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.