Study: Tuna on the decline

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Study: Tuna on the decline
Over-fishing, global climate change blamed


August 27, 2007 6:00 AM
DURHAM (AP) — The number and quality of giant bluefin tuna are declining in the Gulf of Maine, endangering the popular catch, according to University of New Hampshire researchers.
Their study does not pinpoint why the number of bluefins is falling dramatically or why the remaining fish are getting slimmer, but the researchers suspect a number of factors, including over-fishing from European countries in the Eastern Atlantic and the Mediterranean Sea and shifts in migration and foraging patterns due to global warming.
In the mid-1990s, UNH scientists documented 500 to 900 schools of bluefin tuna in the Gulf of Maine averaging 100 to 150 fish each, said Molly Lutcavage, director of UNH's Large Pelagics Research Center. She said only a "few" schools would be seen in today's waters.
"The horrifying reality is that the huge decline in abundance happened so quickly," she said.
The toll is evident in the number of commercial tuna fishing permits, said Rich Ruais, executive director of the East Coast Tuna Association, who estimates that in the mid-1990s, there were 15,000 permits from Maine down to Texas, where today there are about 4,400.
With relatively low fishing quotas strictly enforced in the Western Atlantic, many point to Eastern Atlantic and Mediterranean fishermen for the decline in stocks.
Atlantic bluefin tuna are known for being highly migratory, with spawning grounds in the Gulf of Mexico and the Mediterranean. Tagging from UNH scientists has shown the fish travel long distances, often mixing with stocks in the Eastern Atlantic.
Bob Campbell, of Yankee Fisherman's Co-Op in Seabrook, kept track in a log book of the 3,082 bluefin tuna he handled, providing the researchers a unique record of their numbers and quality.
"In a drawer, he had two or three notebooks with every fish he graded in the last 14 years, from 1991 to 2004," said UNH graduate student Walter Golet. Golet's findings corroborated observations by fishermen, brokers and cooperative managers that the quality and quantity are declining.
Golet's research showed that a fish caught in September 1991 had only a 9 percent chance of being a C+ grade, with A being the highest, based in part on fat content. In contrast, a fish caught in September 2004, even after a season of feeding in the Gulf of Maine, had a 76 percent chance of being a C+.
The fat content is not just important for taste. The researchers say it's an indicator of the overall health of the bluefin and of its future.
"One of the big consequences of not fattening as much is the potential impact it could have on reproduction," Golet said. "Reduced energy stores can often force a fish to skip spawning in a particular year."