|Better Farming Series 38 - Better Freshwater Fish Farming: Raising Fish in Pens and Cages (FAO, 1990, 83 p.)|
41. A pen can be small or large depending on how many fish you want to raise.
42. However, when you first begin, start by building a small pen. You will need fewer materials. It will be easier to take care of.
43. You can begin with a pen that has about 100 square metres (10 by 10 metres). Later, when you have learned more, you can build bigger ones.
44. A pen is closed by a fence. So, start by driving a row of posts. Posts can be made either of bamboo or wood.
45. If you are using wood, choose wood that does not rot quickly when it is in the water.
46. The posts should be long enough to be driven firmly into the bottom. They should also be long enough to reach at least 50 centimetres above the highest water level.
47. Posts should be 1 to 2 metres apart depending on the material that you use to close the pen.
48. The best material for the fence of the pen is ordinary fish net. You can also use plastic mesh, or woven material made from split bamboo or wooden strips.
49. If you are using fish net to close your pen, the posts can be further apart. If you use woven material or plastic mesh, the posts may have to be closer together.
50. The openings in the material that you use to fence in a pen must be small enough to keep the smaller fish from getting out.
51. However, if the openings are too small they may become filled with dirt or with the very small plants that grow in the water.
52. If the openings in the material become filled with dirt, fresh water will not flow through to clean out the pen and the fish may not have enough air.
53. So, be sure to use material with openings of 1.5 by 1.5 centimetres. This is the right size to keep in the smaller fish and also to let fresh water flow through.
54. Whatever material you use for the fence, it should be high enough to be buried in the pen bottom at least 30 centimetres deep.
55. It should also reach to the top of the posts which, you were told in Item 46, should be at least 50 centimetres above the highest water level.
56. This will keep your fish from getting out of the pen along the bottom or jumping out over the top.
57. Now you will be shown how to build two kinds of pens, how to attach the fence material and how to bury the material in the bottom.
Put a pen along a bank
Put a pen away a bank
mark the place where you will put the fence using wooden stakes or poles and a piece of heavy line
Put a fence
Put a fence
check the bottom along the line with a long pole to see how far you will have to drive in the posts so that they will stand firmly
Check the bottom
measure the depth of the water every 2 metres along the line
Measure the depth
remember, all posts must be at least 50 centimetres above the
highest water level
so, each post must be long enough to reach 50 centimetres above the water, plus the depth of the water, plus the depth that each post must be driven into the bottom
now you can cut all of the posts to the proper length
Cut the posts
drive in the posts along the line 1 to 2 metres apart, depending on the kind of fence material that you are going to use (see Items 47 to 49)
be sure to use material that is high enough to be buried at least 30 centimetres in the pen bottom and that can also reach the top of the posts
if you use fish net for the fence, tie the edge- line of the net to the top of the posts using strong cord
Use strong cord
if you use woven material for the fence, tie it to the posts with strong cord or you can use strong vines
Use strong vines
if you use plastic mesh for the fence, fasten it to the posts with wire
Use plastic mesh
when the fence material is well fastened to the posts, you are ready to bury the material in the pen bottom
you can bury fence material by pushing it into the pen bottom and putting a row of stones on either side to keep it in place
Use fence material
you can also bury fence material by fastening it to straight poles and pushing the poles into the pen bottom with wooden stakes to keep it in place
Use wooden stakes
note: to bury fence material you may have to work under the water
58. When your pen is finished, cut the weeds and grass on the banks clean out most of the plants in the water and take away any rubbish that you find.
59. Then, remove the unwanted fish, crabs or other water life in the pen. You can do this using a fine- mesh net.
Use fine- mesh net
60. When you have done this, you are ready to stock your pen with baby fish.