Civilization101Blueprint

Gill net

A wall of near-invisible mesh that fishes a whole channel while you do something else.

Build Tier 1 · Neolithic Food Moderate — the netting is long, not hard 8–20 person-days for a 20 m net Crew 1–2 to make, 2 to set

Home: Wild food, Level 0 · Triage, level 1 of 1 in its track. Serves 3 steps across 2 subjects.

Every build on this site has hazards that injure or kill — quicklime, carbon monoxide, molten metal, collapsing ground. Read the safety notice before starting, and read this build's own failure modes below.

Fish held by the gills in the mesh — the whole principle of the net, and why mesh size selects the catch. Checking gill nets · Pedro Ramirez, U.S. Fish and Wildlife Service · Public domain · Commons ↗

What it is and why this shape

A trap catches fish that come to it. A net intercepts everything moving through a piece of water. Set across a channel, along a weed edge or around a shoal, it fishes a volume rather than a point, and it does so all night.

The mechanism is precise, and understanding it is what makes the net work: a fish swims into a mesh it cannot see, its head passes through, its body does not, and it is held behind the gill covers when it tries to back out. That means a gill net catches a narrow band of sizes — everything smaller swims through untouched, everything larger bounces off. That selectivity is not a limitation. It is the single most valuable property the gear has, because it lets you take the adults and leave the juveniles.

Two numbers do almost all the work: mesh size, which sets what you catch, and hanging ratio, which sets whether the net fishes at all. Both are covered below, and the second is the one that is almost always got wrong.

Making the net is a long, patient job — twenty person-days is realistic for a first one. It is also the single best return on that time available in tiers 0 and 1.

The rig, set Fig 1
Earth / subsoilMetalGravel / aggregateWaterFire / hot zoneVoid / air
The net is a wall standing in the water column: floats up, weights down, slack in between. Fish it across the direction of travel — across a channel, along a weed edge, or around the outside of a shoal.
Hanging ratio — the number that decides everything Fig 2
WaterFire / hot zone
Hang the net to about half its stretched length. Pulled tight the mesh is a flat wall a fish bounces off; hung slack it becomes a loose, three-dimensional trap that a fish drives into and tangles in. This one ratio separates a net that fishes from a net that does not, and it is the mistake almost everyone makes first.

Keyed parts

1Headline with floatsHolds the top edge up. Floats sized so the net stands even when loaded with fish.
2Footrope with weightsHolds the bottom down. Heavier than seems necessary — a lifting footrope lets everything under.
3Netting panelThe mesh itself. Made in rows against a gauge; see the fishing guide for the knot.
4Hanging twineTies the mesh to the ropes at intervals, setting the hanging ratio.
5SelvedgeA heavier reinforced row of mesh top and bottom, taking the load off the fishing mesh.
6Anchors or stakesOne at each end. In current, both must hold considerably more than they look like they need to.
7Marker floatsAt each end. An unmarked net is a hazard to boats and gets lost.
8Bag of slackThe loose belly created by hanging at 50% — this is what tangles and holds the fish.

Specifications

Set length20 mHeadline length. Start shorter — a 10 m first net teaches the same lessons in half the time
Netting made40 m stretchedTwice the set length. This is the hanging ratio
Hanging ratio0.5The critical number. 0.45–0.55 is the working range
Fishing depth2.0 mOr the water depth, whichever is less. A net taller than the water lies on the bottom and fouls
Stretched mesh≈ ¼ to ⅓ of target fish lengthApproximate — body shape varies enormously by species. Test locally and adjust
Twine diameteras fine as will holdFish see and feel thick twine. Fineness is the difference between a good net and a mediocre one
Float spacing1.0–1.5 mEnough lift to hold the headline up with a loaded net
Weight spacing1.0–1.5 mHeavier than feels right. A lifting footrope lets everything swim underneath
Selvedge2–3 rows, heavier twineTop and bottom. Takes the load so the fishing mesh does not
Soak timeovernightSet at dusk, lift at dawn. Longer and the catch spoils in the water

Bill of materials

MaterialQuantityNotes and substitutes
Netting twine≈ 1.5–3 kgFine, strong, rot-resistant. Flax, hemp, nettle, dogbane, or scavenged synthetic line — synthetic is far better if you have it, being finer, stronger and rot-proof.
Headline22 mStronger than the netting; it carries the whole load.
Footrope22 mSame, plus the weights.
Floats15–20Cork bark, dry light wood, sealed gourds, bundled reed. Substitute: anything that floats and will not waterlog.
Weights15–20Stones grooved or wrapped, fired clay rings, or lead if available.
Hanging twine≈ 30 mFor tying mesh to ropes at measured intervals.
Anchors2Stones or stakes. In current, considerably heavier than you expect.
Marker floats2Visible, and distinctively yours.
Netting needle and mesh gauge1 eachWhittled in ten minutes. The gauge is what makes the mesh regular — see the fishing guide.

Tools: Netting needle · Mesh gauge · Knife · A frame or two posts to hang the work from

Construction

Choose the mesh before you start

Decide what you are fishing for and cut the gauge to suit. As a starting point, stretched mesh of about a quarter to a third of the target fish's length. This decision is irreversible — the mesh cannot be changed once the net is made, and it determines both what you catch and whether you leave juveniles alive.
✓ Check: Gauge cut, and a sample of five meshes measured stretched to confirm.

