Saving Seafood

New Research Reveals Broad Spawning Distribution for Bluefin Tuna

March 13, 2026 — Atlantic bluefin tuna migrate over long distances and spend much of their lives in the open ocean, making them notoriously challenging to study. A question persisted for decades: Where exactly do they spawn in the western Atlantic? Now, new research provides more clarity.

Diving Deep into Seven Decades of Bluefin Tuna Data

Working with partners, NOAA Fisheries scientists did a deep dive into bluefin tuna spawning patterns. They compiled a large dataset from fisheries surveys, archive and museum specimens, and research cruise reports going back to the 1950s. Their analysis included more than 35,000 plankton tows, and they examined nearly 5,000 individual tuna larvae. The results, published in Progress in Oceanography, indicate that bluefin tuna have a much broader spawning distribution than previously recognized. In addition to the known spawning ground in the Gulf of America, bluefin spawn in:

  • Northwest Caribbean Sea
  • North of the Bahamas
  • Blake Plateau
  • Off of the Carolinas shoreward of the Florida Current
  • Western Slope Sea (an area off the Northeast U.S. continental shelf, between the shelf break and the Gulf Stream)

Of these areas, the northern Gulf in the late spring and the western Slope Sea in the early summer produce the most larvae. The results suggest that bluefin spawn in a continuous area during a prolonged spawning season. Spawning starts in April in the southernmost areas—the northwest Caribbean and southern Gulf of America—and ends in early August in the northernmost spawning area, the Slope Sea.

Research fish biologist Dave Richardson, the lead author of the study, explained, “Previous larval studies outside the Gulf of America were often based on a single year of sampling. When we compiled data from many surveys, the consistency was remarkable. When you sample the same area at the same time of year, you consistently find bluefin larvae. This confirmed the pattern we’ve seen in recent years has been going on for a long time. For example, bluefin larvae have been collected from the 1970s through the 2000s in both the Yucatan Channel in the south and the Slope Sea in the north.”

Historically, bluefin tuna have been managed as two stocks—one that spawns in the Mediterranean Sea (the eastern) and the other that spawns in the Gulf of America (the western). Recent larval and reproductive sampling added the Slope Sea to the list of known spawning grounds. Previous research suggests that the populations may mix in the Slope Sea. The scientists conducting this study wanted to know where else bluefin tuna spawn. Mapping all of their spawning grounds is critical to provide a more realistic picture of the population structure. It could also show the extent to which there are unique groups of fish that primarily interbreed with one another.

Read the full article at NOAA Fisheries

Recreational Anglers Help Boost Bluefin Tuna Research

March 2, 2026 — Imagine standing at the stern of a 50-foot fishing vessel. Your legs are pressed up against the gunwale for balance as you rock in the waves and face the churning waters of the boat’s wake. All of a sudden, the reel next to you starts screaming as the mate yells, “Fish on!” Heart racing, you grab the rod and start cranking. It could be a quick 20-minute fight or an intense 5-hour battle to reveal a sleek fish built with more than 80 pounds of muscle. This is what it’s like to be on a trip with the Bacon brothers.

For Brian and Peter Bacon, brothers and seasoned charter captains, the thrill of reeling in bluefin tuna off the Atlantic coast isn’t just about the catch. It’s also about contributing to vital scientific research. Through NOAA’s Cooperative Tagging Center, recreational anglers like the Bacons are providing important data that helps scientists understand the health and movements of bluefin tuna populations. Even when seasons are closed, tagging provides a rewarding mechanism for charter businesses to continue providing a positive experience for paying customers.

