Longline fishing, or longlining, is a

commercial fishing Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...

angling Angling is a fishing technique that uses a fish hook or "angle" (from Old English ''angol'') attached to a fishing line to tether individual fish in the mouth. The fishing line is usually manipulated via a fishing rod, although rodless techni ...

technique that uses a long ''main line'' with baited

hook A hook is a tool consisting of a length of material, typically metal, that contains a portion that is curved or indented, such that it can be used to grab onto, connect, or otherwise attach itself onto another object. In a number of uses, one e ...

s attached at intervals via short branch lines called ''snoods'' or ''gangions''.Method and Apparatus for Long Line and Recreational Bait Fishing
Patent application 20080202013. 28 August 2008. 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 A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

. 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. This can lead to many deaths of different marine species (see bycatch). Longliners –

fishing vessel A fishing vessel is a boat or ship used to catch fish in the sea, or on a lake or river. Many different kinds of vessels are used in commercial, artisanal and recreational fishing. The total number of fishing vessels in the world in 2016 was ...

s rigged for longlining – commonly target swordfish,

tuna A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max len ...

halibut Halibut is the common name for three flatfish in the genera '' Hippoglossus'' and '' Reinhardtius'' from the family of right-eye flounders and, in some regions, and less commonly, other species of large flatfish. The word is derived from ''h ...

sablefish The sablefish (''Anoplopoma fimbria'') is one of two members of the fish family Anoplopomatidae and the only species in the genus ''Anoplopoma''. In English, common names for it include sable (US), butterfish (US), black cod (US, UK, Canada), b ...

and many other species. In some unstable fisheries, such as the

Patagonian toothfish The Patagonian toothfish (''Dissostichus eleginoides'') is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around most ...

, 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 The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

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 (

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

longline) to catch fish such as tuna and swordfish or along the sea floor ( demersal longline) for groundfish such as halibut or

cod Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not call ...

. Longliners fishing for

, also referred to as black cod, occasionally set gear on the sea floor at depths exceeding using relatively simple equipment. Longlines with traps attached rather than hooks can be used for

crab fishing Crab fisheries are fisheries which capture or farm crabs. True crabs make up 20% of all crustaceans caught and farmed worldwide, with about 1.4 million tonnes being consumed annually. The horse crab, '' Portunus trituberculatus'', accounts for o ...

in deep waters. Longline fishing is prone to the

incidental catch In fishing, incidental catch is that part of the catch which was not originally targeted, but was caught and retained anyway. It can be contrasted with discards, which is that part of the catch which was not originally targeted, but was caught and ...

ing and killing of

dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhe ...

s, and

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...

s, but less so than deep sea

trawling Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different spec ...

. In

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

, 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 mainline, line setters, and large, hydraulically powered reels, when the term "longline fishing" was adopted.

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 (to avoid attracting birds), limiting fishing seasons to the southern winter (when most seabirds are not feeding young), and not discharging

offal Offal (), also called variety meats, pluck or organ meats, is the organs of a butchered animal. The word does not refer to a particular list of edible organs, which varies by culture and region, but usually excludes muscle. Offal may also refe ...

while setting lines. The Hawaii-based longline fishery for swordfish was closed in 2000 over concerns of excessive sea turtle by-catch, particularly

loggerhead sea turtle The loggerhead sea turtle (''Caretta caretta'') is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around in carapace length when fully ...

s and

leatherback turtles The leatherback sea turtle (''Dermochelys coriacea''), sometimes called the lute turtle or leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to and weights ...

. Changes to the management rules allowed the fishery to reopen in 2004. Gear modification, particularly a change to large circle-hooks and mackerel-type baits, eliminated much of the sea turtle by-catch associated with the fishing technique. It has been claimed that one consequence of the closure was that 70 Hawaii-based vessels were replaced by 1,500-1,700 longline vessels from various Asian nations, but this is not based on any reliable data . Due to poor and often non-existent catch documentation by these vessels, the number of sea turtles and albatross caught by these vessels between 2000 and 2004 will never be known . Hawaii longline fishing for swordfish closed again on 17 March 2006, when the by-catch limit of 17 loggerhead turtles was reached. In 2010 the by-catch limit for loggerhead turtles was raised, but was restored to the former limit as a result of litigation. The Hawaii-based longline fisheries for tuna and swordfish are managed under sets of slightly different rules. The tuna fishery is one of the best managed fisheries in the world, according to the UN Code of Responsible Fishing, but has been criticized by others, as being responsible for continuing by-catch of

false killer whale The false killer whale (''Pseudorca crassidens'') is a species of oceanic dolphin that is the only extant representative of the genus '' Pseudorca''. It is found in oceans worldwide but mainly in tropical regions. It was first described in 184 ...