Make the netting

Row by row against the gauge, using the sheet-bend netting knot from the fishing guide. Work to a fixed row count for the depth and keep going for the length. This is the long part — days of it — and consistency matters far more than speed. An irregular net fishes unevenly and tears at its smallest meshes.
✓ Check: Any ten consecutive meshes measure the same within a couple of millimetres.

Add selvedges top and bottom

Two or three rows of heavier twine along each edge. These take the strain from the ropes and the fish, so the fine fishing mesh never carries load. A net without selvedges tears along its top edge on the first heavy catch.
✓ Check: Selvedge twine is visibly heavier and the rows are even.

Hang it at 50%

Lay out the headline and mark it every metre. Take two metres of stretched netting to each one metre of rope and tie it off at each mark with hanging twine. Repeat on the footrope. Measure and mark — do not judge this by eye, because the temptation is always to pull it tighter and tighter is wrong.
✓ Check: 40 m of stretched netting has gone onto 20 m of headline, and the panel hangs in visible slack bags.

Fit floats and weights

Floats along the headline, weights along the footrope, at roughly matching spacing. Test in water: the net should stand upright with the headline just at or below the surface, and stay standing when you pull on it. Add weight until the footrope stays down.
✓ Check: Floated in the shallows, the net stands as a wall rather than lying over.

Set it across the traffic

Across a channel, along a weed edge, or around the outside of a shoal — always across the direction fish are travelling, never along it. Anchor both ends properly. Mark both ends visibly, for your own sake and for anyone else on the water.
✓ Check: Both ends hold against a hard pull, and both markers are visible from the bank.

Set at dusk, lift at dawn

Overnight is the productive soak. Longer and the catch dies and spoils in the water, which wastes the fish and fouls the net. Lift by taking the headline and footrope together so fish do not drop out.
✓ Check: Fish lifted are fresh, firm and clear-eyed — not soft or bloated.

Clear, dry and repair after every lift

Pick out every fish, every weed strand and every stick. Then dry the net completely before storing — a natural-fibre net stored damp rots within weeks and is the commonest way to lose one. Repair holes immediately; a small hole becomes a large one on the next set.
✓ Check: Net dry to the touch throughout, and no hole larger than a single mesh.

Move it, and rest the water

Rotate between several sets. When the catch per night starts falling in one place, that water is being fished down — move, and leave it alone. During spawning runs, take the net out entirely.
✓ Check: A written record of set location and catch. The trend is what tells you when to stop.

Tolerances that matter

DimensionTargetWhy it matters
Hanging ratio0.45–0.55Outside this the net either bounces fish off or hangs in a useless heap. It is the single most important number in the build.
Mesh consistency±2 mmIrregular mesh fishes unevenly and tears at the small meshes under load.
Footrope weightenough to stay down loadedA lifting footrope lets every fish pass underneath, and the net looks perfectly fine while catching nothing.
Twine finenessas fine as will holdFish detect and avoid heavy twine, especially in clear water and daylight.
Drying before storagebone dryNatural-fibre nets rot in weeks if stored damp, and the rot is invisible until the net fails.

How this fails

Hanging the net tight. The commonest and most complete failure: a taut mesh wall that fish simply bounce off. It looks like a better net and catches almost nothing.
Under-weighted footrope. Everything swims under. From the surface, the set looks perfect.
Mesh too small. Takes juveniles, strips the water within a season or two, and ends the fishery. This is the failure that costs the most and shows up latest.
Storing the net damp. Rots from the inside, silently, and the net fails on a set with a full catch in it.
Leaving it set for days. Fish die and rot in the mesh, the net stops fishing, and you have killed a catch for nothing.
Leaving it unmarked, or abandoning it. A lost net goes on fishing indefinitely with nobody to lift it — killing continuously and catching nothing for anyone. If a net cannot be recovered, it must be cut down and removed.
Fishing a spawning run with a net across the whole channel. The fastest way to end a fishery permanently. Leave a passage; take it out entirely during the run.

How you know it worked

VerificationAn overnight set produces fish consistently, the catch is within a narrow size band with small fish passing through untouched, and the catch rate at a given location has not declined over a season.

Scaling and variants

Smaller and far quicker: a 5–8 m net for a stream mouth or a weed edge can be made in a few days and teaches everything — knot, gauge, hanging ratio — at a quarter of the cost of getting it wrong.

Seine net: the same netting, hung with a heavier footrope and hauled through the water by two people rather than left standing. It takes everything in its path rather than a size band, which makes it enormously productive and much easier to over-fish with. Reserve it for occasional bulk harvest, not routine use.

Trammel: three layers — a fine mesh loosely hung between two coarse ones. A fish pushes the fine mesh through the coarse and is bagged. Catches a far wider size range than a plain gill net, which is exactly why it should be used carefully.

Where a net is the wrong tool: fast rough water, heavy weed and snaggy bottoms will destroy a net in one set. Use traps there.

The same thing, built

Knotting net by hand in Ibeno, Nigeria. Mesh size and hanging ratio are both decided at this stage. DEC2025 A woman from Ibeno weaving fishing net 01 · 2025-12-07 · EnnyOch · CC BY-SA 4.0 · Commons ↗
Hauling a set gill net back onto the beach, Colombia. Pescadores La Mochila · 2009-03-17 04:02:53 · Fany mcGhan y Laurie Batista · CC BY-SA 3.0 · Commons ↗