What Tuna Tagging Reveals

NOAA’s Cooperative Tagging Center collects crucial information about highly migratory species including bluefin tuna. We work with recreational anglers, charter captains, and commercial fishers along the Atlantic and Gulf coasts—and across the Atlantic Ocean. We tag various species of fish that are difficult to study with other methods. We also provide free tagging kits for anglers to tag fish on their own. When anglers tag a fish, we collect information on fish size, location of capture, and release condition. When a tagged fish is recaptured—days, months, or years later—scientists gain insights into migration patterns, growth rates, and how long these fish live. For instance, some tagged bluefin have been recaptured over a decade after their initial tagging. One of legendary angler Al Anderson‘s fish was caught an astounding 16 years later! These long-term data are critical for assessing geographic range shifts and migratory trends of these important species.

Read the full article at NOAA Fisheries

Longline Sampling Confirms Young Bluefin Tuna Spawn in the Slope Sea

December 5, 2025 — Atlantic bluefin tuna are prized by both recreational and commercial fishermen. In 2022 alone, U.S. commercial fishermen generated an estimated $12.4 million in revenue from harvesting bluefin tuna. However, they are also among the most challenging species to study, as they migrate long distances and live in the open ocean for much of the year.

NOAA Fisheries recently embarked on a cooperative research project to understand Atlantic bluefin tuna reproduction (also known as spawning) in the Slope Sea. Scientists infrequently sample this area of the ocean between the Gulf Stream and the continental shelf of the Northeast United States. It may contain a crucial missing piece for understanding the overall population structure of bluefin tuna in the Atlantic.

Historically, this species has been managed as having two primary stocks:

  • Eastern stock that spawns in the Mediterranean Sea
  • Western stock that spawns at older ages in the Gulf of America

Dr. Molly Lutcavage’s lab at the Large Pelagics Research Center in Gloucester, Massachusetts is conducting research on reproduction and electronic tagging. The lab is affiliated with UMass Dartmouth’s School for Marine Science & Technology. Their research suggested that spawning might be occurring in other areas of the western Atlantic as well, and by younger, smaller fish. Lutcavage’s lab predicted that smaller fish would spawn closer to feeding grounds. Biological evidence from NOAA Fisheries larval fish sampling in the Slope Sea supported this hypothesis. Recent genetic research shows the stocks are interconnected. However, there was little data available on the reproductive condition of adult bluefin tuna, including smaller adults, in the Slope Sea to corroborate these studies—until now.

Read the full article at NOAA Fisheries

Scientists study Atlantic bluefin tuna spawning off Northeast U.S.

October 10, 2025 — Scientists are getting closer to understanding how Atlantic bluefin tuna spawn between the Gulf Stream and the continental shelf off New England, possibly a third important breeding area in addition to the Gulf of Mexico and Mediterranean Sea.

The Slope Sea off the Northeast U.S. coast has been studied over the past decade in the belief it contributes to bluefin tuna stock mixing between the two long-known east and west breeding populations.

During summer 2025 scientists with the National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center conducted two exploratory surveys to examine how bluefin tuna use this area for reproduction. A cooperative survey with commercial longline fishermen sought adult spawning tuna, and a second survey soon after sampled Northeast waters for bluefin tuna larvae.

Read the full article at the National Fisherman

Genomics Help Uncover Mysteries of Atlantic Bluefin Tuna

September 19, 2025 — The Slope Sea may hold a key to better understanding Atlantic bluefin tuna. 

This summer, scientists journeyed to the Slope Sea on two exploratory surveys to examine how Atlantic bluefin tuna use this area for reproduction (also known as spawning). The first survey was a cooperative longline survey to look for spawning fish. The second survey followed closely on their heels to look for the results of that spawning—larval, or baby, bluefin tuna.

The objective was to document the potential contributions of spawning between the Slope Sea and other spawning areas like the Gulf of America. Next they will analyze DNA from both larval and adult bluefin tuna to estimate the population (stock) size. Atlantic bluefin tuna has been managed as having two primary stocks—one that spawns in the Mediterranean Sea (the eastern) and the other in the Gulf of America (the western). Recent research suggested the Slope Sea could be a major spawning ground comparable to the Gulf of America. Genetic research has shown the two stocks are interconnected. This year’s survey aims to clarify remaining uncertainties about bluefin tuna stock structure and spawning dynamics.

