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Tuna Catch Becomes Leaner
August 22, 2005
SEABROOK, N.H.—Bluefin tuna caught in the Gulf of Maine these days are a lot leaner than they were in the 1990s, suggesting a major shift in the ecosystem, according to scientists at the University of New Hampshire.
Fourteen years worth of records at a Seabrook auction house reveal that tuna aren’t eating as well as they used to, says Molly Lutcavage, director of the Large Pelagics Research Lab at UNH. Bluefin are also less abundant.
Lutcavage says it’s unclear what has happened to the species, a top predator in the Gulf of Maine and the premium tuna for sushi lovers in Japan.
The decline, she says, could signal changes in the gulf that also may be affecting whales, seabirds and other fish that feed on the same forage fish, such as herring. Many tuna fishermen say they are seeing a lot fewer tuna in near-shore waters and also fewer whales and seabirds.
The findings of the UNH study also could influence the debate over whether there should be restrictions placed on the large midwater trawlers that fish for herring in the gulf, especially near shore.
The research is based entirely on the records kept by one man, Bob Campbell, manager of the Yankee Fisherman’s Cooperative in Seabrook.
Trained by the general manager of a Japanese auction house, Campbell grades each fish on freshness, oil content, color and shape. He also records the weight and date the fish was caught.
Because grading practices can vary depending on who’s doing the grading, Campbell’s records—which are kept in spiral-bound notebooks and date back to 1991, are valuable to scientists because they are so consistent, Lutcavage says.
The high oil content that makes tuna so tasty to Japanese palates is the best indicator for the overall health of tuna.
Fishermen seek oil-rich tuna because they fetch the highest prices. David Linney, 63, a Maine tuna fishermen in York, says the tuna caught in the early 1990s were so oily that they would slide around the deck when he tried to dress them, and he had to wash his hands for a long time afterward to get the oil off.
Today, he says, most fish have so little oil that he can clean his hands with one rinse. “It’s very hard to catch a real butterball now, even late in the season,” he said.
With their torpedo shape, Atlantic bluefin are built for speed. They can grow to be close to 12 feet long, and can weigh more than 1,500 pounds. They come to the Gulf of Maine in late May to fatten up, and they depart for warmer waters by the end of October. Some travel to the Gulf of Mexico, and some go elsewhere in the Atlantic, but it’s not clear where, Lutcavage says. It’s possible that some migrate to European waters, where they are heavily fished, she says.
Tuna are primarily caught in the Gulf of Maine in near-shore waters by small boats on day trips. Fishermen use harpoons and fishing rods. Farther offshore, fishermen also use purse seines. They surround schooling fish with a net and trap them by closing the bottom of the net.
Some fishermen use an electrified harpoon so they can kill the fish instantly, thus assuring a better quality meat and a higher price. The meat of a tuna that dies when stressed, such as during a struggle to escape a fishermen’s line, is more watery because the cell structure degrades, according to Jamie Foote, a fish-buyer from Boston.
In Japan, the bluefin caught in the Gulf of Maine is a delicacy known as “Boston bluefin.” When the Japanese economy was booming in the early 1990s, fishermen in New England were getting as much as $25 a pound for their tuna.
But an economic downturn in Japan led to lower demand. In addition, supply has increased with the introduction of tuna farms in Australia, Croatia, Malta, Morocco, Spain, Portugal, Japan and Mexico. The fish farms fatten tuna that is caught in the ocean.
At the Fisherman’s Cooperative, bidders inspect the tuna, grade them and make silent bids on a slip of paper. Campbell, who represents fishermen’s interests at the auction, grades each tuna to assure the integrity of the system. He won’t show his grades to anyone until after the auction is over.
At an auction Friday, the top quality tuna sold for $4,800, or $10.64 a pound, which these days is considered a high price. All three tuna sold Friday were bought by Foote for the U.S. market, which has increased in recent years in part because of the influx of Asian immigrants.
Between 1991 and 2004, Campbell graded 3,834 tuna. Researchers who analyzed his records found that fish are arriving in the gulf in June in poorer condition than they did in the early 1990s, and that those caught later in the season have a lower oil content and slimmer body shapes.
The study shows a steady decline in oil content since 1991, with the steepest decline occurring between 1992 and 1995.
“What amazed all of us, the results were so consistent, that the decline in every feature of condition was documented in every aspect of the quality of the fish,” Lutcavage said.
Campbell, who lives in Kennebunk, says he never knew his records could be helpful to scientists. He says the results confirm what he already knew.
“When I first started, at the end of September and October the fish were of really great quality, lots of fat and nice color,” he said. “That’s a thing of the past.”
The researchers have yet to publish the study, but they believe the findings are so significant that they decided to make the facts public before submitting the paper for publication, Lutcavage says.
John Annala, chief scientist at the Gulf of Maine Institute in Portland, says there has been an apparent shift in the distribution of bluefin tuna, and also right whales, in the gulf. He says scientists need to find out what is causing the shift.
He says the nutritional value of the tuna’s key forage fish, herring, may have declined. Both right whales and herring feed on Calanus, a zooplankton, so perhaps the distribution of Calanus has changed, he says.
Masa Ota, a Portland-based buyer for the Japanese market, says he believes the tuna quality is down because tuna is over-harvested.
He says purse seines are able to catch entire families, a harvest method that may be very disruptive.
The issue is not confined to the Gulf of Maine. Over the past four or five years, Canadian scientists have observed a decline in the quality of bluefin tuna caught in the Gulf of St. Lawrence, says John Neilson, a scientist with the Canadian Department of Fisheries and Oceans.
He says food does not appear to be the cause because herring and mackerel seem abundant.
Linney, the York fisherman, points to the herring trawlers as a major factor, noting that trawlers began fishing in the area in 1994. Now, he says, there is simply not enough herring left to support seabirds, whales and tuna.
“It appears the area will not hold giant bluefin tuna any longer,” he said.