Fishermen who harvest bluefin in the northwest Atlantic, including those from the United States, Canada and Japan, regularly adhere to quotas. In fact, the United States does not catch enough bluefin tuna to meet its quota, and allows other countries to make up the difference.
In contrast, European vessels routinely disregard quotas, and the rampant overfishing is threatening to cause a collapse of the stock, officials said.
William Hogarth, director of the National Oceanic and Atmospheric Administration, plans to ask the international body that regulates tuna fishing for a three- to five-year moratorium in the eastern Atlantic and Mediterranean Sea next month.
"Basically that's where the situation is worse in terms of overfishing," said Monica Allen, a spokeswoman for Hogarth. "The concerns are that we've tried, but failed, to get the reasonable fishing needed to help rebuild the stock."
Hogarth, representing the United States, chairs the International Commission for the Conservation of Atlantic Tunas, the body that studies a number of tuna species and issues recommendations to its members regarding the health, strength and migration of the stocks.
The group is made of 44 countries and the European Union, according to its Web site. Many EU countries are also members independently.
Allen said studies are beginning to show the western stock, which spawns in the Gulf of Mexico, and the much larger eastern stock, which spawns in the Mediterranean, mingle much more than previously thought.
"The problem will affect the western stock because some of what our fishermen are fishing is coming from the eastern stock," she said. "If that one is overfished, it will have an echo effect off our coast. It'll have a bigger effect than vice versa because the Mediterranean stock is about 10 times the size of ours.
In a letter posted on NOAA's Web page, Hogarth said European quotas, which had been set at 32,000 metric tons per year, are consistently disregarded, and that European vessels have landed more than 18,000 metric tons per year over their quota.
This year, their quota is 29,900 metric tons.
"With such unrestrained fishing, it is no surprise that ICCAT's scientists are warning of stock collapse," Hogarth wrote.
Unless eastern Atlantic and Mediterranean tuna fishermen adhere to their quotas, western tuna stocks could be adversely affected.
"There is a very real concern that the long-term poor management in the eastern Atlantic and Mediterranean bluefin tuna fishery is negatively impacting the much smaller western Atlantic bluefin tuna stock due to mixing of the stocks," he said.
According to the European Union's fisheries Web page, the union adopted a 15-year plan for "the gradual recovery of bluefin tuna and, also importantly, for the sustainability of the fisheries, the fleets and the coastal communities involved." The plan includes a reduction in the allowable catch from 32,000 metric tons to 25,500 metric tons by 2010.
American tuna fishermen, however, believe the EU is unable or unwilling to enforce its quotas.
"I worked over there for 11 years and there's no government oversight over what is being caught in Italy," said Mark Godfried, a former fisherman and current adviser to fishing businesses. "It's a wide open fishery."
He said while he supports the idea of a moratorium, a better route would be to establish and enforce a workable quota system in the eastern Atlantic and Mediterranean Sea.
"You can pass all the moratoriums you want, but do you think (Libyan ruler Moammar) Gadhafi is going to stop fishing?" Godfried said. "How is Hogarth going to enforce that?"
A recent study released by the University of New Hampshire, confirming fishermen's anecdotal observations, shows that the tuna caught over the last few years tend to be thinner and of lesser quality.
The study suggests several reasons, which many tuna fishermen agree with, that could be responsible for or could be combining to create the decline, including tougher competition from trawlers and from marine predators foraging for food in New England waters, changes in spawning grounds because of ocean temperature and current changes, and overfishing in the eastern Atlantic Ocean and the Mediterranean Sea that is sending some bluefin west.
Bluefin caught from September through the end of this month are supposed to be the fattest and most valuable, but the UNH study concluded, using catch data from the Yankee Fishermen's Cooperative in Seabrook, N.H., that the likelihood of catching a top-grade bluefin in September slid from 60 percent in 1991 to about 20 percent in 2004.
However, the probability of catching one of lesser quality, meaning it has less fat and oil, in September jumped from 15 percent in 1991 to almost 80 percent in 2004.
The minimum length of a bluefin tuna commercially landed is 73 inches, which takes a bluefin about seven years to achieve.
Recent studies have also found more tuna are migrating west across the Atlantic than previously thought. The UNH study noted that tuna swimming such long distances are bound to be leaner when caught.
The UNH study's authors found "highly significant declines in the fat and oil content and shape of northern bluefin tuna landed in the Gulf of Maine over the last 14 years, corroborating the observations of fishermen. Northern bluefin tuna arrive in leaner condition and are not increasing their fat stores on the feeding grounds as they did in the early 1990s. This was particularly true in late summer and early fall, when fish usually fatten and become more rotund."
Godfried and other fishermen also believe the introduction of midwater trawlers, large vessels that pull cone-shaped nets behind them to catch herring, mackerel and other pelagics, that year is at least part of the reason bluefin tuna have declined. Tuna, along with many other sea creatures, feed off herring and mackerel.
Tuna fishermen have been pushing for midwater trawling bans for years and recently succeeded in obtaining a summertime ban in a parcel of ocean stretching from Cape Cod Bay to the Canadian border known as Area 1A. Canada has an outright ban on midwater trawling, but does allow one research trawler.
Bluefin migration patterns may have shifted as well with the emergence of a dead zone in the Gulf of Mexico that tuna use for spawning. It is suspected that silt from the Mississippi River is responsible for filling in the area south of New Orleans and lowering oxygen levels, rendering it unable to support the life it previously could.
Spawning in different locations would likely change historic data and patterns, the UNH study noted.