River crab breeding technology
2018-06-07 10:01:29
Also known as hairy crabs, crabs, and the scientific name of Chinese velvet crabs, they often live in fresh waters and rich aquatic plants. They have the characteristics of nocturnal emission. They usually come out to feed at night. Every year from June to September is the peak period of feeding crab activities. Big-water-surfaced crabs have the advantages of smooth water flow, large wind surface, sufficient dissolved oxygen, and abundant natural bait resources. Therefore, the use of big-water-surfaced crabs can significantly reduce production costs and improve aquaculture efficiency. Now combining the years of farming experience in my town, the technical points are summarized as follows.
1 Preparation before stocking
1.1 Selection of water area According to the biological characteristics of river crabs, fresh water should be selected, sunlight should be sufficient, and aquatic plants should be abundant (preferably submersed plants such as Vallisneria, black-leaf algae, etc., reeds and rushes in emerged plants).蚬 More waters (inadequate snails can be stocked artificially). In this way, river crabs can obtain sufficient animal and plant foods, which are conducive to satisfying and promoting the growth of river crabs. Where there are not many plants, some plants can be used to make up for it.
1.2 The establishment of anti-escape facilities uses nets and stumps (bamboo piles) to enclose aquaculture waters. Barriers should be made of polyethylene mesh. It is advisable that the mesh size is suitable for avoiding crabs. It is best to use double-layered fences. The height of the block should be more than 1 meter above the average annual water level. The foot of the net is used as a sink for sinking into the sediment, and the net is inserted into the soil with a barbed pile. The inner net is made of plastic film or calcium plastic plate to prevent the crab from pulling out of the net. Escape. At a certain distance, trees (bamboo) piles are used to insert 0.5-1.0 meters into the soil to reinforce the block and prevent storm surges.
1.3 Before the wild young crabs are stocked, various methods should be used in advance to remove the wild fish in the waters, reduce the natural enemies of the crabs, and provide suitable breeding environment for the crabs.
2 Crab species stocking
2.1 Strictly control the quality of rearing crabs, and the importance of seedlings. Pay attention to the following points when purchasing seedlings.
2.1.1 The optional juvenile crab (crab species) should be neatly sized, robust, and free from disease and injury. This is the first and most basic condition.
2.1.2 In Yangtze River and Huaihe River valleys and Yangtze River basin, Yangtze River Crab is the preferred species for purchasing crabs. Its growth rate and catch rate are better than other crab species. Under the same conditions, the sexual maturity of Liaohe crab is earlier than that of Changjiang crab. The average size of the individuals is naturally much smaller.
2.1.3 Crab species cultivated from inland freshwater are superior to those cultivated in coastal areas. In general, the cultivation of water in the coastal areas has a certain degree of salinity. The cultivated crab seedlings do not adapt to inland waters and are easy to ripen. The growth rate is not very satisfactory. Therefore, it is better to cultivate young crabs if possible.
2.1.4 From the results of breeding for many years, the ecological soil pond nursery is better than the factory cement tank nursery. The former cultivated seeds are more suitable for natural stocking, especially for large water surface stocking.
2.2 Timely establishment of stocking time Water stocking should be based on winter and spring, and December and March of the following year are the best stocking seasons. In cold winters and icings, it is generally not appropriate for stocking. Frostbite crab species affect the survival rate.
2.3 Determine the reasonable amount of stocking The amount of stocking should be determined based on the natural food in the water area and its own economic power. 200-300 birds per kilogram were stocked at a density of 400-600 per 667 square meters. Areas with large areas, adequate feed, good water quality, and guaranteed funds can also be appropriately increased, but should not exceed the natural feeding capacity of the water area.
2.4 Before stocking with scientific stocking methods, the crabs should be placed on a ship and should be placed as evenly as possible and with a larger range. If it is a crab species purchased from other countries, it will not be suitable to put it directly after long-distance transportation and longer dewatering time. The juvenile crabs should be first treated with slow seedlings, that is, they should be soaked in water for 1-2 minutes together with net bags, and they should be taken out. 3-5 minutes, so repeated 2-3 times, until the young crab fully absorb water, adapt to the water environment and then stocked by the above method.
