First, the ecological crab, fish net polyculture pattern 1. Principles The amount of aquatic weeds in the culture zone is used as the maximum amount of feed for ingestion of fish to determine the number of grass carp species to be put in, so that the aquaculture coverage rate will remain at 65% during the period from April to October. It was restored to 95% between November and March of the following year in order to maintain the normal vegetation coverage in the farming area. During the cultivation period, appropriate areas of bare vegetation should be maintained to increase the visibility of artificial feed on the bottom of the water and improve feed utilization. Through the agitation of the grass carp in the culture area, the oxygen source of sediment in the culture area is increased, and the oxidation of nitrifying bacteria to the ammoniated product in the nitrogen cycle is promoted to accelerate the nitrogen circulation rate. Improve dissolved oxygen at the bottom of the culture area, increase the bait conversion rate of the cultured objects, and lower the feed coefficient. Make use of the complementary advantages of crab and grass carp in diet and niche. The residual bait of the grainy crab feed and the broken-off grass caused by the crab grass after herbivory can be used by the grass carp. This not only reduces the spoilage effect of the residual bait in the water, but also achieves the purpose of fully utilizing the bait. 2. Farming model features Eco-type crabs, fish nets around the polyculture model mainly to raise crabs, supplemented by fish farming. The amount of crabs and the amount of crabs were reasonable. The technical route of combining natural bait and artificial bait was used to strictly control the input of the external bait and changed the traditional farming methods of mowing the grass outside the culture zone. It not only protects the vegetation resources in the culture area, but more importantly, the nitrogen and phosphorus input in the whole cultivation process is controlled at a relatively low level, and the total nitrogen and total phosphorus contained in the crab species, fingerlings, and exogenous artificial diets are achieved. Less than the total nitrogen and total phosphorus contained in adult and adult fish production. 3. Implementation results and economic benefits: 3 kg of mussels and 25 kg of grassy fishes, 28.8 kg of crabs, 75 kg of grass carp and 103.8 kg of mu per mu. Mu 36.9 kilograms of corn, 22.15 kilograms of snail miscellaneous fish, consumption of 1,400 kilograms of aquatic plants. The economic benefits per mu are shown in Table 1. Table 1 Economic Benefits of Fish Crab and Fish Mixed Culture ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€â”€äº§é‡ Output (kg/acre)│ 28.8 │ 75 │├────────┼─────┼────┤│ Group weight gain Multiples │ 9.6 │ 3.0 │├────────┼───────┴────┤ │ Total investment (yuan) │ 2102 │├────────┼──── ─────────────────────────────────────────────────────────────────────────────────────────────┤ 总 总 40 40 40 40 40 40 40 40 40 40 40 40. 93 │├──────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── ─ ┘ ┘ 网 网 网 网 网 网 网 网 网 网 网 网 网 网Principles According to the differences in the diet of fish and crab, the method of raising fish in the year and raising crabs every other year are adopted to optimize the culture environment and optimize the breeding environment. When the fish are in monoculture condition, grasses in the culture area are not long enough, causing serious damage to the vegetation. At the same time, bait sedimentation is caused by feeding and the amount of residual bait is continuously increased in the same culture area. Increase, have a certain influence on the surrounding water quality. However, the residual bait deposition also increases the enrichment of nutrients in the sediment, which is beneficial to meet the nutritional requirements for the growth of aquatic plants in the following year. At the same time, it can also significantly increase the biomass of benthic animals in the culture area. Therefore, using fish and crabs to raise fish, the fish farming area is converted into a crab-raising area every other year, which not only provides a good environment for aquatic grasses in the breeding area, but also provides a rich benthic food for crabs. The planned artificial planting of aquatic plants in the culture area has also achieved the effect of artificially modifying the vegetation structure in the lake area. 2. The characteristics of aquaculture model The type of web-round rotation technology is mainly based on fish farming, and crab is an ecological control method. Taking 120 acres of aquaculture area as an example, it is divided into A and B two blocks of 60 acres each, using the A area to cultivate fish and nesting the crab species, and turning the crab cultivation area into a single raising crab the following year. In Area B, crabs were cultivated in the same year, and fish were reared in the following year, and crabs were reared in the breeding area. The districts A and B were formed to exchange farm layouts every other year (see Figure 1). In the four experimental areas in Figure 1, three acres were circling in each of two 60-mu plots as a crab breeding area. The dates for the release of fingerlings from the adult fish culture zone: Area A in February, from the date of arrest in October of the year to January of the following year, 54 acres. Crabs from the breeding area dunk crab release date: A zone in July, 6 acres. Crab species will be harvested in February of the following year. Crab species in adult crab breeding area Date of delivery: Area B, February, dates from October to November. Rotation method: In the following year, the breeding species in Area A was interchanged with Area B. Area B was used as a breeding area for crabs and a breeding area of ​​6 acres and a breeding area of ​​54 acres. A area was used as a breeding area for crabs and 60 acres. Crab species came from the previous year. 6 mu of crabs are grown in the breeding area. Breeding methods: adult fish breeding mainly based on plant feed, combined with some grain feeds; adult crabs feeding artificially fed grain feeds combined with animal feeds; artificial control of crabs in semi-starved areas, average daily feeding amount Control 2% of the total weight of crabs. 3. Implementation Effect and Economic Benefits The network round rotation mode solved the problem of crab self-sufficiency in crab breeding. 6 acres of crabs in the breeding area, the average area of ​​4.17 kg of loose-leaved crabs, acre yields 43.65 kg of large-sized species of crabs; 54 acres of fish breeding areas, 160 kg of acres of fish, 602.1 kg of fish production; 4.3 kg and 34.65 kg crabs produced per mu. The average annual net profit is 1360.77 yuan, and the input-output ratio is 1:1.464. 4. The ecological benefit analysis has greatly reduced the demand for aquatic weed resources outside the aquaculture area through rotational breeding in the encircling area, which is of great significance for the protection of vegetation in the entire lake area. Adopting rotational breeding is beneficial to the efficient utilization of food organisms in the breeding area. At the same time, artificial cultivation of black algae in the cycle of breeding crabs changes the original vegetation structure in the breeding area and provides fish for the fish cultured in the next year. The eating and drinking plants have achieved the purpose of complementing the habitat, complementing the biological resources of the feed, and comprehensive utilization. The nitrogen input to output ratio is 1:1.55; the phosphorus input to output ratio is 1:1.33. The entire nitrogen and phosphorus accounting for breeding is a negative growth.
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