Thin Tuna

Giant bluefin tuna in the Gulf of Maine have declined in numbers and overall health since the 1990s, finds a recent study.

Walter Golet, of the University of New Hampshire's Large Pelagics Research Lab, and colleagues analyzed the fat and oil content and body shape of more than 3,000 Atlantic bluefin tuna (Thunnus thynnus) at the Yankee Fisherman's Co-op in New Hampshire.

In addition to injecting flavor into sushi, fat content indicates the overall health of this migratory fish. The bluefin travel more than 1,000 miles (1,600 kilometers) from their spawning grounds to the Gulf of Maine. The long trek makes for lean low-quality fish at the time of their arrival in the Gulf in June. However, the researchers found that the quality of bluefin caught in August and September after several months at the Gulf of Maine’s buffet table has declined.

The probability of catching a poor-quality fish (grade "C" or worse, with "A" being high-quality) in June 1991 was 30 percent compared with 70 percent in 2004. Good quality fish, such as B or better, now comprise less than one percent of the commercial catch at this New Hampshire cooperative.

The findings, published this week in Fishery Bulletin, indicate potential changes in food sources, shifts in migratory patterns, or the impact of fishing may be the cause of this decline.

Golat doesn't expect to find a single smoking gun. “I’m very convinced that it’s multiple factors working with each other,” Golat said.

—LiveScience Staff

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