventually, for a variety of reasons, Atlantic bluefin tuna did bounce back. For more than four decades, that proposal has shaped how the fish are managed and understood. The only problem is that, as one former delegate put it, the two-stock idea may have only ever been a “convenient fiction.”
Since the 1950s, scientists have broadly accepted that Atlantic bluefin tuna live in two general populations: an eastern stock, which spawns in the Mediterranean Sea, and a western stock, which spawns in the Gulf of Mexico. But a growing body of evidence, including one study published in February 2023, now threatens to upend that binary theory. This developing research points to the existence of a third spawning site in a patch of ocean off North Carolina called the Slope Sea.