Longlining
Discipline · Last reviewed 2026-08-10
A very long mainline carrying thousands of baited hooks on short droppers — highly selective for its target, and the gear most associated with seabird and shark bycatch.
A longline is the industrial extension of a hook and line: a mainline that may run for tens of kilometres, carrying thousands of baited hooks on short snoods, set either on the bottom for demersal species or suspended below floats for pelagic ones.
It is genuinely selective in one dimension and genuinely problematic in another. Hook size and bait choice select strongly for the target species and size, the catch comes aboard individually and in good condition, and there is no seabed contact for pelagic gear. But baited hooks at the surface during setting attract seabirds, which are hooked and drowned; and pelagic longlines fishing for tuna and swordfish take sharks, turtles and billfish as bycatch.
The mitigation story here is unusually clear and worth knowing, because it is one of the strongest examples in fisheries of a bycatch problem being substantially solved by gear measures: bird-scaring streamer lines, line weighting to sink hooks quickly, and night setting have together produced very large reductions in seabird mortality in fisheries that adopted them.
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- Other fishing
- Coverage
- Explained for context and understanding, not taught
FishingHQ covers this method for what it is, how it works, where it came from and what it costs the environment. It does not teach it. Some of these methods are restricted or prohibited in most jurisdictions, and for the commercial ones the useful content is the mechanism and the impact rather than instruction.
What it is
Commercial fishing with a long mainline carrying large numbers of baited hooks on short branch lines. Demersal longlines are anchored on the bottom; pelagic longlines are suspended from surface floats and drift.
How it works
The line is set from the vessel with hooks baited and attached as it runs out, left to fish for a period, and then hauled with the catch removed hook by hook. Selectivity comes from hook size and shape, bait type, and the depth at which the line is set — circle hooks in particular reduce deep hooking and improve the survival of released bycatch.
Equipment
Mainline, snoods, hooks, floats or anchors, a line hauler, and — where properly equipped — bycatch mitigation gear: bird-scaring streamer lines, line weighting, and setting chutes that put hooks below the surface quickly.
Modern use
Longlining is used worldwide for tuna, swordfish, cod, ling, hake, halibut and many other species. Mitigation measures are mandatory in a number of fisheries and management areas, and compliance rather than availability is generally the limiting factor.
Where there is disagreement
Seabird bycatch, particularly of albatrosses and petrels, was a major driver of population decline in several species. That is the clearest case in modern fisheries of a technical fix working: streamer lines, weighted lines and night setting reduce seabird mortality dramatically where they are used. Shark and turtle bycatch on pelagic gear remains a larger and less resolved problem.
Where to go next
Where it is practised
- Greenland and the high ArcticLonglining for Greenland halibut is worked from small boats in summer and through the sea ice in winter, and is a substantial small-scale commercial fishery.
- The Humboldt CurrentLonglining takes the larger demersal and pelagic species of the system alongside the small pelagic fishery.
- The Strait of GibraltarLonglining takes swordfish and large pelagics in the deeper water either side of the sill, from both coasts.
- The Strait of MessinaLonglining takes the bulk of the modern swordfish catch regionally, and is neither as selective as harpooning nor as indiscriminate as the driftnets it replaced.
What these connections rest on (4)
Practitioner consensus — 4 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Greenland and the high Arctic
A discipline that is characteristic of the place rather than merely possible there, joined so a reader can move between the place and the practice.
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practice associating this discipline with this place, recorded as practitioner consensus rather than as tested fact.Background and mechanism onlyCitation checked — the work exists and is described correctly
- Fishers' Craft and Lettered Art: Tracts on Fishing from the End of the Middle Ages — University of Toronto Press, 1997 (Scientific literature)Relied on for: That fishing traditions develop around the water and quarry available to them, and the historical method of reading such traditions.States this directlyCitation checked — the work exists and is described correctly
The Humboldt Current
A discipline that is characteristic of the place rather than merely possible there, joined so a reader can move between the place and the practice.
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practice associating this discipline with this place, recorded as practitioner consensus rather than as tested fact.Background and mechanism onlyCitation checked — the work exists and is described correctly
- Fishers' Craft and Lettered Art: Tracts on Fishing from the End of the Middle Ages — University of Toronto Press, 1997 (Scientific literature)Relied on for: That fishing traditions develop around the water and quarry available to them, and the historical method of reading such traditions.States this directlyCitation checked — the work exists and is described correctly
The Strait of Gibraltar
A discipline that is characteristic of the place rather than merely possible there, joined so a reader can move between the place and the practice.
