Evidence supports classification of a major Atlantic bluefin tuna spawning ground off the northeastern United States

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Bluefin tuna are the largest of all tuna species – adults can reach ten feet in length and weigh over a thousand pounds. But they start out small, as larvae 2 to 3 millimeters long. This one was captured by Chrissy Hernandez in the Slope Sea, a region of the Atlantic Ocean between the US continental shelf and the Gulf Stream further offshore. The area is a newly recognized spawning ground for western Atlantic bluefin tuna – good news for a species whose population in the Gulf of Mexico is sustainably managed with limited harvest. Credit: Chrissy Hernandez, Woods Hole Oceanographic Institute

The Slope Sea off the northeastern United States is a major spawning ground for Atlantic bluefin tuna (Thunnus thynnus), claims a new paper. This finding likely has important implications for the population dynamics and survival of this fish, according to the article, “Support for the Slope Sea as a major spawning ground for Atlantic bluefin tuna: evidence from larval abundance, growth rates, and particle-tracking simulations”, published in the Canadian Journal of Fisheries and Aquatic Sciences.

“Overall, our results provide important supporting evidence that the Slope Sea is a major spawning ground likely to be important to population dynamics,” the paper says. Spawning in the Slope Sea “may provide the species with additional resilience in the face of both harvesting and climate change,” the paper adds.

The paper presents larval evidence supporting the recognition of the Slope Sea as a major spawning ground, including that larvae collected from the Slope Sea grew at the same rate as larvae collected from the Gulf of Mexico, indicating that this region is a good larval habitat.

“Compared to everything we know about this species, the Sea Slope is a perfectly good place to be born as a larva,” said lead author Christina Hernández, who was a PhD student at the Massachusetts Institute of Technology (MIT) – Woods Hole Oceanographic Institution (WHOI) Joint Program in Oceanography / Applied Ocean Science and Engineering at the time of the study.

“The larvae grow at a similar rate in the Slope Sea as they do in the Gulf of Mexico, at least year round. [of sampling]suggesting that the Slope Sea provides quite suitable and adequate habitat for larval growth and development,” she said.

The researchers used plankton nets to collect larvae from the Slope Sea and the Gulf of Mexico, and they analyzed and compared larval growth in the two regions by studying larval otoliths, which are small bones found in the heads. of tuna. The researchers also performed larval transport simulations to estimate the movement of larvae floating in ocean currents forward and backward over time to assess the origin of the larvae and their fate.

Evidence supports classification of a major Atlantic bluefin tuna spawning ground off the northeastern United States

Bluefin tuna larvae are 2 to 3 millimeters long when they hatch, but they can grow rapidly, adding about 0.5 millimeters per day. Credit: Chrissy Hernandez, Woods Hole Oceanographic Institute

The prevailing interpretation is that Atlantic bluefin tuna comprises two populations with strong natal migration to spawning grounds in the Gulf of Mexico and the Mediterranean Sea. However, there has long been speculation that spawning may be taking place in other areas, and a 2016 paper demonstrated a bluefin tuna spawning ground in the Slope Sea. The Slope Sea is a wedge of ocean bounded by the breakup of the American Shelf and the Gulf Stream as it moves away from the eastern seaboard of the United States.

“In the 2016 paper, we proposed that the Slope Sea is a third major spawning ground for bluefin tuna. Additional sampling, reported in this new paper, confirmed that the abundance of bluefin tuna larvae in the Slope Sea is comparable to levels typically found in the Gulf, and bluefin tuna larvae in the Slope Sea have been found to grow at similar rates to those in the Gulf of Mexico,” said researcher David Richardson. in Fisheries Biology at the National Oceanic and Atmospheric Administration (NOAA).Richardson is senior author of the 2016 paper and co-author of the new paper.

“This work underscores the importance of the Slope Sea as a spawning ground and underscores the need for continued bluefin tuna research in this region,” Richardson said.

The paper notes that the response to the discovery of the Slope Sea spawning ground has been mixed, with some scientists expressing skepticism about the origin of the larvae or stating that classifying Slope Sea as a spawning ground was premature.

Further study of larvae and breeding adults in the region should be prioritized to support management decisions,” the document states.

“We need as much information as possible about bluefin tuna in order to improve management models and improve the sustainable management of our fisheries,” Hernández said. “I hope this study will help get greater recognition of the Slope Sea as a spawning ground and more funding for further research in this area.”


Potential Western Atlantic spawning area discovered for Atlantic bluefin tuna


More information:
Christina M. Hernández et al, Support for the Slope Sea as a major spawning ground for Atlantic bluefin tuna: Evidence from larval abundance, growth rates, and particle tracking simulations, Canadian Journal of Fisheries and Aquatic Sciences (2021). DOI: 10.1139/cjfas-2020-0444

Provided by the Woods Hole Oceanographic Institute


Quote: Evidence strengthens classification of a major spawning ground for Atlantic bluefin tuna off the northeastern United States (2022, March 4) retrieved March 4, 2022 from https://phys.org/news /2022-03-evidence-bolsters-classification-major-spawn.html

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