Experience of rotational culture of Macrobrachium rosenbergii and mandarin fish

Macrobrachium rosenbergii is not tolerant to low temperature. When the water temperature drops to 15 ℃ in late autumn and early winter, it is necessary to start fishing in dry ponds in time, so that Macrobrachium rosenbergii culture ponds can only be used for half a year (from May to October). Mandarin fish do not stop feeding completely in winter and continue to grow, but the feeding intensity and growth rate slow down. The mandarin fish was cultured in Macrobrachium rosenbergii culture pond during the winter fallow period, at this stage, the seedlings were cheap, the bait fish were rich, and the mandarin fish were on the market from April to May of the following year, and the price was relatively high. The rotation culture of Macrobrachium rosenbergii and mandarin fish can maximize the idle period of the fish pond, increase the pond output rate and increase the culture benefit.

1 Pond conditions and preparation

1.1 the pond condition and cleaning require that the pond has sufficient water source, convenient drainage and irrigation, an area of 33.5 mu, a flat beach foot, a slope ratio of more than 1 ∶ 3 and an effective water retention depth of 1.2 to 1.5 m. Before releasing shrimp seedlings after temporary culture, dry ponds, cleaning, exposure, and digging ditches with a width of 1m and a depth of 0.5m must be used as shrimp collection troughs, and the ponds per mu should be cleaned with 100kg quicklime dry method, and fresh water should be injected the next day with a water depth of 0.6m.

1.2 planting shelter to plant cabbage on the slope around the pond. Generally, the seeds were sown at the end of April, and in the middle of May, the mandarin fish were cleared and transplanted to the water level of 0.7m on the pond slope, with a planting spacing of 0.1m. When the water level rose, when the water level rose and the water level grew well, it extended to 2cm in the pond, accounting for 5% of the total pond area. As a habitat and molting environment for Macrobrachium rosenbergii.

1.1.3 build an intermediate cultivation pond in the leeward direction of the pond, excavate a rectangular pond with an area of 50m2, with a water depth of 0.8m to 1.2m, build a bamboo shelf and cover it with thin film, and there are nets in the pond for shrimp habitat. Disinfect the shrimp fry with 1kg bleach powder one week before release (about April 15), kill wild fish and bacteria, enter water three days before release (April 22), and heat (heat pump) to keep warm. Macrobrachium rosenbergii seedlings can be released when the water temperature is controlled above 22 ℃.

2 Seedling stocking

2.1Macrobrachium rosenbergii seedlings were stocked around April 25 in the middle culture pond with 100000 desalinated seedlings (2000 seedlings per square meter). In the process of temporary cultivation, the electromagnetic air pump is used to increase oxygen. In the middle of May, when the weather is clear and the water temperature of the pond is more than 20 ℃, remove the thermal insulation film. After the water temperature in the cultivation pond is consistent with the water temperature of the pond, use the net to catch the count and enter the pond. Under normal circumstances, the survival rate of shrimp fry is 60%-70% for about 25 days, the specification is up to 2~3cm, and 3 million mu (1.0-20000 fish per mu) is stocked. 20 days after the shrimp fry are put into the pond, 50 larvae of silver carp and bighead carp are released on June 15 to control planktonic biomass, avoid overfertilizing the water quality, and affect the feeding and growth of Macrobrachium rosenbergii.

2.2Macrobrachium rosenbergii reared in September, most of them have reached the market specification (60 pieces), and can be caught and listed in batches in advance until the dry pond in late October, and the fish are released 10 days after clearing the pond with quicklime, the specification is 0.15~0.2kg per mu, about 50kg; please disinfect the fish before entering the pond.

(3) Culture management

3.1 bait

3.1.1 early propagated shrimp seedlings just entered the greenhouse are mainly fed to Egg Custard, twice a day, 50g each time, seven days later, fed with surimi, soybean milk and other high-protein bait. The feeding amount is 50% of the body weight of shrimp fry, once in the morning, noon and evening, and 60% of the whole day in the evening. At the same time, it is appropriate to increase or decrease depending on food consumption and water quality. After being transferred to the pond for about 25 days, the full-price pellet feed of Macrobran rosenbergii was fed, supplemented by bean cake, wheat flour, wheat bran, small fish and crushed snails. The animal feed accounted for more than 35%, and the daily feed was 20%-40% of the shrimp body weight; two months later, the shrimp was fed at 5%-10% of the body weight. Twice a day, 30% of the daily total in the morning and 70% in the afternoon, while properly feeding some duckweed, silkworm sand and other plant baits rich in molting and other trace elements to meet the physiological growth needs of Macrobrachium rosenbergii.

3.1.2 mandarin fish culture in the first ten days of November, when mandarin fish went into the pond, bait fish were put into the pond at the same time, with the specification of 25,50g white crucian carp, bighead carp fingerling and Loach, starting to release 150kg per mu, and then gradually increasing, with 100 white crucian carp stocked with 0.4~0.45kg. Feeding was carried out in stages, feeding once a week when it was sunny before March, twice a week in March, feeding 15~20kg per mu each time, and increasing according to the weather in April. When the ratio of mandarin fish to feed fish is 1 ∶ (5 to 10), the density of food fish is too sparse, and mandarin fish consume too much physical strength because of preying on food fish, which can not reach the purpose of sufficient feeding and affect the growth; too high density of food fish is easy to cause anoxic floating head. In order to ensure the year-on-year growth of uneaten bait fish, feed an appropriate amount of rapeseed cake at the same time.

