Trawling
Discipline · Last reviewed 2026-08-10
Towing a large net through the water or along the seabed — the dominant commercial fishing method by volume, and the most environmentally contested.
A trawl is a cone of netting towed behind a vessel, held open by boards, beams or by the water flow, and emptied from the closed end. It is the method that catches most of the world's fish by weight, and it is the one whose environmental effects are argued about most.
The mechanics matter for understanding the argument. A pelagic trawl is towed in midwater and touches nothing; a bottom trawl is towed along or just above the seabed and, in the beam trawl form, is designed specifically to disturb the top layer of sediment to lift flatfish out of it. Those are very different gear with very different consequences, and treating them as one thing — which public discussion often does — makes the discussion incoherent.
The recognised issues are seabed disturbance, bycatch and discarding, and fuel intensity. The recognised responses are gear modification, spatial closures, mesh and selectivity rules, and catch quota management. None of these is settled, and FishingHQ presents the evidence and the uncertainty rather than adopting a position.
- Section
- 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 by towing a funnel-shaped net. Pelagic trawls fish in the water column for schooling species; demersal or bottom trawls fish on or near the seabed; beam trawls use a rigid beam and ground gear to work flatfish out of soft sediment.
How it works
The net is held open horizontally by otter boards angled to shear outwards, or by a rigid beam, and vertically by floats on the headline and weights on the footrope. Fish that cannot swim clear of the tow are funnelled back into the cod end, which is where mesh size determines what is retained and what escapes. Selectivity is therefore engineered rather than incidental: mesh size, mesh shape, escape panels and sorting grids are all deliberate design choices, and they are what most gear regulation addresses.
Equipment
A vessel with sufficient towing power, warps, otter boards or a beam, the net itself with headline floats and a footrope, and — on demersal gear — ground gear ranging from light rope to heavy rollers or chain matting. Selectivity devices such as square-mesh panels and separator grids are increasingly standard.
Modern use
Trawling accounts for a large share of global marine capture production. Management is via quota, effort control, spatial closures, and technical measures on gear. Regulation differs substantially by fishery and jurisdiction and changes.
Where there is disagreement
Bottom trawling's effect on seabed habitat is the central dispute, and it is genuinely a dispute: effects vary enormously by habitat type, gear weight and how often ground is worked, with soft mobile sediments recovering far faster than structurally complex biogenic habitats. Bycatch and discarding are the second axis, addressed through selectivity devices and landing obligations with mixed and contested results. FishingHQ's position is that both effects are real and that generalising a single figure across all trawling misrepresents the evidence in either direction.
Where to go next
Where it is practised
- The Indian subcontinent coastsMechanised trawling from the larger ports operates alongside the artisanal sector and is regulated separately from it.
- The West African coastIndustrial trawling operates offshore and, where the inshore exclusion zone is not enforced, inside it, destroying canoe gear as well as taking fish.
What these connections rest on (2)
Practitioner consensus — 2 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.
The Indian subcontinent coasts
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 West African coast
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
- LongliningBoth 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.
- Purse seiningBoth take fish in volume with a net and differ in where: a purse seine encircles a school in the water column, a trawl is towed through or along the bottom.
- Traps and potsThe two ends of the selectivity range. A pot catches what enters it and releases the rest alive when hauled; a trawl catches whatever is in the path of the net. Both are legitimate commercial gear, and the environmental arguments about them are almost entirely arguments about that difference.
What these connections rest on (3)
Authoritative guidance — 3 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Longlining
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
Purse seining
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 purse seine and trawl gear and their operation.States this directlyCitation checked — the work exists and is described correctly
Traps and pots
A gear-selectivity comparison held to an authoritative standard, because it is the basis of most of the public argument about commercial fishing and a loose statement of it would be worse than none.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: The classification of static trap gear and towed net gear, and the selectivity characteristics distinguishing them.States this directlyCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: That gear type is a principal determinant of a fishery's sustainability rating, distinct from the stock status of the target species.States this directlyCitation checked — the work exists and is described correctly
Environment and conservation
- Fish stocks and sustainabilityTrawling's effect on stocks is inseparable from its effect on the seabed those stocks depend on, which is why the two are assessed together rather than as separate questions.
- Bycatch and discardsEverything a fishery catches that it did not intend to — and the area where gear design has produced some of the clearest environmental wins available.
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.
Fish stocks and sustainability
Scientific advice and conservation assessment of trawl fisheries.
- ICES Advice on fishing opportunities, catch and effort — International Council for the Exploration of the Sea (Scientific institute)Relied on for: Advice on demersal stock status and the effects of bottom-contacting gear.States this directlyCitation checked — the work exists and is described correctly
- Cefas science, advice and data on marine and freshwater environments — Centre for Environment, Fisheries and Aquaculture Science (Government fisheries body)Relied on for: Science on seabed habitats and the effects of fishing gear on them.Background and mechanism onlyCitation checked — the work exists and is described correctly
Bycatch and discards
Bycatch and discarding are recognised issues in trawl fisheries and are addressed through gear selectivity measures.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Trawl gear mechanics, selectivity devices and their effect on unwanted catch.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 bycatch is managed through technical measures alongside catch limits.FishingHQ's interpretation of what it saysCitation 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 otter, beam and pelagic trawls and the role of mesh and selectivity devices.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 fishing effects on seabed habitat are assessed by habitat type and gear rather than as a single figure for trawling as a whole.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: That sustainability assessments are made at the level of stock and gear combination.States this directlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.