Longline fishing uses thousands of baited hooks to catch fish across the open ocean.

Gardening · Published 3 October 2026 Swipe more like this →

In short: Longline fishing is a massive commercial operation that deploys miles of line and thousands of hooks to target species like tuna and swordfish. While efficient, this technique is notorious for its incidental bycatch, claiming the lives of seabirds, sea turtles, and sharks, sparking intense debate over its environmental impact.

Longline fishing operates by trailing a main line through the water, studded with baited hooks attached via short branch lines known as snoods. Depending on the target species, these lines are set either near the surface to catch pelagic fish like swordfish or along the sea floor to harvest groundfish such as halibut or sablefish. In robust fisheries, such as those in the Bering Sea, a single series of connected lines can span many miles and carry over 2,500 hand-baited hooks.

The primary controversy surrounding the practice is bycatch—the accidental capture of non-target species. Seabirds, particularly albatrosses, are highly vulnerable; an estimated 8,000 are killed annually after becoming hooked while feeding on bait. Efforts to mitigate this mortality include using weighted lines to ensure rapid sinking, deploying bird-scaring streamer lines, and restricting fishing to nighttime. In Hawaii, gear modifications like large circle-hooks have successfully reduced sea turtle bycatch, though the fishery remains subject to strict, litigated limits.

Beyond biological impact, longlining contributes to marine pollution. Fishing equipment, including longlines, is a significant source of oceanic macroplastic and sheds microplastics during operation. Research from the University of Plymouth suggests that older lines are particularly problematic, with 10-year-old gear shedding 760 microplastic fragments per yard towed. Estimates indicate that fishing vessels collectively release between 326 million and 17 billion microplastic fragments into the ocean annually. Furthermore, the work itself is hazardous; a U.S. study found that employees in this sector face injury risks three times higher than the average worker.

Management of these fisheries varies globally. While the Hawaii-based tuna fishery is recognized by the UN Code of Responsible Fishing as well-managed, it still faces criticism for its impact on depleted bigeye tuna stocks and protected wildlife. The complexity of monitoring international waters means that the true scale of bycatch by unregulated vessels remains unknown, leaving the long-term sustainability of the practice a subject of ongoing global concern.

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