Ocean activists seem to be on the eve of winning a long battle against a controversial type of fishing gear that has been banned in most of world's oceans. But many fishermen are not ready to let go of what has been a reliable method for catching valuable swordfish.

A federal court ruling last week could lead to strict limits on using drift gillnets in California, one of the last places where the gear is still allowed. Drift gillnets are used to snag swordfish but prone to ensnaring other sea life, too. The court decision comes weeks after the state's governor signed a law that would phase the nets out of use over the next few years.

Todd Steiner, an environmentalist who has fought for stricter regulations on drift gillnets since the 1990s, believes the time has come to ban them everywhere.

"Drift gillnets should no longer be in the ocean," says Steiner, founder of the based in Forest Knolls, Calif. "Only one in six or seven animals caught in these nets is a swordfish. They're indiscriminate in what they catch."

Drift gillnets are essentially long curtains of nearly invisible mesh that hang from buoys and entangle large creatures that swim into them. The nets are notorious for catching high volumes of unwanted creatures, or bycatch — the primary reason Steiner and other activists want them banned.

But Santa Barbara fisherman Gary Burke, who has been using drift gillnets since the 1980s, says environmentalists who oppose the gear have set unrealistic expectations. "We've reduced our bycatch so much at this point that it would take some dramatic tech innovation to reduce it anymore," he says.

Since the late 1990s, federal law has required that drift gillnets be equipped with sonic "pingers" that alert dolphins to the lethal barriers and that the nets be set with a 36-foot open space at the surface for turtles, birds and marine mammals to slip through safely. These changes have helped reduce, though not eliminate, bycatch.

Activists say it's not enough. "Despite various measures to reduce bycatch, the California drift gillnet swordfish fishery remains one of the dirtiest and most indiscriminate fisheries in the country, discarding over half of all the fish they catch, including ecologically important large sharks and valuable sportfish like marlins," says Geoff Shester, the California campaign director for the group Oceana.

While gillnets are used to catch herring, salmon and halibut in parts of the United States, the mesh size used to catch such fish is small enough that the nets tend to deflect, rather than entangle, marine mammals and turtles. Gillnets set for swordfish, though, have a mesh diameter well over one foot, which allows large animals to become tangled, often around their necks.

Around the world, ocean activists have successfully made the case that using drift gillnets for swordfish is unsustainable. This has led to bans in the Mediterranean, in Russia and throughout international waters. Among U.S. states, only California still allows the nets. Here, about 20 boats deploy the gear in offshore waters to catch not only swordfish but also thresher sharks and opah. The nets may be a mile in length and 200 feet top to bottom.

But the days may be numbered for the small fishery. In late September, California Gov. Jerry Brown signed into law Senate Bill 1017, which mandates that drift gill nets be phased out of use over a four-year period. The government must come up with $2 million to buy out the fishermen —money that must still be found.

California's drift gill net fishery is also the target of federal legislation sponsored by California Democrat Sen. Dianne Feinstein that would do essentially the same thing as the new state law.

And, Oceana won a key lawsuit against the U.S. National Marine Fisheries Service and the Department of Commerce in late October which could shut down the fishery. The ruling, handed down Oct. 24 in a federal court in Los Angeles, found the federal agency's removal of strict limits on bycatch in 2017 to be illegal because that action was taken without public input. The court ruling calls for bycatch limits, called "hard caps," that will force California fishermen using drift gillnets to reel in their gear for the season, or longer, if they accidentally catch and kill too many whales, dolphins or other protected species.

"Ultimately, this is an incentive for the drift gillnet fleet to shift away from this gear and phase it out," Oceana's Shester says.

Proponents of the fishery, though, say the impacts are being exaggerated. Michael Milstein, a public affairs officer with the National Oceanic and Atmospheric Administration, says the Endangered Species Act as well as the Marine Mammal Protection Act already impose strict protections for imperiled species _— protections Milstein says are working well.

"Bycatch has gone way down since the 1990s," he says.

This is partly because there are far fewer boats using drift gillnets now, down from 141 off the California coast in 1990 to 17 in 2017. However, a 2017 fishery analysis produced in part by National Marine Fisheries Service shows that the rate of bycatch per net has also declined.

Drift gillnets are not the only gear that can catch swordfish. Some fishermen use harpoons, for example, and a handful of California fishermen are testing out a new system called deep-set buoy gear. Consisting of baited hooks deployed rapidly to 1,000 feet or more underwater, where swordfish hang out during daylight hours, deep-set buoy gear is very unlikely to catch air-breathing mammals, birds and turtles.

"We studied the movement patterns of swordfish to help us design gear that targets the fish when they're physically segregated from species that we don't want to catch," explains scientist Chugey Sepulveda, who has worked with commercial fishermen to innovate and design the new system. Sepulveda, the director of the Pfleger Institute of Environmental Research, says that in 1,200 days of test fishing he has accidentally caught – and successfully set free – only two elephant seals.

But Burke says he knows other fishermen who are using deep-set buoy gear and finding it difficult to catch swordfish.

"In 50 sets [of the gear], they've caught six fish," he says, adding that the catch must be sold for two times the price of gillnetted swordfish to offset the reduced production.

Burke says drift gillnets are the only economically viable way to catch affordable swordfish and that banning them in California will cause more harm than good by generating more demand for imported swordfish. He says foreign fleets catch swordfish using nets and longlines and with fewer regulations than those governing the California fishery.

"The idea is to reduce imports of seafood," he says. "We're doing the exact wrong thing here by talking about a ban."

But where Burke sees economic hurdles and unnecessary hardships for fishermen, Shester sees progress.

"It's taken a long time, but we're shifting in the right direction," Shester says. "By signing the state legislation, the governor has said it's time to move on."

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