s, seabirds, and other nontargeted wildlife, as well as placing pressure on depleted

bigeye tuna The bigeye tuna (''Thunnus obesus'') is a species of true tuna of the genus '' Thunnus'', belonging to the wider mackerel family Scombridae. In Hawaiian, it is one of two species known as ahi, the other being the yellowfin tuna. Bigeye tuna are ...

stocks. Commercial longline fishing is also one of the main threats to albatrosses. Of the 22 albatross species recognized in the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

, six are threatened, and nine are vulnerable. The IUCN lists three species as critically

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...

: the Amsterdam albatross, the

Tristan albatross The Tristan albatross (''Diomedea dabbenena'') is a large seabird from the albatross family. One of the great albatrosses of the genus ''Diomedea'', it was only widely recognised as a full species in 1998. Taxonomy Albatrosses belong to the fami ...

and the

waved albatross The waved albatross (''Phoebastria irrorata''), also known as Galapagos albatross,Remsen Jr., J.V. (2008) is the only member of the family Diomedeidae located in the tropics. When they forage, they follow a straight path to a single site off the ...

. The remaining four are near threatened. Albatrosses and other

s which readily feed on

are attracted to the set bait, become hooked on the lines and drown. An estimated 8,000 albatross per year are killed in this way. A simple device which can be fitted onto longlines, known a
Hookpod
has been proposed for mitigation of seabird bycatch; Hookpod was rolled out to a total of 15 commercial fishing vessels in New Zealand after a change in regulations in January 2020, with a result of zero seabird bycatch in the first 6 months.

Microplastics

Oceanic

microplastics Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...

pollution is largely caused by plastic-made fishing gear like longline fishing equipment or drift nets, that are wearing down by use, lost or thrown away.

Safety

In the US, a study found that the risk for non-fatal injuries was 35 per 1,000

full-time equivalent Full-time equivalent (FTE), or whole time equivalent (WTE), is a unit that indicates the workload of an employed person (or student) in a way that makes workloads or class loads comparable across various contexts. FTE is often used to measure a ...

employees, about three times higher than average U.S. worker. (This is compared to 43 per 1,000 in the trawler fleet).

Historic images

Notes

References

* * Brothers, N P; Cooper, J and Lokkeborg S (1999) ''The Incidental catch of seabirds by longline fisheries''. Rome,

FAO The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...

Fisheries Circular No 937. * Eigaard B, Thomsen H, Hovgaard H, Nielsen A and Rijnsdorpd AD (2011
"Fishing power increases from technological development in the Faroe Islands longline fishery"
''Canadian Journal of Fisheries and Aquatic Sciences'', 69 (11): 1970–1982. * FAO (2009) ''Technical Guidelines for Responsible Fisheries, Number 1: Fishing operations, supplement
Best practices to reduce incidental catch of seabirds in capture fisheries
Rome. . * * George JP (1993
''Longline fishing''
Volume 22 of FAO Training Series, FAO, Rome. . * Jhonson, Duglas H; Shaffaz, Terry Lickmadik and Gould, Penistrick J (1990

U.S. Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and ...

. * Valdemarsen, John

UN Atlas of the Oceans: Fishery Technology Service.
Set longlines
''FAO Fishing Gear Types'', Rome. Retrieved 24 March 2012.
Industrial Tuna Longlining
''FAO Fishing Techniques'', Rome. Retrieved 24 March 2012. * Pham, Christopher K; Diogo, Hugo; Menezes, Gui; et al
Deep-water longline fishing has reduced impact on Vulnerable Marine Ecosystems
Scientific Reports, via Nature Magazine online. Retrieved 30 December 2015.

External links

Longlining
''Seafood Watch'', Fishing Methods Fact Card. Retrieved 23 January 2012.

''New Zealand Seafood Industry Council''.
Talleres Hermida S.L
''Pioneer in manufacture of surface paternoster line and systems longline''. {{Authority control Fishing industry Fishing techniques and methods