Raw fish larvae domestication and fingerling culture

The domestication of fish and the cultivation of seedlings in raw fish are a major technical difficulty in artificial breeding of raw fish. Locally, it is generally reported that "raw fish require easy fry and breeding is difficult." The highest survival rate is only 50-60%, generally 20-30%, even lower. Therefore, raising the survival rate of raw fish culture and reducing the production cost is a technical difficulty urgently needed to be solved in raw fish breeding.
(i) Domestication of larvae Newly hatched larvae, with poor physique and poor mobility, float on the water or lie on the side of aquatic plants and other attachments, and use their own yolk as a nutrient source. As the yolk sac gradually absorbs and shrinks, larval development continues. Perfection, this is the peak period of death of raw fish seedlings, must be meticulous domestication.
The domestication method is as follows:
1. Timely feeding When the fry hatches for 4-5 days, the yolk sac disappears, and when it starts to feed from the outside, planktonic nets are used to collect zooplankton and filtered through a 30-40 mesh screen (fish hatching requires 2-3 days of filtration), With its filtrate evenly spilled in the hatching tank, if the food can not meet its needs, you can feed the cooked egg yolk, yeast, fish mash and full-price compound feed (powder) as supplementary feed, so that it can eat and eat well. Meet the growth needs of fry.
2. After keeping the fresh water of the fish, the large number of egg membranes and oil-like substances float in the water or sink to the bottom of the water, so it should always maintain a certain micro-water flow to increase dissolved oxygen in the water and eliminate egg membranes and oily substances.
3. Pay attention to the disease prevention and control of raw fish during the seedling stage, which is most susceptible to watery mildew. Usually, 1 to 2 PPM methylene blue or 15 to 20 PPM formalin Quanchiposa is used for prevention. The daily new water should be replaced with 25PPM lime or water in the storage tank. Chlorine disinfectant treatment can be used only after harmless, and it is better to cultivate the pond water into tender green. The fry is reared for 8-10 days, and the body length can reach 10-15 mm, and the body color turns yellow. As the individual fry grows and its density increases, the demand for bait and dissolved oxygen also increases. At this point, the pool should be transferred to seedlings in a timely manner.
(B) Fish Breeding
Pool cultivation
1. 1 The fry pool requires that the raw fish fry be cultivated with earthen ponds. The area is generally 0.2-0.4 mu, and the water depth is 0.5-1.0 meters. Before the fry are released, they must be disinfected by Qingchi; first drain the pool and water, and then use 70 kg of lime to clear the pond per acre (the depth of the pool is 7-10 cm), and apply sufficient water to increase the fertilizer of basal fertilizer. Apply photosynthetic bacteria and other microorganisms. The agent regulates the quality of the water and allows the fish to have a good environment and a sufficient amount of basic food after going down the pond.
1. 2 Before putting fry released fry, put 20-30 fishes first to observe whether the water body has disappeared. The water temperature difference when releasing seedlings can not exceed 2°C, and the stocking density depends on the bait, breeding techniques and breeding specifications, and the general stocking density is 60,000-70,000. Afterwards, the growth and cultivation time of the fry are gradually screened and diluted. There are also 4 to 50 thousand tails/mu at a time, which are directly cultivated into standard fish species.
1.3 Feeding domesticated larvae into feed, the plankton feeds in the lower pool, and as the fry grows, the food intake increases, and the zooplankton in the pool gradually decreases. On the one hand, plankton is cultivated by continuing fertilization. On the one hand, soybean milk, egg yolk, yeast and full-price compound feed (powder) can be added and fed. After 15-20 days of cultivation, when the fish body reaches 3 cm or more, its diet begins to transform and the food intake further increases. Relying on zooplankton can no longer meet its growth needs, then you can feed the fish on the table to tame the food, add 2-3 days later puffed fish fry open feed mixed with fish, then gradually increase the proportion of feed to reduce the amount of fish until It is mainly fed with extruded feed (above 90%), and domestication can usually be completed within 3-5 days.
1.4 Cultivating Management
1) Adjust water quality in time: During the fry breeding process, due to fertilization and feeding, the fecal residue bait is most likely to spoil the water quality. Therefore, during the cultivation of raw fish, water is frequently changed depending on the water quality. Each time the amount of water is changed is 1/4 of the pool water. - 1/3, after the first row of irrigation. In addition, aquatic plants such as water hyacinths or water hyacinths are transplanted in the fish ponds to purify the water quality and conceal the fry.
