Magazine article Science News

Where Tuna Go: Atlantic Fish Mix for Feeding, Not Spawning

Magazine article Science News

Where Tuna Go: Atlantic Fish Mix for Feeding, Not Spawning

Article excerpt

The largest high-tech tag study yet of Atlantic bluefin tuna suggests that two groups mix on feeding grounds but spawn on opposite sides of the ocean. This finding indicates that fishing regulations need to change, say the researchers who tagged and tracked hundreds of the fish.

Bluefin tuna counts in the western Atlantic plummeted decades ago and haven't recovered, despite conservation measures, says Barbara Block of Stanford University. Estimates are that 25,000 fish remain. Block and her colleagues say that their new evidence supports the idea that tuna populations travel widely but spawn only at the edge of the continental shelf in the Gulf of Mexico or at a site in the Mediterranean Sea.

"The data's very exciting," comments Molly Lutcavage of the University of New Hampshire in Durham, who leads another group of tuna taggers.

A big advance in studying tuna came with the development of electronic tracking devices. In the April 28 Nature, Block and her colleagues report information from 330 Atlantic tuna tracked electronically for up to 5 years.

A report from this project in 2001, with data from about 50 fish, said that the tuna swam unexpectedly long distances, even crossing the Atlantic (SN: 8/18/01, p. 101).

The new work continues to support the idea that fish from the east and west mingle in feeding grounds. The team now reports that 26 tuna tagged in the western Atlantic migrated all the way to the Mediterranean. …

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