Mesh Size Selection

Part of Fishing

The mesh opening in your net determines which fish you catch and which escape — get it wrong and you’ll pull an empty net from the water every time.

The Principle

A gill net catches fish by their gill covers. The mesh must be large enough for the fish’s head to push through but small enough that its body cannot follow. When the fish tries to reverse, its gill covers flare out and lock in the mesh.

This means mesh size is directly tied to fish body circumference. There is no universal “right” mesh size — it depends entirely on what fish live in your water and which ones you want to catch.

How Mesh Is Measured

Mesh size is the stretched distance between two opposite knots in one diamond-shaped opening. When you pull a single mesh opening taut between two fingers, the distance between the knots is the mesh size.

Your mesh gauge (the flat piece of wood you wrap line around while tying) is half the mesh size. A 2.5 cm (1 inch) gauge produces 5 cm (2 inch) mesh.

   Knot
    / \
   /   \    ← Mesh size = distance
  /     \      between top and bottom
  \     /      knots when stretched
   \   /
    \ /
   Knot

Mesh Size by Target Species

The following table covers common freshwater and coastal species you’re likely to encounter. Sizes are approximate — local fish vary in body proportions.

Target Fish	Body Length	Recommended Mesh Size	Gauge Width
Minnows, shiners, small baitfish	5-10 cm (2-4 in)	2-2.5 cm (3/4-1 in)	1-1.25 cm
Bluegill, perch, small panfish	12-18 cm (5-7 in)	3-4 cm (1.25-1.5 in)	1.5-2 cm
Trout (small to medium)	20-30 cm (8-12 in)	4-5 cm (1.5-2 in)	2-2.5 cm
Bass, walleye, large trout	30-45 cm (12-18 in)	6-8 cm (2.5-3 in)	3-4 cm
Carp, catfish, pike	40-70 cm (16-28 in)	8-10 cm (3-4 in)	4-5 cm
Large salmon, large catfish	60-90 cm (24-36 in)	10-13 cm (4-5 in)	5-6.5 cm
Mullet, herring (coastal)	20-35 cm (8-14 in)	5-6 cm (2-2.5 in)	2.5-3 cm
Shrimp, prawns	8-15 cm (3-6 in)	1.5-2 cm (1/2-3/4 in)	0.75-1 cm

How to Determine What’s In Your Water

Before making a net, figure out what lives in your waterway.

Step 1. Observe. Sit quietly by the water at dawn or dusk for 30 minutes. Watch for:

• Surface splashes (indicates fish size — bigger splash, bigger fish)
• Fish jumping (you can estimate body length)
• Shadows in shallow water
• Fish holding in current seams or near structure

Step 2. Test fish with hook and line. Catch a few fish by hand line. Measure them. This tells you both what species are present and what size they are.

Step 3. Ask locally. Other survivors who have been fishing the same water will know what’s in it. Traditional knowledge is invaluable.

Step 4. Examine evidence. Look along the bank for:

• Fish bones from animal kills (osprey, otter, bear feeding sites)
• Dead fish washed up
• Scales stuck to rocks where someone cleaned a catch

The 30% Rule

A practical rule of thumb: mesh size should be approximately 30% of the target fish’s body length.

• A 30 cm (12 inch) trout needs about 9 cm mesh at the body — but the mesh catches at the gills, which are closer to the head. In practice, 4-5 cm mesh works for this fish.
• The actual relationship is between mesh size and the fish’s maximum head circumference. Since you rarely get to measure a live fish’s head, the 30% rule gives a reliable approximation for most species.

If you’re unsure, err slightly smaller. A mesh that’s slightly too small will still catch fish — they get tangled in it even if the head doesn’t fully pass through. A mesh that’s too large catches nothing.

Multi-Species Strategy

In most waters, you’ll have fish of several species and sizes. You have three options:

Option 1: Target the Most Common Size

If most fish in your water are a similar size (e.g., a creek full of 20-25 cm trout), size your mesh for that group. You’ll miss the small ones and the big ones, but you’ll consistently catch the majority.

Option 2: Build Multiple Nets

If you have the cordage and time, build two nets — one with smaller mesh (3-4 cm) and one with larger mesh (7-8 cm). Set them in different locations or at different depths. This covers the widest range of species.

Option 3: Graduated Mesh

Build a single net where the mesh size increases from one end to the other. Start with 3 cm mesh at one end and gradually increase the gauge as you weave, reaching 8 cm at the other end. Set the small-mesh end in shallower water near shore (where smaller fish tend to be) and the large-mesh end in deeper water.

This is harder to build but very effective in mixed fisheries.

Common Mistakes

Too large mesh. The most common error. Beginners overestimate fish size and make mesh too large. Fish swim right through the net. When in doubt, go smaller.

Inconsistent mesh. If your gauge slips or you change tension while tying, the mesh openings vary. Some will be too large (fish escape), others too tight (fish bounce off). Use a rigid gauge and maintain consistent tension throughout.

Not accounting for material stretch. Plant fiber cordage stretches when wet, expanding the mesh 10-15%. Natural fiber nets should be tied with mesh slightly smaller than your target — they’ll stretch to the right size in water. Synthetic line (nylon, paracord) stretches very little.

Setting the net in the wrong depth. Different fish species prefer different water depths. Panfish and minnows stick to shallows. Larger predatory fish patrol deeper water. Match your net depth and position to the behavior of your target species.

Testing Your Mesh Size

After building your net, test it before committing to a full deployment.

Step 1. If you’ve caught any fish by other methods, hold the net mesh against the fish. The head should push through the opening while the body does not. The gill covers should catch on the mesh when you pull the fish backward.

Step 2. Set a short section of net (1-2 meters) in a likely spot for 12 hours. Check what it caught and what it didn’t.

Step 3. If you’re catching nothing after 24 hours in a location where you know fish exist, your mesh is wrong. Examine the net — are there signs fish hit it and escaped (stretched or disturbed mesh without fish)? If so, go to a smaller mesh size.

Conversion Reference

For quick mental math when you don’t have measuring tools:

Body Part	Approximate Width
Adult fingertip	1.5-2 cm
Adult thumb width	2-2.5 cm
Two fingers together	3-4 cm
Three fingers together	5-6 cm
Four fingers (palm width)	7-9 cm
Full hand span (thumb to pinky, spread)	18-22 cm

Use these to estimate your gauge width when precision measuring tools aren’t available.

Key Takeaways

• Mesh size is the single most important variable in gill net fishing — wrong size means zero catch.
• Use the 30% rule: mesh size equals roughly 30% of your target fish’s body length.
• When in doubt, go slightly smaller — fish still tangle in tight mesh, but they swim through oversized mesh.
• Observe your water first: know what lives there before you spend hours building a net.
• Natural fiber nets stretch 10-15% when wet — tie mesh slightly small to compensate.