3 Feeding management
3.1 The feeding of bait on large waters is generally more abundant. In the early period, it is generally not necessary to feed. In July to September, it is a period of vigorous growth of crabs. In order to effectively protect aquatic plants from massive damage, some artificial baits should be fed in time. Such as snails, river clams, fish and shrimp, cereals, beans, pumpkin silk, hawthorn silk, etc. in plant foods to better promote the rapid growth of crabs. Feeding is usually 2 times a day, 8-9 hours in the morning and 1-18 hours in the afternoon, and the daily feeding amount should be 5%-7% of the crab body weight. It should be fed in the deep water area of ​​aquatic plants in the morning and in the shallow water area of ​​aquatic plants in the afternoon.
3.2 Water Quality Management In general, the water bodies are generally open and the water quality is not easily deteriorated, but they should be removed in time when the water grass is bitten by floating crabs to avoid deterioration of the water quality in the hot season. At the same time, organic phosphorus and pyrethroids are prohibited from polluting the water quality. In addition, 25-30 kg/667 square meters of hydrated water is splashed with lime every 15 days to improve water quality.
3.3 Day-to-day management First of all, it is necessary to strengthen the management of the block and timely check whether there are loopholes in the mesh of the fence. If loopholes are found, repairs should be made in time. Especially during the flood season, crabs easily escape with the flow of water. In addition, during the growth of crabs, the prohibition of salvaging aquatic animals, prohibiting the release of ducks, and prohibiting the use of fishing gear for underwater operations, are very likely to cause river crab casualties, especially during the peak period of crab shells, which is more harmful.
4 Disease Prevention and Control
4.1 Disinfection of water clear ponds should be carried out as far as possible.
4.2 Actions should be light and fast during operation. Try not to injure crabs.
4.3 The use of regular lime splashing and bait feeding with internal medicine combined to minimize the occurrence of disease. Common internal medicines include norfloxacin, heparin, and FRC.
5 Crab-harvesting Crab-farming crabs are different from crabs in ponds and should be harvested in due course. Since mid-September, a considerable number of crabs have attempted to climb out of the net. It is therefore important to determine the timing of the fishing time in order to increase the recovery rate and reduce crab escape. Therefore, large water surface block crabs, must be opened in advance to catch, generally selected in early September, catching crabs in the natural reproduction before the concentration of forces to organize fishing, usually using cages and crabs (Ecstasy) fixed set arrest, fishing effect is good .
1 Preparation before stocking
1.1 Selection of water area According to the biological characteristics of river crabs, fresh water should be selected, sunlight should be sufficient, and aquatic plants should be abundant (preferably submersed plants such as Vallisneria, black-leaf algae, etc., reeds and rushes in emerged plants).蚬 More waters (inadequate snails can be stocked artificially). In this way, river crabs can obtain sufficient animal and plant foods, which are conducive to satisfying and promoting the growth of river crabs. Where there are not many plants, some plants can be used to make up for it.
1.2 The establishment of anti-escape facilities uses nets and stumps (bamboo piles) to enclose aquaculture waters. Barriers should be made of polyethylene mesh. It is advisable that the mesh size is suitable for avoiding crabs. It is best to use double-layered fences. The height of the block should be more than 1 meter above the average annual water level. The foot of the net is used as a sink for sinking into the sediment, and the net is inserted into the soil with a barbed pile. The inner net is made of plastic film or calcium plastic plate to prevent the crab from pulling out of the net. Escape. At a certain distance, trees (bamboo) piles are used to insert 0.5-1.0 meters into the soil to reinforce the block and prevent storm surges.
1.3 Before the wild young crabs are stocked, various methods should be used in advance to remove the wild fish in the waters, reduce the natural enemies of the crabs, and provide suitable breeding environment for the crabs.
2 Crab species stocking
2.1 Strictly control the quality of rearing crabs, and the importance of seedlings. Pay attention to the following points when purchasing seedlings.
2.1.1 The optional juvenile crab (crab species) should be neatly sized, robust, and free from disease and injury. This is the first and most basic condition.
