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1. Broodstock requirements: Select broodstock to require good vigor, complete appendages, smooth body, no attachments, and diseases (such as tail rot and shell damage) for broodstock. In order to achieve high fertility, we must choose giant crawfish with a body length of 9 cm or more, good maturity, and high spawning power. In addition, we must group them according to their size and select the males that match them. An easy method of determining the ovary has been developed to eliminate the problem that the red clams do not lay eggs in the short term. This method is a clear film from the head and tail of the red clam crayfish, illuminated with strong light, observing the body cavity, such as the female without any sign of ovarian development, it may take several weeks or months to reach sexual maturity, Red-living crayfish, which are clearly visible in the ovaries, generally lay eggs within 4 weeks.
2. Identification of male and female: The male individuals of red-spotted crayfish of the same age are larger than females, and there is a bright red flexible membrane plaque on the outer side of the two chewing feet of the male adult shrimp, and the appearance is easily distinguishable from the female.
3. Male to female ratio: Under natural breeding conditions, the proportion of males and females is similar to Macrobrachium rosenbergii, but slightly more females are required. In the breeding process, the ratio of male to female is more suitable for 2:1.
4. When the broodstock began to be cultured: Although the survival temperature range of the red snapper is wider than that of the giant Roche shrimp, if the broodstock begins to be cultivated too late and the water temperature is lower than 11°C, there will be a large number of broodstock deaths. Practice has shown that before the end of November in eastern China, the cultivation of quail areas began before the beginning of December.
Second, broodstock cultivating shrimp grown in earthen ponds, before entering the wintering pool, must be formalin concentration of 20010-6 bath for about 10 minutes, eliminate attached organisms before they can move into the broodstock pool culture. The broodstock is a very important material basis for the artificial propagation of red-caught crayfish. Because of the small amount of eggs that the shrimp can hold, there must be a large-scale source of shrimps for mass production. Therefore, adopting suitable breeding and management methods to increase the survival rate of broodstock is the primary task of artificial breeding.
1. Cultivation pond: The broodstock cultivation pond is the living environment of the broodstock, and the quality of the cultivation pond directly affects the growth and development of the broodstock. According to the specific conditions of production now, there are mainly two kinds of cultivation ponds, one is the cement pool and the other is the earth pool. The choice of a breeding pond must consider the following:
(1) Production scale: According to the scale of production, a suitable broodstock cultivation pond is selected according to the scale of production. However, no matter the size of the site, its location should be well-water source, convenient drainage and irrigation, fresh air, quiet environment, free from natural and man-made interference.
(2) Area: The area should be adapted to local conditions. Large-scale production is generally more than 80 square meters, and it can even be 2,000 square meters or more. The water body is large and the water quality is relatively stable; the small scale production cultivation pond can be several to ten square meters.
(3) Depth of water: Generally 50 to 60 centimeters. During the wintering period, especially the soil in the earthen pond should be deepened, which is beneficial to the constant water temperature and reduce the waste of energy.
(4) Water Quality: The general requirement is that the water quality should be fresh and the dissolved oxygen should be high. Especially during the intensive cultivation, the dissolved oxygen requirement is above 4 mg/L. The temperature during the winter should be controlled at 16-18 °C.
(5) Concealed objects and escape prevention facilities: In order to reduce the fratricidal phenomenon of broodstock, bamboo baskets, hanging nets, bamboos and other concealed objects are added in high-density breeding ponds. Since the broodstock during the wintering in the earthen pond is easy to make holes, the best way is to add cement to the slope of the pool, and use a plastic film around the dyke to stop the escape wall with a height of 30 cm. 2. Restocking of broodstock: Before broodstock is stocked, the cement pool should be cleaned and disinfected. The earthen pond should be cleared of silt, dirt and residual feeding, and the loopholes must be repaired to prevent escape, drainage, irrigation and heat preservation facilities. Before the broodstock enters the pool, it is necessary to disinfect the pool water with quicklime or bleaching powder, and then stock the broodstock. The density of stocking is directly related to the breeding effect of the broodstock. If the stocking density is too large, the growth and development of the broodstock will be poor. If the stocking density is too small, the pool, manpower and material resources will be wasted. Generally depending on the area of ​​the pool, the breeding season, the physiology of the broodstock and the size of the individual determines its stocking density. According to the practical experience in production, there can be a specification of about 20 shrimps per kilogram of water per cubic gram of water.
3. Cultivation and management of broodstock: Since broodstock have a small amount of eggs, it is necessary to increase the survival rate of broodstock during the cultivation process in order to ensure the production of seed production. In cultivation and management, we must maintain good water quality, rich nutrition, adequate oxygen and suitable temperature, and good anti-escape facilities.
Good water quality makes the broodstock have a very good living environment. Generally, water and drainage should be added depending on the color, transparency and weather conditions. Change the water once every 3 to 4 days, change the water of the pool one third at a time to ensure good water quality. Nutrients are the material basis for gonads development in broodstock. In addition to putting in a small amount of aquatic plants (such as water hyacinth) in the pond, they are usually cultivated at early stage and are generally fed with shrimp and crab pellets with high protein content. In places where conditions are favorable, especially in the process of warming and strengthening cultivation, increasing the feeding of animal feeds such as small-sized trash fish, cockroaches, silkworm cocoons and shellfish will promote its growth and development. The amount fed is generally 4% to 5% of the body weight of the broodstock, and is increased or decreased depending on the feeding condition. Residues must be sucked off regularly to avoid deterioration of water quality. Oxygen can be oxygenated regularly during the overwintering process and must be continuously oxygenated during the process of strengthening management. When culturing and raising temperature, the temperature is controlled at 28 to 30°C. In addition, during the wintering in the earthen pond, it is necessary to do a good job of preventing the escape, because on very cold days, the red crayfish will make holes.
