Longline Fishing

Longline fishing, or longlining, is a commercial fishing angling technique that uses a long main line with baited hooks attached at intervals via short branch lines called snoods or gangions. A snood is attached to the main line using a clip or swivel, with the hook at the other end. Longlines are classified mainly by where they are placed in the water column. This can be at the surface or at the bottom. Lines can also be set by means of an anchor or left to drift. Hundreds or even thousands of baited hooks can hang from a single line. Longliners – fishing vessels rigged for longlining – commonly target swordfish, tuna, halibut, sablefish, and many other species.

Guideline

In some unstable fisheries, such as the Patagonian toothfish, fishermen may be limited to as few as 25 hooks per line. In contrast, commercial longliners in certain robust fisheries of the Bering Sea and North Pacific generally run over 2,500 hand-baited hooks on a single series of connected lines many miles in length. Longlines can be set to hang near the surface to catch fish such as tuna and swordfish or along the sea floor for groundfish such as halibut or cod. Longliners fishing for sablefish, also referred to as black cod, occasionally set gear on the sea floor at depths exceeding 1100 meters using relatively simple equipment. Longlines with traps attached rather than hooks can be used for crab fishing in deep waters.

Terminology

In Hawaii, where Japanese immigrants introduced longlining in 1917, longline fishing was known as flagline fishing because of the use of flags to mark floats from which hooks were suspended. The term "flagline fishing" persisted until local fishing vessels began to use modern monofilament mainlines, line setters, and large, hydraulically powered reels when the term "longline fishing" was adopted. Longline fishing is prone to the incidental catching and killing of dolphins, seabirds, sea turtles, and sharks, but less so than deep-sea trawling.

Incidental Catch

Longline fishing is controversial because of bycatch, fish caught while seeking another species, or immature juveniles of the target species. This can cause many issues, such as the killing of many other marine animals while seeking certain commercial fish. Seabirds can be particularly vulnerable during the setting of the line. Methods to mitigate incidental mortality have succeeded in some fisheries. Mitigation techniques include the use of weights to ensure the lines sink quickly, the deployment of streamer lines to scare away birds, setting lines only at night in low light, limiting fishing seasons to the southern winter, and not discharging offal while setting lines.

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