Atlantic Bluefin Fisheries Aided by New Science

Atlantic bluefin tuna stocks have been on the increase. Keith Alexander Lee

The rebound of Atlantic bluefin tuna is a great success story for modern fisheries management. With the prevalence of school-sized bluefins off the Northeast and Mid-Atlantic coasts over the last couple of years—and recreational regulations that might seem unnecessarily strict—we checked in with NOAA Fisheries to find out what rapidly advancing science is learning about an internationally managed fishery that spans oceans and continents.

“The science indicates that there are more bluefin tuna in the ocean than at any time in the past 50 years,” said Dr. John Walter, Deputy Director for Science and Council Services at NOAA’s Southeast Fisheries Science Center. Walter is a delegate to the International Commission for the Conservation of Atlantic Tunas (ICCAT). More than 50 nations and contracting parties make up this body that regulates Atlantic bluefin fisheries.

Current Management Structure

ICCAT recognizes two stocks of Atlantic bluefin tuna and manages them separately. The eastern Atlantic stock off Europe (including the Mediterranean Sea) and the western Atlantic stock off the U.S. and Canada (including the Gulf of Mexico) each have their own management measures and catch limits.

“Research shows there is extensive mixing of the two stocks in the Northwest Atlantic Ocean, and demonstrates that eastern Atlantic fish make up to 65 percent of bluefin tuna in the west,” Walter said. ICCAT is locked into a pre-agreed regulatory framework for actions, such as setting catch limits, in order to provide stability in international fisheries. The two stocks are managed in conjunction with consideration of the latest scientific data, Walter said. 

In recent studies, a new genetic research technique known as close-kin mark-recapture (CKMR) produced western Atlantic bluefin abundance estimates substantially higher than traditional data ICCAT had been using to manage the fishery. Walter said abundance has continued to increase in recent years.

As a result, a 17 percent increase in total allowable catch was secured for U.S. fishermen for 2026-2028. Walter said it is the largest single-year increase in the 45-year history of ICCAT’s binding catch advice. CKMR data is being used to assess stocks, and a review of management procedure begins next year.

Our Piece of the Pie

How will this increase affect recreational anglers in the U.S.? Well, at presstime, NOAA Fisheries had proposed rulemaking to increase quota for the commercial and recreational sectors according to allocation percentages, said Walter. This will make more fish available for U.S. fishermen.

When new quotas are implemented, it will hopefully provide some relief to frustration experienced over early recreational closures like we’ve seen in recent years. The season length, however, depends on how good the fishing is and how quickly quotas are met.

The fishing has been very good for recreational anglers lately because huge numbers of school-sized (27- to 47-inch) bluefin tuna have been feeding close to the coast. Walter said one strong year class dominated the 2024 and 2025 landings. Those fish should grow into the large school category (47 to 59 inches) this year. 

“The high availability of fish to the recreational fishery may also be due to the fish staying relatively close to the shore for large portions of the year, likely due to the availability of baitfish like sand eels and menhaden,” Walter explained.

The U.S. has about 49 percent of the western Atlantic total allowable catch (Japan has 25 percent, Canada has 20 percent). The recreational share of the current U.S. quota is about 22 percent by weight. However, the number of bluefin caught by recreational anglers can more than double the number of commercially harvested fish because anglers target smaller tuna. In 2026, properly permitted recreational boats were allowed two 27- to 73-inch bluefin per trip. They are allowed just one per year longer than 73 inches.

Scientific Breakthrough

Regulatory change in international fisheries happens slowly by design, and there’s still a lot science doesn’t know about Atlantic bluefin tuna. Currently, holes in our knowledge are filling rapidly.

Walter said NOAA Fisheries views CKMR as a major advancement that the ICCAT scientific committee called a “breakthrough.” Through genetic samples, larval tuna are linked to their parentage. Later sampling of adult tuna provides a ratio of adults and larvae that are genetically linked. From the Gulf to New England and Canada, “recaptures” can detect parentage months or years later. The ratio is used to determine total abundance of bluefin tuna. “It is similar to genetic testing that people use to determine ancestry, but for fish,” Walter said.

And CKMR has more to teach us than how many tuna are in the ocean. Major bluefin spawning grounds were documented in the Gulf and Mediterranean long ago. A third spawning ground in the Slope Sea has long been suspected. Last year, NOAA research aboard a commercial longliner documented spawning in this region of the Atlantic between the Gulf Stream and continental shelf off the coast of the Northeast. A couple weeks later, thousands of bluefin larvae were collected from the same area.

“We will determine if these samples confirm spawning by young adult bluefin in the Slope Sea,” Walter said. “Combined with new methods of close-kin mark-recapture, this effort will help us understand how bluefin tuna use the Slope Sea for spawning, and the resulting impacts on population dynamics.”

Walter added that a deep dive of data going back to the 1950s reveals a potential continuous bluefin spawning area from the northwest Caribbean to the Slope Sea.

Read Next: Targeting Bluefin Tuna in the Spring

Call to Action

CKMR research on Atlantic bluefin tuna is an international effort between U.S. and Canadian scientists, with expertise lent by Australian scientists who’ve been using the technique to study endangered southern bluefin tuna for years.

NOAA also works with recreational and commercial interests to tag and sample. For the average angler, proper licensing and reporting of recreational catch are essential to inform decision making.

If you’re an angler who wants to take it a step further, tagging kits are available through NOAA’s Cooperative Tagging Center (email: [email protected]) and/or you can participate in genomic studies by collecting fin clips for the University of Maine Pelagic Fisheries Lab’s Genetics for Giants to Juvies program (umaine.edu/pelagicfisherieslab).

In the end, a sustainable Atlantic bluefin fishery—and our access to it—relies on accurate data being fed into a massive and slow-moving international management process. Hang in there, new science and a booming fishery seem to be dragging us in the right direction. 

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