Techniques of cultivating fish species without bait in reservoir cages

In the reservoir with fertile water quality, using cage to cultivate silver carp and bighead carp without bait is not only feasible, but also has the advantages of not occupying fish pond, no flower fish feed, low cost and so on. Under the condition of not feeding, the cost of cultivating a silver carp species with 13cm in the reservoir by cage is less than 0.10 yuan, while the cost of cultivating a fry of the same size in the pond is more than 0.10 yuan, and the yield is about 150000 fish per mu, which is 30-40 times that of the inner pond. Therefore, the cultivation of fish species without bait in the cage of the reservoir can not only cultivate large fish species, but also has low cost and remarkable benefit.

The success and feasibility of breeding fish species without bait in reservoir cages has its ecological and physiological basis. From an ecological point of view, because the reservoir is a relatively large area of water, the mobility of water makes the various ecological factors and bait in the cage always constant, and will not change much because of the density of fish species. From a physiological point of view, because the highest density is concentrated in a very small range, the activity decreases, which increases the accumulation of nutrients, which is beneficial to the growth of fish. The main cultivation techniques are introduced as follows:

First, the choice of cages. The material commonly used in cages is polyethylene mesh. Screen to the area of 30m2~50m2, deep 2m~3m is appropriate, too large to manage. The size of the mesh depends on the size of the fry, and it is best to change it many times as the fish grows up. Such as 4cm summer flowers to use the mesh for the 1.1cm cage, when the fish grow to 13cm or so, can be changed to the mesh for the 3cm cage.

In general, the cage should choose the reservoir bay where the wind is calm, north to south, and the water depth is about 4m, because these places have high plankton density and more palatable bait for fish. If possible, it is best to have a certain amount of water flow, but not when the speed of the current reaches 2m/s, because the fish will swim in the top current and consume energy, which is not conducive to the growth of fish.

Third, the density of cages should not exceed 1% of the water area even in waters with fatter water quality, and the distance between cages should not be less than 30m, because without baiting and fertilization, the plankton in the natural ecological environment is limited after all.

Fourth, density and collocation. The stocking density and species collocation of fish fry are related to the composition and quantity of plankton in the reservoir and the water exchange capacity inside and outside the cage. Generally speaking, 200 million 300 summer flowers are suitable for each cubic meter of water. In terms of breed matching, silver carp is mainly raised when the water quality is very fat and there are many small plankton; when the proportion of large plankton is large, silver carp should be the main one.

Fifth, daily management. The main work of daily management is to check the cage. When the cage is placed in the water for a little longer, there will be a lot of attachments, which are mainly composed of filamentous algae and some smooth gelatinous bodies. These attachments will block the mesh of the cage and prevent the exchange of water bodies inside and outside the cage. Therefore, cleaning should be carried out frequently. The main methods of removal are mechanical washing (once every half a month), sunlight exposure, biological removal (mixed culture of some tilapia and blunt snout bream that eat these attachments), chemical cleaning (treating the net with copper salt), caisson (sinking under water for 3cm, stop the attachment from photosynthesis, etc.).