1. Cage Composition
It is composed of box, frame, float, sink and fixed facilities.
(1) Box body: stitched and spliced by nettings according to a certain size. At present, the most common application is polyethylene netting, which has the advantages of high strength, corrosion resistance, low temperature resistance, and low price. There are four processing techniques for the netting: ①Polyethylene stranded knotted handmade net , The advantage is that it is flexible and durable. The disadvantage is that there are nodules, which can easily scratch the fish body, use a lot of materials, and have poor water drainage; ②Non-extended knotless net ,This process is fast in production, saves materials, and is cheap, but it has poor lateral tension and is easy to break; ③Extend knotted netting ,It has strong tensile force, softness and light weight, and its cost is 3/4 lower than that of nodular cages; ④Polyethylene warp-knitted netting. No knots and smoothness, no damage to the fish body, the mesh is shaped and not out of shape, the box body is soft, easy to sew, not easy to open holes to escape the fish, and the cost is low.
(2) Frame: It is a bracket for hanging the box, which is usually composed of bamboo, wood, steel pipe, plastic pipe and other materials. Fixing the box on the frame can keep the box open and shaped.
(3) Float: It is a device used to float the net cage on the water. Commonly used floats made of foam plastic and rigid blow molding, or use glass balls or iron buckets to tie on the frame as floats. The bamboo and wooden frame supports the box body and also functions as a float.
(4) Sinker: It is a device that makes the bottom of the cage sink in the water. Porcelain sinkers are generally used, stone blocks, cement blocks, etc. can also be used. Conditionally, steel pipes with a diameter of 2-2. 5 cm can be used, which can not only open the bottom net, but also can be used as a sinker.
In addition, iron anchors should be used to fix the position of the cages, or cement piles or bamboo piles should be used to support the cages.
2. The Shape of the Fishing Cage
There are rectangular, square, cylindrical, octagonal, etc. At present, the most commonly usage, it is the rectangles shape, followed by squares, because of its convenient operation, large water-passing area, and convenient production.
3. The Size of the Cage
The smallest cage has an area of about 1 square meter, usually 1-15 square meters are small-sized cages, medium-sized cages with an area of 15-60 square meters, and large-scale cages with an area of 60-100 square meters. The larger ones have 500-600 square meters. Generally speaking, the area of the cage should not be too large, because it is inconvenient to operate and has poor wind resistance. However, although the output of too small cages is high, the cost is high. At present, most of the cages with a size of 10-30 square meters are used, that is, 7×4 meters, 5×3 meters, 3×3 meters, 3×4 meters and other specifications.
4. The Height of Fishing Cage
The height of the cage is determined by the depth of the water body and the vertical distribution of plankton. At present, it is mostly used between 1.5-2.5 meters high. Cages with a height of about 2-4 meters can also be used for the depth of the water body. However, the distance between the bottom of the cage and the bottom of the water should be at least 0.5 meters, so that the bottom waste can be discharged from the cage.
5. Mesh size
The size of the cage net should be determined according to the breeding object, so as to save materials as much as possible and achieve the principle of the highest exchange rate of the cage water body. The net mesh is too small, not only increases the cost of the cage, but also affects the exchange and renewal of the water flow; the net mesh is too large, and the phenomenon of fish escape occurs again. Usually stocking 4 cm summer flower fingerlings, use 1.1 cm net cages; for stocking 11-13 cm first-year-old fingerlings, use 2.5-3 cm net cages; grow-out cages , Use a 3-5 cm mesh net cage. In order to make the water exchange smooth and reduce the number of cages flushing, it is best to switch to larger net cages as the fish grow up.