An independent study, funded in part by the Department of Commerce's National Oceanic and Atmospheric Administration's National Marine Fisheries Service, improves scientists' understanding of the migratory habits of one of the world's most valuable marine fish, the Atlantic bluefin tuna. NOAA fisheries managers believe the study, which tracked giant bluefin tuna throughout the north Atlantic Ocean, provides data which can strengthen international management measures.

The study reported in the August 17 issue of the journal Science, with noted tuna researcher Dr. Barbara A. Block of Stanford University as lead author, provides significant insight into the migration patterns of these giant fish. This five year study was co-authored by Dr. Eric D. Prince of NOAA fisheries.

"The study confirms and expands on past migration-related traditional tagging data and provides a wealth of new knowledge about the diving patterns, thermal biology, feeding characteristics and environmental preferences of Atlantic bluefin tuna," said Bill Hogarth, acting NOAA fisheries director. "We are pleased to be a part of this important research that gives scientists and managers a clearer picture of the migratory, feeding and spawning habits of these fish."

Block and her team of researchers used two new state-of-the-art electronic tags to monitor the movements of the fish. This group of scientists assisted in the development of a new generation of electronic tags initiated with a grant from NOAA fisheries. Using a combination of satellite pop-up tags and archival tags, scientists were able to track the tuna's migration and monitor several behavioral activities. More information about the archival and pop-up tags is available at http://www.montereybayaquarium.org/aa/aa_pressroom/aa_pkits_newsreleases.asp.

NOAA fisheries managers are particularly interested in the newly reported data because of their implications for future management decisions. An accompanying article, also in the Aug. 17 journal Science, titled "Whose fish are they anyway?" and co-authored by NOAA fisheries' Northeast Fisheries Science Center director Dr. Michael Sissenwine, examines this controversial marine fishery. Journalists may receive a copy by e-mail from: scipak@aaas.org. Subscribers may access the article at http://www.sciencemag.org. The public may obtain the article by calling (202 326-6450.

Bluefin tuna in the Atlantic are highly sought after because they are prized by recreational fishermen and they have a high commercial value in Asian sushi and sashimi markets, with some fish going for as high as $60,000. Harvesting of bluefin and other Atlantic tuna is managed through catch quotas established by agreements of member countries through the International Commission for the Conservation of Atlantic Tunas based in Madrid, Spain. Currently, bluefin tuna are managed as two separate stocks, eastern and western. The western stock, the smaller of the two, has tight restrictions placed on it. The larger eastern stock has fewer restrictions. While scientists have been aware of mixing of the stocks in international waters, where many countries fish, the nature of mixing has not been well studied until now.

"The U.S. and its recreational and commercial fishing groups, along with environmental and conservation organizations, has long supported the need to rebuild Atlantic tunas through international agreement and compliance," said NOAA fisheries' Director of the Office of Habitat Conservation, Rolland Schmitten, who is the U.S. ICCAT commissioner. "We've seen that effective science and management in the international arena have arrested the decline of the western Atlantic bluefin tuna stock. The Block study is a critical link in the knowledge we need to ultimately rebuild the stock throughout the Atlantic. This science reaffirms that the level of harvest of eastern Atlantic and Mediterranean bluefin tuna is excessive and must be reduced, and that management measures in the east can affect the west."

At the request of the United States, ICCAT is already moving forward with two stock mixing issues. ICCAT members have endorsed new research on bluefin tuna in the central Atlantic to collect biological samples of spawning size bluefin tuna in the Mid-Atlantic ocean to help determine if there is a spawning area there. ICCAT scientists will review recent studies, including the Block study, and prepare recommendations on how best to account for the new mixing data on bluefin tuna in future stock assessments and management decisions. Their recommendations will be presented to the full ICCAT scientific body in October and to the ICCAT commissioners in November.

In the Block study, researchers discovered that Atlantic bluefin often are traveling throughout the entire North Atlantic and, in some cases, into the Mediterranean Sea. Individual tuna also migrated from the Western Atlantic to the east and back again in the same year. The Science article reported that the western-tagged bluefin travel to distinct spawning grounds in the Gulf of Mexico or the Eastern Mediterranean. "The results indicated that western-tagged bluefin are vulnerable to fishing from all Atlantic bluefin tuna fisheries," the authors report.

For more information about the Block study, go to: http://www.stanford.edu/dept/news/report/.

NOAA Fisheries is dedicated to protecting and preserving our nation's living marine resources through scientific research, management, enforcement, and the conservation of marine mammals and other protected marine species and their habitat. To learn more about NOAA fisheries, please visit http://www.nmfs.noaa.gov.