Read the full article at NOAA Fisheries

Scientists baffled by disturbing behavior shift in tuna — here’s what you need to know

August 21, 2025 — A researcher at the University of Maine’s Pelagic Fisheries Lab conducted a study about Atlantic bluefin tuna and observed surprising changes in the fish’s diet.

This prized species of fish is shifting away from eating herring and now consuming menhaden as its primary prey.

What’s happening?

As the university shared on Phys.org, researcher Sammi Nadeau published the study in the journal Marine Ecology Progress Series.

Atlantic herring in the Gulf of Maine have been dramatically declining in population. Without ample herring to eat, Atlantic bluefin tuna began eating another fatty pelagic fish, menhaden.

Menhaden is not only a primary food source now for Atlantic bluefin tuna but also an essential ingredient in commercial fish oils. Understanding how vital menhaden have become commercially and in the natural food chain, scientists are recommending fishing limits to reduce the burden on menhaden populations.

Read the full article at The Cool Down

Atlantic bluefin tuna diets are shifting in a changing Gulf of Maine

August 11, 2025 — Maine’s coastal communities have been hooked on the Atlantic bluefin tuna since at least the late 1880s—first as bycatch, until the 1930s when the fish became a prized target in fishing tournaments. Through the subsequent decades, bluefin tuna have and continue to support working waterfronts in Maine and beyond.

Despite a decline in prices, a single bluefin tuna can land over $10,000, and in 2024 alone, the National Oceanic and Atmospheric Administration reported that commercial and recreational landings exceeded 3.5 million pounds, fueling a range of economic activities from food markets to boat building and gear sales.

Sammi Nadeau (’18, ’21G), the lab manager at UMaine’s Pelagic Fisheries Lab, conducted a study recently published in the journal Marine Ecology Progress Series that illustrated a shift in the tuna’s diet and described the role of foraging in the tuna’s lifecycle.

“You can imagine that those migrations from across the ocean and things like reproduction are extremely energetically demanding,” said Nadeau, “So being able to get a really good meal, fill back up and get ready to go back across the ocean is important to fulfill their life history.”

Read the full article at the PHYS.org

Bluefin Tuna Get It On off North Carolina

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.

Read the full article at Hakai Magazine

Walmart, Sam’s Club strengthen tuna-sourcing requirements

June 20, 2023 — Walmart is updating is seafood sourcing policy to require tuna suppliers to source exclusively from vessels that have 100 percent observer monitoring – either electronic or human observer – by 2027.

The Bentonville, Arkansas, U.S.A.-based operator of more than 10,500 stores globally, including nearly 4,700 Walmart stores and nearly 600 Sam’s Club stores in the U.S., said tuna suppliers must also source from fisheries using zero high seas transshipment, unless the transshipment activity is covered by 100 percent observer monitoring by 2027. The changes apply to Walmart U.S., Walmart Canada, and Sam’s Club stores.

Read the full article at SeafoodSource

Tuna species productivity and size may decrease due to climate change

March 1, 2023 — Understanding how climate change and fishing pressure affect major commercial species productivity and body size is key to being able to adapt and ensure the future sustainability of the fisheries.

In this context, a team from Spain’s Ciencia y tecnología marina y alimentaria (AZTI) has coordinated a study, published in Global and Planetary Change, in which the projections in  and swordfish productivity and body size in the future under different climatic and fishing scenarios have been analyzed. A model that includes many mechanisms that represent the population dynamics of different species and the competition between them has been used for this purpose.

“We wanted to know how the climate change and fishing pressure is going to impact some of the most commercially important species in order to make decisions to ensure the future of the resources,” says Maite Erauskin-Extramiana, the AZTI researcher who led the study.

Read the full article at PHYS.org