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practice associating this discipline with this place, recorded as practitioner consensus rather than as tested fact.Background and mechanism onlyCitation checked — the work exists and is described correctly
- Fishers' Craft and Lettered Art: Tracts on Fishing from the End of the Middle Ages — University of Toronto Press, 1997 (Scientific literature)Relied on for: That fishing traditions develop around the water and quarry available to them, and the historical method of reading such traditions.States this directlyCitation checked — the work exists and is described correctly
The Strait of Messina
A discipline that is characteristic of the place rather than merely possible there, joined so a reader can move between the place and the practice.
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practice associating this discipline with this place, recorded as practitioner consensus rather than as tested fact.Background and mechanism onlyCitation checked — the work exists and is described correctly
- Fishers' Craft and Lettered Art: Tracts on Fishing from the End of the Middle Ages — University of Toronto Press, 1997 (Scientific literature)Relied on for: That fishing traditions develop around the water and quarry available to them, and the historical method of reading such traditions.States this directlyCitation checked — the work exists and is described correctly
Compared with
- Purse seiningBoth target the same pelagic stocks and fail differently. A longline is selective by hook, bait and depth but hooks seabirds, turtles and sharks on the surface; a purse seine takes a whole school at once, including everything travelling with it.
- TrawlingBoth are large-scale commercial methods and their environmental profiles differ in kind rather than in degree: one is a bycatch and hooking problem, the other a seabed and selectivity one.
What these connections rest on (2)
Authoritative guidance — 2 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Purse seining
A comparison of failure modes rather than of virtue, held to an authoritative standard because both claims are about documented bycatch patterns.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: The classification of longline and purse seine gear and the bycatch characteristics associated with each.States this directlyCitation checked — the work exists and is described correctly
- ICES Advice on fishing opportunities, catch and effort — International Council for the Exploration of the Sea (Scientific institute)Relied on for: That gear-specific bycatch is assessed as part of the scientific advice underlying fisheries management.Background and mechanism onlyCitation checked — the work exists and is described correctly
Trawling
International fisheries description of both gear types.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Descriptions of longline and trawl gear and their operation.States this directlyCitation checked — the work exists and is described correctly
Environment and conservation
- Bycatch and discardsThe seabird case is the clearest example available of a fisheries bycatch problem substantially solved by changing the gear.
- Fish stocks and sustainabilityLonglining takes large predatory species with slow life histories, which is the combination that makes stock recovery slow once pressure is applied.
What these connections rest on (2)
Authoritative guidance — 2 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Bycatch and discards
Seabird and shark bycatch in longline fisheries, and the mitigation measures addressing them, are documented.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Longline bycatch and the mitigation measures — streamer lines, weighting, night setting — used to reduce it.States this directlyCitation checked — the work exists and is described correctly
Fish stocks and sustainability
Scientific advice and conservation assessment of affected stocks.
- ICES Advice on fishing opportunities, catch and effort — International Council for the Exploration of the Sea (Scientific institute)Relied on for: Advice on fishing pressure and the state of exploited stocks.States this directlyCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: Assessment of stock status by gear type and fishery.Background and mechanism onlyCitation checked — the work exists and is described correctly
History and culture
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Handline and dropline traditions
A record joined to the history behind it. Historical placement rests on the documentary and scholarly sources cited; where the tradition is living rather than documented, the claim is kept at the level those sources support.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Classification and description of world fishing gears, including traps, weirs, handlines, droplines and longlines.States this directlyCitation checked — the work exists and is described correctly
- Fishers' Craft and Lettered Art: Tracts on Fishing from the End of the Middle Ages — University of Toronto Press, 1997 (Scientific literature)Relied on for: Historical fishing gear, its organisation and the legal and economic context in which it was used.States this directlyCitation checked — the work exists and is described correctly
Check the rules before you fish
Fishing laws, bylaws, access rules, seasons, bait restrictions and permitted methods vary by location and can change. Check the current rules from the relevant authority and the water you intend to fish before fishing.
Check with:
- Current national or regional law for where you are fishing
- Current local bylaws
- The relevant fisheries authority
- The landowner, club or fishery whose water it is
- Any restrictions specific to the species or the method you intend to use
Sources for this page
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: The mechanics of demersal and pelagic longlines, and the mitigation measures used to reduce seabird bycatch.States this directlyCitation checked — the work exists and is described correctly
- ICES Advice on fishing opportunities, catch and effort — International Council for the Exploration of the Sea (Scientific institute)Relied on for: That longline fisheries are managed with technical measures addressing bycatch alongside catch limits.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.