Many people have heard of bluefin tuna, even if they haven't eaten it. Bluefin, which are among the world's most remarkable animals, can reach 1,500 pounds, migrate across the Atlantic, dive to depths of more than 3,000 feet and swim at breakneck speeds. They have also been pursued for centuries for their rich, buttery flesh. Traditional bluefin fisheries used to be sustainable, but loosely regulated industrial-scale fishing changed everything for this amazing fish.
Atlantic bluefin are managed as two separate populations, based on where they reproduce. In the western Atlantic, they spawn in the Gulf of Mexico. In the east, they spawn in the Mediterranean Sea. Although these fish crisscross the ocean, each stock returns annually to breed in its place of origin.
The western population of mature Atlantic bluefin has dropped 82 percent since 1970; only about 41,000 tuna that are able to reproduce remain. As early as 1982, scientists and fisheries managers recognized the importance of protecting severely depleted bluefin in the Gulf of Mexico and prohibited targeted fishing for this species.
However, a loophole remains. Surface longline fishermen targeting yellowfin tuna and swordfish are permitted to keep up to three bluefin per trip if they are caught incidentally. From January through June, as bluefin return to the Gulf to breed, surface longline fishermen land hundreds of these giant fish. About a quarter are kept for sale, and the remainder, mostly dead, are thrown overboard. According to U.S. data, surface longlines in the Gulf of Mexico kill more fish now than thirty years ago.
Problems with Surface longlines
In the Gulf of Mexico, surface longlines stretch on average for 30 miles and dangle approximately 800 baited hooks. These hooks, left unattended sometimes for up to 18 hours, routinely catch more than 80 different animals, including protected species such as bluefin tuna, blue marlin, sailfish and endangered loggerhead sea turtles. Surface longlines also harm an inordinate amount of the targeted species because of size restrictions. Fishermen discard approximately half of all swordfish caught, and 77 percent of those discards are dead.
The United States has tried for years to reduce dead discards from surface longlines, including establishing closed areas to this fishing method in the Atlantic and part of the Gulf of Mexico, prohibiting the use of live bait and regulating hook shape, size and strength. Yet these fishermen still harm vulnerable ocean wildlife. The good news is that long-term solutions to this decades-old problem are available. Two relatively new types of fishing gear might finally solve the issue of catching and killing non-targeted animals while keeping Gulf fishermen on the water, so they can continue to provide yellowfin tuna and swordfish to market.
Buoy gear, developed on Florida's east coast, is an effective way to catch swordfish in an area closed to surface longlines. This fishing method involves approximately 15 pieces of gear, including two or three buoys and a main line attached to a baited hook that drifts with the current. The fishermen stay with the gear and pull swordfish in by hand. Onboard research indicates extremely low rates of unintended catch, and almost all undersize swordfish are released alive because the fishermen actively watch for bites and quickly release "short" fish.
Green stick gear is a trolling method developed by the Japanese that is now used off the mid-Atlantic coast. Using a fiberglass pole, boats drag a line that is kept taut by a weight. From the line dangle four to 10 hooks that dip in and out of the water, mimicking a school of flying fish chased by a predator. This gear has proved to be effective at catching yellowfin tuna. Moreover, because catches are brought back to the boat in minutes, discarded fish stand a much greater chance of survival compared with those caught on surface longlines.
These two gears will not only reduce the amount of bluefin tuna caught and killed by surface longlines in the Gulf of Mexico, but they also could reduce unnecessary deaths of countless other ocean animals that come into contact with this indiscriminate fishing gear. If the United States is serious about leading the way toward sustainable management of bluefin tuna, the Gulf of Mexico is the right place to start.
Next time, I'll discuss how fraud and illegal fishing pose two of the biggest problems threatening bluefin in the Mediterranean Sea and continue to keep the number killed well above the legal quota. In mid-November, member countries of the International Commission for the Conservation of Atlantic Tunas will convene to go over these challenges facing bluefin and more. I'll also touch upon this meeting in coming weeks, so stay tuned.