Purse seining
Discipline · Last reviewed 2026-08-10
Encircling a whole school with a wall of net and drawing the bottom closed like a purse — the principal method for catching pelagic shoaling fish.
A purse seine catches a school rather than individual fish. The vessel runs a wall of netting in a circle around a located shoal, then hauls a line running through rings along the bottom edge, closing the net beneath the fish so they cannot escape downwards. The catch is then concentrated and brought aboard.
It is the method that supplies most of the world's tuna, sardine, anchovy and mackerel, and its environmental profile is a study in how much gear detail matters. A purse seine set on a free-swimming school of tuna is one of the most selective large-scale methods in existence. The same gear set around a fish aggregating device — a floating object that concentrates many species — has a substantially higher bycatch of juveniles and non-target species. Same net, same vessel, very different outcome.
That distinction is why FishingHQ describes gear and its use separately rather than assigning an environmental verdict to a method as a whole.
- 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 in which a long wall of netting is deployed to encircle a school of pelagic fish, and then closed at the bottom by a purse line running through rings, trapping the school.
How it works
A skiff holds one end of the net while the vessel runs a circle around the school. Floats hold the headline at the surface and weights carry the bottom down. The purse line is then hauled, drawing the rings together and closing the bottom of the net into a bag. The net is progressively hauled to concentrate the catch alongside, which is then brought aboard by brailer or pump.
Equipment
A large net with a float line, lead line, rings and a purse line; a power block or net drum for hauling; a skiff; and — critically for how the gear performs — the means of locating fish, which is now sonar, aerial spotting or aggregating devices.
Modern use
Purse seining dominates global landings of small pelagics and tropical tuna. Management combines catch quota, closed seasons and areas, and increasingly rules on the use and design of fish aggregating devices.
Where there is disagreement
The disputed area is not the net but the aggregating device. Setting on free schools produces very low bycatch; setting on aggregating devices raises bycatch of juvenile tuna, sharks and other species substantially, and lost devices contribute to marine debris and to entanglement. Non-entangling and biodegradable device designs are an active response. The evidence that the two set types differ is strong; the right policy response to that is contested.
Where to go next
Where it is practised
- ShetlandThe pelagic fishery operating from the main ports is substantial relative to the islands' population and is central to their economy.
- The Coral TriangleIndustrial purse seining for tuna operates in the region's deep water and is one of the largest tuna fisheries in the world.
- The Humboldt CurrentIndustrial purse seining for anchoveta is the dominant fishery by volume anywhere in the world, operating in short intense openings decided by acoustic survey.
- The Moroccan Atlantic coastThe small pelagic fishery the upwelling supports is worked by purse seine at a scale that makes Morocco one of the world's largest sardine producers.
- The West African coastIndustrial purse seining works the same small pelagic stocks as the canoe fleet, which is the direct source of the region's central fisheries conflict.
What these connections rest on (5)
Practitioner consensus — 5 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.
Shetland
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 Coral Triangle
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 Moroccan Atlantic 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
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 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 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.
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.
Longlining
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 purse seine and trawl gear and their operation.States this directlyCitation checked — the work exists and is described correctly
Environment and conservation
- Bycatch and discardsBycatch here depends on how the gear is SET rather than on the gear itself, which is the point most often lost in public discussion.
- Fish stocks and sustainabilityPurse seining is the dominant gear for the pelagic shoaling species that much of the marine food web depends on, so its management is a food-web question and not only a stock 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.
Bycatch and discards
Free-school and aggregating-device sets differ substantially in bycatch composition.
- FAO fishing gear types and fishing technology information — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: The distinction between free-school and aggregating-device purse seine sets in bycatch terms.States this directlyCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: That sustainability ratings differ by set type as well as by stock.States this directlyCitation checked — the work exists and is described correctly
Fish stocks and sustainability
Scientific advice on pelagic stocks and the pressure on them.
- ICES Advice on fishing opportunities, catch and effort — International Council for the Exploration of the Sea (Scientific institute)Relied on for: Advice on pelagic stock status and fishing opportunities.States this directlyCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: Assessment of pelagic fisheries by gear and stock.Background and mechanism onlyCitation 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 purse seine gear and the distinction between free-school and aggregating-device sets in bycatch terms.States this directlyCitation checked — the work exists and is described correctly
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: That sustainability ratings for purse-seine fisheries differ by set type as well as by stock.States this directlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.