4. Wintering of broodstock: According to reports, the minimum survival temperature of red-claw is 5°C. However, through observation during production, when the water temperature is lower than 9°C, the mortality rate of the 3cm or so shrimp is high during the winter and the adult shrimp can survive, but after 2 to 3 months, there will be a large number of deaths. Therefore, do a good job of broodstock overwintering work to ensure that the water temperature during the winter during the 16 ~ 18 °C, but also an important part of the entire breeding work.
(1) Main facilities for wintering: The method of overwintering of broodstock is the same as that of Macrobrachium rosenbergii. The commonly used methods for overwintering include plastic film covering pool insulation method, electric heater heating method, hot spring water overwinter method, factory residual hot water overwinter method and glass The greenhouse overwintering method can achieve the purpose of safe wintering for broodstock.
(2) Intensive cultivation: Red-claw crayfish can generally hold eggs 2 to 3 times a year, the breeding period is 5 to 6 months, and the peak period is 6 to 8 months. Each shrimp has 40 to 1400 eggs. At this stage, broodstock must be spawned several times for spawning, and each time it is bred, it consumes a large amount of nutrients in the body, and its constitution is significantly weakened. In addition, when hatchlings and broodstock hatch young shrimps, the mother shrimps should be promptly removed from the nursery and fed with enough feed so that sexual maturity can be achieved again. After all the juvenile shrimps were disengaged from the mother shrimps, they began mating and spawning to begin the next breeding process.
Third, after spawning hatching incubation, the gonad gonads mature, in the appropriate temperature conditions (25 ~ 30 °C), began mating and fertilization, and began spawning and fertilized egg hatching.
1. Shrimp maturity and mating spawning
(1) Mature period: shrimps cultivated in the past can reach sexual maturity after feeding and strengthening during the wintering period. Generally, the number of females is 50 to 70 grams and the number of males is 70 to 100 grams. There is a close relationship between the spawning amount of broodstock and the quality of broodstock, the size of the individual, the living environment, cultivation conditions and age. According to reports, the number of eggs in the same size of broodstock in the second year is higher than the number of eggs in the first production.
(2) Mating: In the breeding season, males actively approach the females, head to head, and push the females with the smooth outer edge of the second step until they react. The responding females will actively approach the males. The male raised his head and chest, and his abdomen rolled up. The females continued to move forward until they climbed above the abdomen where the males raised their heads. The male holds the female and adjusts his position. The female runs immediately after ejaculation. The mating time is short, usually only 1 minute. A few minutes after mating, the females disperse the spermatozoa with their feet, and the last couple of steps play a role.
(3) Spawning: Females start spawning 24 hours after mating, and the resulting eggs are tightly wrapped around the abdomen and adhere to the cilia of the abdominal swimmer's foot. It usually takes 24 hours to fertilize and the fertilized egg is hatched in the abdomen of the female. During hatching, the females are not active and are generally hidden in concealed species. A few female eggs are still ingested. At this time, the abdomen eggs of the egg-bearing shrimps are easy to fall off. Therefore, it is necessary to be very careful during operation and management.
2. Incubation conditions:
The eggs that have been fertilized in vitro are left in the abdomen of females and leave the mothers after 42 days of incubation under appropriate conditions. Therefore, the management work at this stage is mainly to meet the ecological conditions required for broodstock and hatching of eggs, among which the requirements for temperature, light, water quality, dissolved oxygen, and bait are more prominent.
(1) Dissolved Oxygen: Oxygen-bearing shrimps have high oxygen consumption. During the incubation period, they must be continuously oxygenated to make dissolved oxygen above 5 mg/l.
(2) Illumination: It has been reported that the reproduction of red-claw crayfish is also affected by light. Generally, light is irradiated for 14 hours and then covered with black cloth to make the pool dark for 10 hours.
(3) Temperature: Control at 26 to 28°C.
(4) Feed for egg-holding shrimp: The feed for egg-holding shrimp must consist of a variety of foods, including fresh aquatic plants. Some animal feeds such as fish and small amounts of shrimps and crabs are fed with high-protein pellet feed. The results will be better. .
3. Hatching (embryo development):
During hatching, hatching shrimp often crawls or inhabits on the belly to protect the fertilized eggs from outside influence and damage. Fertilized eggs embryonic development process (see table), egg color from yellow-green to dark red, after the gradual enlargement of the transparent area, eggs slightly expanded and elongated, eye spots, appendages formed, and finally the egg off, young shrimp formation. However, the yolk has not completely disappeared, and it still depends on the abdomen of the female shrimp. After 7 to 10 days, she left the mother to live independently. At this time, the juvenile shrimp turned pale brown and her body length was 0.8 cm. Like other crustaceans, in the optimum temperature range, the higher the water temperature, the shorter the incubation time. If the water temperature is lower than 20°C in case of low temperature, the range of change will be large, the fertilized egg will easily fall off, or the embryo will die due to the sphaerocephala. The general water temperature is 26 ~ 29 °C, incubation time is 42 ~ 47 days.
Red clam crayfish seed production technology
First, broodstock selection red-handed crayfish can spawn a number of times a year, the length of white fleas has a certain influence on its reproduction. The spawning period usually starts at the late spring and early summer when the daylight is gradually prolonged, but the main influencing factor is the water temperature. There is no spawning phenomenon when the water temperature drops below 20°C. When the water temperature rises from 20°C, mating and oviposition occur gradually. The shrimp is kept well and can be reproduced 2-3 times a year.