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How to Make a Fish Weir With Students

Weirs are one of the most common ancient fishing methods, found in many places around the world, from the Amazon to Ireland to Asia. Modern-day fishermen and scientists still employ weirs to catch fish and count fish populations. A weir is simply a type of underwater fence that may stretch across a stream to catch fish, or a circular enclosure with an inverted opening in a larger body of water. Stone weirs are long-lasting and useful, especially in the sea, but wood-and-wicker types are common and easier to build.

Things You'll Need

Measuring tape
Saw
Heavy lopping shears (optional)
Small limbs and heavy brush, with relatively straight pieces at least three feet long
Small logs or poles, at least 2 inches in diameter, longer than the depth of water
Wire, nylon twine, wicker or rawhide
Rebar, longer than the depth of water (optional)
Shovel or spade
Loose rocks

Instructions

- 1
  Observe the area where you will place the weir. Students can be assigned to determine what kinds of fish are likely to live there and when those fish are most active. They should also observe the strength of the current.
- 2
  Measure the length of the weir. If you are building across a stream, the weir will stretch from one bank to the other. Have the students measure more than once to ensure accuracy.
- 3
  Cut or gather enough brush and small branches to build a weir of the length you need. You will be working in sections approximately three feet long.
- 4
  Trim the branches or brush so that you have relatively straight sections. Use a saw for heavy cutting and to trim the ends; lopping shears will work to clean up smaller twigs. Depending on the age of your students, this may be a job for you and other adult instructors.
- 5
  Lay out the poles in pairs, with one pair every three feet or so. This will permit you to visualize the structure of the weir.
- 6
  Stand up the first pair of poles and either insert the ends vertically into the ground or have students hold them upright.
- 7
  Stand up the second pair about three feet from the first one.
- 8
  Stack the branches and brush between the poles, using nylon twine or wire to tie the bundles to the upright poles. You can also use wicker or rawhide to simulate traditional materials.
- 9
  Repeat Steps 6, 7 and 8 with two more pairs of poles and more brush. Continue building sections in this way until you have enough for your measured length.
- 10
  Carry the bundles to the stream and align them across the water.
- 11
  Insert additional poles into the streambed on the downstream side of the weir and hammer them in. If the current is strong, use metal rebar, unless your students' project requires using traditional materials.
- 12
  Tie the anchored poles to the structure with additional twine, wire, rawhide or wicker.
- 13
  Secure the weir with stones lined along its base on both sides.

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