Techniques of cultivating silver carp and bighead carp fingerling in cage with small and medium-sized reservoirs as provenance base

As the main drinking water source in Beijing, Miyun Reservoir plays an important role in the economic development and social stability of the capital. In order to scientifically transform nutrients and aquatic organisms in the water body of the Miyun Reservoir, purify the water quality, and protect the "water of life" in the capital, the Miyun county government increased the amount of fish species after canceling the cage @ # @ 233 fish. Every year, 485000 kilograms of silver carp, bighead carp, bream, grass and other fish species are released to the Miyun reservoir, with the aim of reducing the nutritional load of the water body through fishery production. However, there are some problems that need to be solved in the practice of fish release, namely: the contradiction between ① release and fishing; ② changing autumn release to spring release, the cost is high, and the provenance is not guaranteed; the fish species purchased by ③ and long-distance transportation cause fish species damage, so that the survival rate of release species is relatively low. The fish species in ④ ponds occupy tens of times of the water area of cage culture, and it is not easy to control healthy culture. Therefore, it is necessary to take small and medium-sized reservoirs as provenance base and use cage technology to cultivate silver carp and bighead carp fingerling to solve the above contradictions, to ensure the survival rate of released fish species and to effectively control the species, quantity and quality of released fish fingers. to achieve the goal of "purifying water, promoting fishing and enriching the people".

I. necessity and feasibility

1. The first is that silver carp, bighead carp, common carp, grass, bream and other fish can make effective use of plankton, benthos, aquatic plants, organic detritus and other substances, which play an important role in biological water purification. to ensure the need for fish fry needed to improve water purification capacity by biological methods in Miyun Reservoir. Second, as the breeding base of Miyun Reservoir, it can timely produce, release and catch adult fish according to the law of fish growth, effectively avoid the loss caused by wrapping fish species during adult fishing, and improve the survival rate of fish fingers. the need to solve the contradiction between proliferation and fishing, and the need to solve the contradiction between species release and fish production. Fourth, it is an effective way to carry out healthy aquaculture and reduce aquaculture waters and improve ecological, social and economic benefits.

two。 It is feasible to determine the species and quantity of released fish species according to the fish productivity provided by natural bait organisms in Miyun Reservoir. In June 2006, Shachang Reservoir (a medium-sized reservoir) was used and farmers in the reservoir area used net cages to cultivate fish fingers. to ensure the quantity and quality of released fish species in Miyun Reservoir, so as to achieve the goal of "purifying water, promoting fishing and enriching the people". The fish productivity of filter-feeding fish in Miyun Reservoir provided by plankton is about 19.8kg/ mu. Starting from the goal of water purification, the fish species structure is adjusted so that silver carp and bighead carp account for 70% of filter-feeding fish production. The initial fishing standard of silver carp and bighead carp is set as 1.5kg/ tail, and the discharge of silver carp and bighead carp species is about 45 / mu ~ 52 / mu according to the survival rate rising from 7.5% to 20%. Due to the great change of water level in Miyun Reservoir, the quantitative analysis of water-bearing plants is difficult to be accurate, so the discharge of grass, bream bream and other fish can only be estimated according to the relationship between multi-year discharge, catch and fish growth rate. According to the catch statistics of 20 years, the fish productivity of herbivorous fish is about 0.6kg/ mu ~ 0.8kg/ mu, and the starting fishing standard of grass carp is 1.5kg/ tail and that of carp is 0.5kg/ tail. The recapture rate is calculated at 20%, and the discharge of grass, bream bream and other fish species is about 3 / mu ~ 4 / mu respectively. The existing water surface area of Miyun Reservoir is about 137000 mu, the discharge of silver carp and bighead carp is about 8 million, and that of grass, bream and herring is about 1 million.

Materials and methods

1. The water area of Shachang reservoir is 2250 mu, and the water quality meets the fishery water quality standard. the cage is located in the sunny part of the west bay of the reservoir, and the water depth is more than 5m. The single-layer enclosed cage is adopted, the specification of the cage is 5m × 5m × (2cm) m, the depth of the cage is 1.5m~2.5m, the surface of the water is 0.5m. The total number of cages: 5m × 5m × 2m PE polyethylene warp knitted single-layer cages with 0.8cm mesh, 5m × 5m × 3m PE polyethylene warp knitted single-layer cages with 1.5cm mesh. The box frame is a square frame bundled with four Chinese fir trees of 5cm~10cm in diameter. The specification of the frame is 5.2m × 5.2m. One steel bar pillar with diameter 1.4cm and high 50cm is installed at the four corners and the midpoint of the four sides of the frame to support and fix the cage. The cages are arranged in the shape of "one", every 25 ~ 30 sets are in a row, each row is 50m apart, and each box is 1m~2m apart.

two。 Summer flower fingerling silver carp, bighead carp, grass, bream, green and other fish come from Yukou fishing ground in Pinggu District. The time of entering the box is June 22-28, 2006, and the stocking density is 86000 fish per box, that is, 52000 silver carp per box, 34000 bighead carp per box, a total of 50 boxes, 130000 grass carp per box, a total of 2 boxes, and 104000 carps per box, a total of 1 box. 12000 herring summer flowers were put into use on July 10th, totaling 1 case. From August 8 to 15, silver carp and bighead carp were divided into 100 boxes, grass carp into 4 boxes, carp into 2 boxes, and herring was still divided into 1 box, a total of 107 boxes.

3. The fineness of feed for silver carp and bighead carp fry requires that all raw materials reach more than 80 mesh, and the second crushing fineness of compound feed reaches 60 mesh. Grass, bream, green and other fish species are all made of open micro-particles. Feed quality requirements: 38% feed containing crude protein is used when the fish body specification is below 5g/ tail, 34% feed containing crude protein is used when fish body specification 5g/ tail ~ 15g/ tail, and 31% feed containing crude protein is used when fish body specification 15g/ tail ~ 25g/ tail. Domestication and feeding began on the second day after the fish were put into the box. At the beginning, they were fed twice a day. After about 3 days of domestication, the fish could be successfully domesticated. After concentrated feeding, the feeding frequency will be gradually increased to 6 times a day, each box feeding time is about 10 minutes, mainly sprinkled dry powder, in case of windy weather, can be mixed with water to feed, according to the different specifications of fish species, stocking density and fish growth, water quality, climatic conditions and other flexible control, under normal circumstances, the daily feeding amount is 3% and 8% of the total fish weight.

4. Daily management to keep the water quality in the box fresh and clean the cage with branches every 7 days after the fish is put out of the box. Always check the cage for damage and loopholes to prevent the fish from escaping. Check the water temperature, observe the feeding and activity of fish species, adjust the feeding amount at any time, and make a good culture record.

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