A re-evaluation of Atlantic bluefin tuna (Thunnus thynnus) spawning distribution in the western Atlantic Ocean

• Atlantic bluefin tuna spawning patterns evaluated with larval and reproductive data. • Direct evidence of bluefin spawning in multiple areas of the western Atlantic • Northern Gulf and Western Slope Sea the most prominent spawning areas. • Data consistent with a continuous spawning area from the Caribbean to the Slope Sea. • June sampling in the NW Sargasso needed to evaluate continuous spawning distribution. There is currently a lack of consensus on the spatial, seasonal and decadal-scale patterns of Atlantic bluefin tuna ( Thunnus thynnus ) spawning in the western Atlantic Ocean. We compiled ichthyoplankton and reproductive data to characterize bluefin spawning patterns and the uncertainty in these patterns. Ichthyoplankton data indicates that bluefin spawn in the Gulf of America/Gulf of Mexico, northwest Caribbean Sea, north of the Bahamas, along the inshore edge of the Florida Current off the Carolinas and in the western Slope Sea. Reproductive studies identified these same spawning areas, as well as the Windward Passage and waters east of the Bahamas. We used regional sea surface temperature cycles and the distribution of electronically tagged bluefin to identify potentially undocumented spawning areas and times. The northwest Sargasso Sea may also support spawning in June but has not been sampled. Our data is consistent with Atlantic bluefin tuna having a continuous spawning distribution that starts in April in the northwest Caribbean and southern Gulf, progresses through the western Sargasso Sea in June and finishes in early-August in the Slope Sea. The northern Gulf and western Slope Sea are identified as the two most prominent spawning locations across this distribution and spawning in the Sargasso Sea needs to be further evaluated. We could not resolve decadal-scale changes in spawning distribution or timing, but an earlier seasonal timing of optimum temperatures for spawning is evident in all areas. Future work to understand bluefin population structure and migrations will benefit from the data compiled during this study.