3.2 fertilization and water quality management

3.2.1 five or seven days before the temporary culture of Macrobrachium rosenbergii seedlings, fermented organic manure 100kg was applied per mu to cultivate plankton and other natural bait; during the growth period, calcium superphosphate was applied once every 20 days, the amount of 3~5kg per mu, but must not be mixed with quicklime or used at the same time. After entering the pond, Macrobrachium rosenbergii is usually filled with fresh water every 8 to 9 days, and the water level 8~10cm is increased every other week, and the water level reaches about 1.4m two months later. Add some new water every 2-3 days in the high temperature season, and change the new water in time in case of continuous low pressure or cloudy and rainy days. During the peak period of shrimp molting, the water level is moderately lowered during the day to increase the water temperature and promote the hardening of the new shell. Adding new water in the evening is beneficial to the growth of shrimp molting. Patrol the pond once every morning and evening, pay attention to the change of water quality. Once shrimp are found to crawl ashore, you should immediately inject new water or use an aerator to increase oxygen to prevent the death of fish and shrimp caused by hypoxia.

3.2.2 the culture water of commercial mandarin requires rich dissolved oxygen and fresh water quality. Fresh water was injected once in 15-20 days in winter, 10~15cm once in 7-10 days in spring, 20~30cm every time, dissolved oxygen in water was kept above 4mg/L and transparency was kept above 0.4 m.

3.3 Prevention and control of diseases and enemies

3.3.1 the common diseases of diseased shrimp are crustacean disease, black Gill disease and ciliosis. Ciliosis can be sprinkled with 0.6mg/L, a mixture of copper sulfate and zinc sulfate (1 ∶ 1).

In terms of prevention and control methods, ecological prevention should be the main method. For example, from July to September, when the shrimp is in the rapid growth period, it can regularly transplant an appropriate amount of aquatic plants (such as verticillium verticillata) to the shrimp ponds, on the one hand, it can provide a place for Macrobrachium rosenbergii to live and hide. On the one hand, it can avoid the mutual cannibalization of Macrobrachium rosenbergii and the damage caused by leeches, toads, Loach, wild fish and other enemies, on the other hand, it can also improve the ecological environment and maintain the ecological balance of shrimp ponds.

3.3.2 the diseases of mandarin fish prevent the parasitism of anchor head flea during mandarin fish culture, but the harm is not great. Five days before entering the pond, the water was sprinkled with 0.5mg/L concentration of B-type warfarin in the whole pool, the mandarin fish was bathed with salt water and malachite, and every month, the strong insecticide I of 0.25mg/L concentration was used to prevent it. Because mandarin fish are sensitive to most insecticidal drugs, pay attention to the changes of pond fish during sprinkling, and feed the fish in the process of feeding, but go to the pond after medicine bath.

4 harvest and benefit

Macrobrachium rosenbergii income Macrobrachium rosenbergii is reared according to this model to the end of autumn and early winter. During the whole breeding period, the mu of Macrobrachium rosenbergii needs 380kg, the feed coefficient is about 2.4, the survival rate of shrimp is about 75%, the output value of shrimp can reach 160kg, the output value is 8000 yuan, and the income of fish species is about 300 yuan; the cost is about 2280 yuan per kilogram, electricity, pond rent and other artificial miscellaneous expenses are 1000 yuan per mu, and the net profit per mu is more than 5000 yuan.

4.2 income of mandarin fish raised to dry ponds at the end of April and early May, during the culture process, feed fish 600kg, vegetable cake powder 200kg, 150kg per mu (80% of commercial mandarin fish above 0.4kg), silver carp 70kg, total income of 7800 yuan per mu, 2300 yuan of mandarin fish, 2400 yuan of crucian carp and other bait fish, 1000 yuan of artificial miscellaneous expenses such as feed, electricity and pond rent, and a net profit of more than 2000 yuan per mu.

5 Summary

The total net profit of two crops in a year is more than 7000 yuan per mu, which is much higher than that of conventional culture. It is a culture model worthy of further study and trial, but the following three problems must be paid attention to in production.

5.1 Macrobrachium rosenbergii culture adopts the culture mode of early breeding seedlings in the mother pond, full release at one time, multiple fishing and listing in batches, which can prolong the growth period of Macrobrachium rosenbergii for 1-2 months, increase the specifications of adult shrimp on the market and open the marketing period, avoid centralized listing and increase the price. The planting area of asparagus should not be too large, otherwise it will affect the photosynthesis of phytoplankton and lead to hypoxia in water.

5.2 Feed fish should be rich and palatable, and the supply of bait fish should be at least 4 times the weight of commercial mandarin fish. The yield of mandarin fish depends on the quality of mandarin fish: (1) neat specifications, no injury, smooth surface, no parasites and other diseases; (2) control stocking quantity, increase stocking specifications, and improve the listing rate.

5.3 frequent injection of fresh water to keep the water fresh.