Is There Light at the End of the Tunnel for Bluefin Tuna?

Majestic Bluefin tuna migrate thousands of miles from the Atlantic Ocean to the Gulf of Mexico to breed and can grow up to 1,500 pounds during their relatively long lives. But only a small number get the chance to reach maturity.

Although it has been illegal to intentionally fish for Bluefin tuna in the Gulf of Mexico for decades, they are still caught in significant numbers by commercial fisherman, said Tom Wheatley, an environmental advocate with the Pew Charitable Trusts.

That's largely due to the use of longlines, a commercial fishing technique that uses long fishing lines that stretch for up to 30 miles across the surface of Gulf waters, towed behind ships, and holding up to 750 hooks.

Though these longlines are intended to catch yellowfin tuna and swordfish, they end up hooking and killing up to 80 different unintended species—called bycatch—such as sea turtles, marine mammals and Bluefin tuna, Wheatley said.

But there may be a "light at the end of the tunnel," according to Wheatley.

The National Marine Fisheries Service, which sets rules for fishermen in American waters, is considering a new rule to limit the use of longlines in the Gulf, the only spawning ground for the western stock of Atlantic Bluefin (which, like other populations of Bluefin worldwide, have been "overfished for decades," he said).

Although the rule isn't expected until this summer, a draft version presented last fall suggested that longline fishing could be prohibited in the Gulf, at least at certain times and in specific areas.

At the same time, researchers—collaborating with commercial fishermen—have shown that two new types of fishing gear can be used to catch yellowfin and swordfish while snaring far less unintended bycatch, said Wheatley, who's the manager of Pew's Gulf surface longline campaign.

The first method targets swordfish. Used only at night, when swordfish are active, the system consists of a line of about 15 buoys, each outfitted with a hook and often illuminated. If a fish hits one of the hooks, the buoy moves out of line, and the fisherman pulls it in to see what he's caught.

This allows fishermen to set free fish that aren't targeted, or aren't big enough to legally hold. That stands in stark contract to longlines, which are often let out as long as 18 hours. During this time, the hooks can drown animals like sea turtles and Bluefin tuna, which need to swim to breathe, and fight themselves to the bring of death after being hooked, Wheatley said.

The second promising method is called greenstick gear and targets yellowfin tuna, using a short line of squid-like bait. At the end of this is a fish-shaped weight, which keeps the line taught and makes the whole assemblage look like a fish chasing a group of prey. The lures, set just at the surface or slightly above, mimic squid or flying fish, some of the yellowfin's favorite foods. It's designed to appeal to yellowfin, and is brought in often to collect hooked fish, Wheatley said.

These methods are being tested by two commercial vessels in the Gulf, in a research program initiated by David Kerstetter, a researcher at Nova Southeastern University.

So far, these techniques have caught far fewer unintended animals than longlines. More than 90 percent of the tuna caught using the greenstick gear were yellowfin or other tuna species, not including Bluefin tuna, according to Pew. The fishermen have also caught zero sea turtles or marine mammals, and are able to remove unintentionally-hooked Bluefin before they die, Wheatley added.

Wheatley thinks this could help improve the health of the ecosystem, as well as that of the local economy, by providing more jobs. The quality of fish caught is likely to be higher, he said, since fewer fish are killed as the hooks are pulled in almost immediately. (With longlines, for example, about half the swordfish caught are discarded because they are dead by the time they are pulled in, and thus worthless, he said.)

These types of gear also require less gasoline. A typical longline fishing trip uses up about $10,000 to $12,000 worth of fuel. A trip in a smaller vessel would use much less, he said.

Bluefin losses from longlines were exacerbated by the BP Deepwater Horizon oil spill on April 20, 2010, right at the peak of Bluefin tuna spawning season. He thinks that some of the money paid out by BP ought to be used to help provide Gulf fishermen with some of these new types of fishing gear.

The National Oceanographic and Atmospheric Administration, which runs the fisheries service, has enough money to begin doing this now, although more funds could be allotted from BP in the future. "They could do it now," he said.

After the proposed rule comes out, there will be a short comment period to petition NOAA to outlaw longline fishing in the Gulf.

"I think there's a good possibility for all of this to happen, " Wheatley said. "We’ve been putting together a strong case that there's a win-win possibility—good for the fishermen and the fish. That's a pretty amazing thing that doesn't happen with many environmental issues every day."

Related stories on TakePart:

• A Tuna Turnaround? Bluefin Populations Are On The Rise

• Jellyfish Invasion: A Stinging Reminder of Overfishing and Climate Change

• Bluefin Tuna Population ‘Probably Okay’ After BP Oil Spill

Douglas Main is a science and environmental journalist. He's currently a staff writer for LiveScience.com and has written for such venues as the New York Times Green Blog, Popular Mechanics and Discover Magazine. He got an M.A. in journalism from New York University and lives in New York City.  TakePart.com