December 5, 2023

Novelties: Fish Hooks Designed to Avoid the Wrong Catch

Starting this month, commercial fishing vessels that drop long lines in the Gulf of Mexico in search of tuna are mandated to use lightweight circular hooks that retain approved fish like yellowfin tuna, but flatten under the weight of the far heavier bluefin and allow them to swim free.

Bluefin populations have declined precipitously, and bluefin fishing is prohibited in the gulf. But the bluefin, which spawn there, are sometimes snared accidentally by long-line fishermen. Tuna fishing vessels are allowed to retain some bluefin caught accidentally, depending on the pounds of the intended catch on board. The new “weak” hook, as it is known, is aimed at reducing this unintended catch, said John Mitchell, who helped develop it. He is a unit leader in Pascagoula, Miss., at the Southeast Fisheries Science Center of the National Oceanic and Atmospheric Administration.

Hook design alone won’t save the world’s endangered sea creatures, said John E. Graves, a professor of marine science at the Virginia Institute of Marine Science in Gloucester Point, Va., but he added that the new product is a good idea. Dr. Graves’s work at the institute, which is part of the College of William Mary in Williamsburg, Va., includes research on ways to reduce incidental catching of fish by long lines.

“It’s not a magic bullet,” he said of the new hook, but he observed that “it turns out that the hook type you use can have a huge impact on survival.”

One of the businesses that worked with NOAA on the weak hooks was Mustad of Norway, said Steve Tagami, a sales director at the company. Its hooks are now sold at various locations.  

Mr. Mitchell said that in two years of tests in the gulf with commercial fishermen, the new hooks reduced the number of accidentally caught bluefins by 56 percent, without reducing the catch of targeted fish like yellowfin. The circular hook is similar to a slightly heavier one already in use to reduce the number of sea turtles caught on long lines.

Mike Carden, captain of the 80-foot Daytona in Panama City, Fla., helped to test the new hooks. The lines, which extend for miles and hold hundreds of hooks, go out in the morning in a process that takes about five hours, and are then pulled in again at night. Using the new hooks, he said, “we didn’t catch stuff we didn’t want, like bluefin, turtles and big marlins.”

The circular hook tends to dig in less deeply than a regular, J-shaped hook, Dr. Graves said. The new hook often lodges in the jaw instead of, for example, ending up in the esophagus or stomach as J-shaped hooks often do.

In a study of white marlins, Dr. Graves found that fewer than 2 percent died after release from circular hooks, in comparison with 35 percent that were caught on J-hooks. “It’s quite a difference,” he said, “just with a different hook.”

Mr. Mitchell said the next step in preserving bluefin would be research into how long it takes for a bluefin to straighten the hook and escape. He hopes the study will show that the fish accomplish this rapidly, he said, adding that if the hook is straightened only as the line is hauled back, the fish could be subjected to a long, stressful period.

The amount of time that lines stay in the water varies, he said. Some fisheries put the lines out and then double-back to collect them; others let the lines soak for five or six hours before returning for them.

This month, NOAA wants to begin a new study in the gulf, using submersible timers and depth recorders on lines holding the hooks, he said. When flattened hooks are hauled aboard after a day’s fishing, the devices can be examined to see how long the bluefin were on them before swimming free.

RESEARCHERS at the agency have also come up with a hook that monitors fish and assesses their vitality. Dr. M. Elizabeth Clarke, a researcher at the agency’s Northwest Fisheries Science Center in Seattle, along with other team members, devised a spring-loaded hook that lets fish go but preserves a DNA sample. The agency patented the hook in 2010. Dr. Clarke said that the hook grabs a tiny piece of fish tissue and then springs back into a hollow tube, retaining the genetic sample as the fish departs.

“We don’t kill the fish,” she said. “Instead, we get myriad information without having to haul them to the surface.” The information can be used to estimate populations and even, with additional facts, to identify individual fish.

Dr. Clarke conserves fish away from work, too — when she is out in a stream near a family vacation home, enjoying her hobby of fly fishing. “I don’t use a barb,” she said, “and I gently release all the fish I catch.” The technique seems to work.

Occasionally, she said, she spots a familiar-looking fish that she may once have caught and released — swimming by, unscathed.


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