Bluefins Cross Management Boundaries

Atlantic bluefin tuna can reach sizes of 10 feet in length, weighing as much as 1,500 pounds. They are also trans-oceanic travelers, capable of crossing the Atlantic Ocean basin in 40 days. In fact, these big, fast-moving fish are routinely crossing management boundaries, a study in the 17 August 2001 issue of Science shows.

The findings suggest the need to reassess ocean-wide management policies.

Barbara A. Block of Stanford University, in collaboration with the Monterey Bay Aquarium and the National Marine Fisheries Service, equipped 377 western Atlantic bluefins with surgically implanted archival tags and pop-up satellite tags, some capable of detaching from the fish, surfacing and sending information to orbiting satellites. Fishers from seven nations recaptured 49 fish (18 percent) with archival tags.

Of these, 31 were recaptured in eastern Atlantic or Mediterranean fisheries. Some 69 percent were recaptured in the western Atlantic off Cape Cod, Maine, and in the Gulf of Mexico. Younger bluefins in western Atlantic waters seem to stick close to home, then venture to the East Atlantic and back, or into the Gulf of Mexico to breed as they reach sexual maturity.

"The results," the Science paper concludes, "show that western-tagged bluefin are vulnerable to fishing mortality from all Atlantic bluefin tuna fisheries." Current regulation divides the Atlantic along the 45-degrees-W meridian, separating the North American coast from the eastern territory, where fishing quotas are larger.

Block's findings are addressed by John J. Magnuson of the University of Wisconsin, Madison, and colleagues, in a related Science essay.

-- Becky Ham