2) Timely stocking: When there is a big difference in the growth specifications of the fry, the raw fish has a habit of eating big, especially when the food is lacking. Therefore, raw fish fry culture must be timely retraced, sifted, and bred, and the fish in the same pool should strive to be the same size, so as to avoid the weak meat and strong food, affecting the survival rate of fry.
3) Prevent disease and escape: Pay attention to the entrance and exit gates on a daily basis and prevent flooding in rainy days. Pulling the net to screen will inevitably damage the fish body. Once the fish body is injured, it is most likely to suffer from hydromycosis. The production of commonly used malachite green prevention and treatment of 0.1-0.2PPM. Should pay attention to the prevention of trichoderma, slug invasion.
2. Cage cultivation seed
2. 1 Production and setting of cages Net cages are made of 30-40 mesh nylon mesh, 5 meters in length, 1.2 meters in size, rectangular and open. The cage is framed by wood or bamboo. The four corners of the cage are fixed on the frame. It is 30 cm above the water surface, and the net is more than 50 cm above the ground. The pebbles are used as sinks to allow the nets to fully open freely and rise and fall freely with the water level. The spacing between the boxes is 4 to 5 meters, which facilitates the exchange of water bodies inside and outside the tank. The water volume set in the cages must have a certain degree of fatness, be close to the inlet, and be more than 3 meters away from the bank.
2. 2 Fry stocking and feeding fry, must be the same source, the same batch, size and size are basically the same, the general stocking density is 1000-1500/m2.
2. 3 Baits After feeding the domesticated larvae into the cages, they start to attract fish with fish gills. After 2-3 days, they are added with squid mix and fed into a group. After 15 to 20 days of fry feeding, the body length can reach 2 cm or more. At this time, the fish can be fed with puffed fish fry (mixed with a little fresh chilled fish paste) and fed once a day in the morning, in the evening, and once in the day. Feeding amount is 6-8% of fish's body weight.
2.4 Feeding Management
1) Keep the water in the box fresh: After the fish are put out of the box, clean the cage every day and move the position to facilitate convection exchange between the inside and outside of the tank. At the same time, aquatic plants such as water hyacinths or water lettuces, which account for one-fifth of the surface of the water, are put into cages to purify the water and conceal fish seedlings.
2) Timely binning: Fry will be reared within 15 to 25 days in the cage. The individual size will be different and must be sieved and diluted to keep the size of the fry within the cage consistent.
3) Daily management: It is mainly to wash the cages and check whether the cabinets are damaged to prevent escape. Observe the feeding and activities of the fry, adjust the feeding amount and prevent fish diseases.
3. Precautions during fry cultivation During the cultivation of seedlings, it is necessary to observe the activities of the fry, and if it is found that the seed wanders around the edge of the pool, it indicates that the food in the pool is insufficient and should be fed in time. Due to the highly clustered habit of fish in 3 weeks, the fish fry together and fish in the center of the group and frail when feeding. The chance of obtaining food is relatively small, resulting in a total length of 3.5-3.8 cm for fry. Frailty is only 2.3-2.7 cm. It may even cause particularly fragile fish to die due to lack of necessary nutrients. Therefore, one must be fed with sufficient feed, and the other is to improve the feeding method and adopt multiple feedings a day so that the fry can feed evenly and the growth rate is basically the same. In the early stages of cultivation, the lack of rotifers and leeches, the lack of silkworms, small fish, and small shrimps in the middle and late stages all caused the inequality in the ingestion of the seedlings to cause mixed growth and triggered killing each other. Therefore, when the natural pond feed is insufficient, light can be set on the surface of the pond to attract insects for the consumption of fish fry, and water canals, chilled fish paste and squid can also be fed with the powder. The raw fish fry have cluster habits. If the clusters are found to be too large, they should be evacuated in time. Especially in the hot and humid nights, if the above phenomenon occurs, the fish fry should be picked up at other places in the nursery pond. Pay attention to changes in the water color, especially in the hot season, if the water quality is too fat, the dissolved oxygen is insufficient, which can cause the fry floating head and flooding ponds, causing a large number of deaths of the seedlings. Therefore, it is necessary to inject new water in a timely manner according to the growth conditions of the seed, gradually increase the water level, adjust the water quality, and increase the spatial adjustment of the seedling density of the water body.

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