2.1.2 In Yangtze River and Huaihe River valleys and Yangtze River basin, Yangtze River Crab is the preferred species for purchasing crabs. Its growth rate and catch rate are better than other crab species. Under the same conditions, the sexual maturity of Liaohe crab is earlier than that of Changjiang crab. The average size of the individuals is naturally much smaller.
2.1.3 Crab species cultivated from inland freshwater are superior to those cultivated in coastal areas. In general, the cultivation of water in the coastal areas has a certain degree of salinity. The cultivated crab seedlings do not adapt to inland waters and are easy to ripen. The growth rate is not very satisfactory. Therefore, it is better to cultivate young crabs if possible.
2.1.4 From the results of breeding for many years, the ecological soil pond nursery is better than the factory cement tank nursery. The former cultivated seeds are more suitable for natural stocking, especially for large water surface stocking.
2.2 Timely establishment of stocking time Water stocking should be based on winter and spring, and December and March of the following year are the best stocking seasons. In cold winters and icings, it is generally not appropriate for stocking. Frostbite crab species affect the survival rate.
2.3 Determine the reasonable amount of stocking The amount of stocking should be determined based on the natural food in the water area and its own economic power. 200-300 birds per kilogram were stocked at a density of 400-600 per 667 square meters. Areas with large areas, adequate feed, good water quality, and guaranteed funds can also be appropriately increased, but should not exceed the natural feeding capacity of the water area.
2.4 Before stocking with scientific stocking methods, the crabs should be placed on a ship and should be placed as evenly as possible and with a larger range. If it is a crab species purchased from other countries, it will not be suitable to put it directly after long-distance transportation and longer dewatering time. The juvenile crabs should be first treated with slow seedlings, that is, they should be soaked in water for 1-2 minutes together with net bags, and they should be taken out. 3-5 minutes, so repeated 2-3 times, until the young crab fully absorb water, adapt to the water environment and then stocked by the above method.
3 Feeding management
3.1 The feeding of bait on large waters is generally more abundant. In the early period, it is generally not necessary to feed. In July to September, it is a period of vigorous growth of crabs. In order to effectively protect aquatic plants from massive damage, some artificial baits should be fed in time. Such as snails, river clams, fish and shrimp, cereals, beans, pumpkin silk, hawthorn silk, etc. in plant foods to better promote the rapid growth of crabs. Feeding is usually 2 times a day, 8-9 hours in the morning and 1-18 hours in the afternoon, and the daily feeding amount should be 5%-7% of the crab body weight. It should be fed in the deep water area of ​​aquatic plants in the morning and in the shallow water area of ​​aquatic plants in the afternoon.
3.2 Water Quality Management In general, the water bodies are generally open and the water quality is not easily deteriorated, but they should be removed in time when the water grass is bitten by floating crabs to avoid deterioration of the water quality in the hot season. At the same time, organic phosphorus and pyrethroids are prohibited from polluting the water quality. In addition, 25-30 kg/667 square meters of hydrated water is splashed with lime every 15 days to improve water quality.
3.3 Day-to-day management First of all, it is necessary to strengthen the management of the block and timely check whether there are loopholes in the mesh of the fence. If loopholes are found, repairs should be made in time. Especially during the flood season, crabs easily escape with the flow of water. In addition, during the growth of crabs, the prohibition of salvaging aquatic animals, prohibiting the release of ducks, and prohibiting the use of fishing gear for underwater operations, are very likely to cause river crab casualties, especially during the peak period of crab shells, which is more harmful.
4 Disease Prevention and Control
4.1 Disinfection of water clear ponds should be carried out as far as possible.
4.2 Actions should be light and fast during operation. Try not to injure crabs.
4.3 The use of regular lime splashing and bait feeding with internal medicine combined to minimize the occurrence of disease. Common internal medicines include norfloxacin, heparin, and FRC.
5 Crab-harvesting Crab-farming crabs are different from crabs in ponds and should be harvested in due course. Since mid-September, a considerable number of crabs have attempted to climb out of the net. It is therefore important to determine the timing of the fishing time in order to increase the recovery rate and reduce crab escape. Therefore, large water surface block crabs, must be opened in advance to catch, generally selected in early September, catching crabs in the natural reproduction before the concentration of forces to organize fishing, usually using cages and crabs (Ecstasy) fixed set arrest, fishing effect is good .