The Procambarus clarkii, commonly known as lobster, is known for its delicious taste and rich nutrition, and is increasingly known and consumed in large quantities. Astaxanthin, chitin, and its derivatives extracted from its crustaceans are widely used. It has been used in food, medicine, feed, agriculture, and environmental protection, etc. In recent years, it has not only become a best-selling aquatic product in China, but also its shrimp, shrimp yellow, and whole shrimp exports have increased rapidly. A great deal of fishing has caused the natural resources of the crayfish crayfish to decrease year by year, so it is of great significance to carry out artificial breeding to meet the growing domestic and international demand, as well as the protection and development of resources.
Biological characteristics of a crayfish
1.1 Morphological characteristics Crawfish crustacean crustaceans, adult shrimp body length of 70 to 130 mm (eye to tail fan distance), stout type, deep crustacean. The body of the shrimp was divided into two parts: chest and abdomen. There were 5 pairs of appendages on the head. Among them, 2 pairs of tentacles were well developed, with attached appendages on the chest, followed by 5 pairs of stepped feet, and the first 3 pairs of stepped feet all had chelation. The first pair was particularly developed. , similar to the chela of crabs, especially males. The abdomen is short, with 6 pairs of appendages. The first 5 pairs are swimming legs. They are underdeveloped. The end pair is the tail. The tail section is combined with the tail section and the tail fan is developed. Females of the same age are larger than males. Males on the inside of the second abdominal foot had l-barreled male appendages, while females did not have this pair of appendages. This is another major feature in recognizing male and female crayfish.
1.2 Inhabitation habits Crawfish clams are afraid of light. When the light is weak or dark, they climb out of the cave. They usually cling to the water plants or suspended matter in the water. They are “sleepingâ€. When the light is strong, it sinks into the bottom of the water or hides in the cave. It has obvious phenomena of day and night vertical movement.
1.3 Ingestion Habits Cuckoos are eaten raw, plant foods and animal foods can be eaten, the former mainly. Plant-type diets include plant stalks and aquatic plants, and animal diets include crushed snails, small trash fish, and animal organs. Insufficient food - or groups are too large, the crayfish crustaceans often eat each other, eat prawns shrimp, shell hard to eat soft shell, so it is the most likely to be the skin during the fur and hide - skin after a long period of time Residual food. Insufficient food will also cause the crayfish to escape from the pond. The crayfish crayfish - like to feed on the water bottom and more at night, the optimum temperature for feeding is 25 °C - 30 °C, the water temperature below 8 °C or more than 35 °C feeding significantly reduced.
1.4 Breeding characteristics Crawfish crayfish can lay eggs 3 to 4 times a year. From mid-April to early May, when the water temperature is 15°C or more, sexually mature females begin to genital molting, and the entire molting process can be completed in about 2 minutes. The male and female shrimps on the abdomen were relatively mated after mating and the mating time lasted for about 5 minutes. After 3-10 hours of mating, the females hold eggs and the eggs are yellow in color. The amount of eggs held varies with the size of the broodstock. Individuals hold more eggs and smaller individuals hold fewer eggs, ranging from 500 to 2,000 grains. During the spawning of females, the first pair of stepped feet often stretches between the egg pieces to remove impurities and necrotic eggs, and the swimming feet often swing to drive the water to obtain sufficient oxygen for the eggs. Egg hatching is related to water quality, dissolved oxygen, transparency and other water quality factors. The higher the water temperature below 35°C, the shorter the incubation period, which generally takes about ll-15 days. After hatching, the eggs develop into juvenile shrimp. The l-tailed broodstock eventually has about 50-200 tails, that is, the survival rate is about 10%. After the juveniles are detached from their mothers, they quickly enter the first molting process. After each molting process, the growth rate of the juveniles is significantly accelerated. Generally, the development of adult shrimps requires more than four molting processes.
2 Eco-index of normal growth and development of crayfish The water body is the living environment of crayfish. The quality of water directly affects the health and development of crayfish, and good water conditions can promote the normal development of shrimp. The test results showed that the minimum requirement for dissolved oxygen in healthy growth of Crayfish was 3 mg/l, the suitable pH range of the water was between 7.5 and 8.5, and the water transparency below 20 cm and above 25 cm. The growth and development of crayfish will be affected to varying degrees.
3 The main techniques of fish and shrimp polyculture
3.1 Feeding of fish and shrimps We used the fish-shrimp polyculture test on the surface of aquaculture farms in Xintuan Town, Dafeng City. The test pool was a standard fish pond of 5 mu in both of them. In February 1996, we put grass, alfalfa, pupa, etc. in each mu. 5000 fish fry, and then distributed two groups of crawfish crayfish: the first group for the end of April to put a specification of 20-30 tail / kg 40 kg of brooding broodstock, the second group for the end of May to put 100 to 120 / Kilograms of prawns 80 kilograms.
3.2 Pond treatment Prior to Sheung Shui disinfection and sterilization of 10-15 kg of lime per acre, aquaculture process monitoring and control of relevant water quality indicators, according to the water quality and the incidence of fish and shrimp with 0.2-0.4 mg / elevated potassium manganate or quicklime disinfection. Taking into account the clyster of the crayfish, it is best to plant forages such as peanuts and ryegrass at the edge of the pond, and to stock up with water hyacinth and water peanuts on the water surface. This will also facilitate the feeding, molting and breeding of the crawfish crayfish - etc. Activities and reduce their mutual killings.
3.3 The feeding of fish and fish polyculture, both to consider the feeding characteristics of shrimp, but also take into account the fish's demand for bait. In the experiment, we fed 250 kg of semi-rotated barley, wheat, broad bean and other crop straws or 10,000 kg of fresh water grass as coarse material per acre of water surface. The amount of concentrating material is slightly higher than that of the pure fish with the same density. It is generally controlled at about 350 kg/mu. The ratio of ingredients is 27% for fishmeal, 18% for yeast, 25% for soybean meal, and 15% for barley. 15% wheat flour.
3.4 Fishing period of fish and shrimp In order to obtain higher aquaculture efficiency, the fishing period of the crayfish should be determined according to market demand and shrimp size. Usually in July and July, shrimps are used for fishing, large-scale listings, and small ponds are put back into the pond. This will last until the end of October. The fish fishing is arranged around the New Year's Day and the Spring Festival next year.
3.5 Relationship between benefit and stocking density As of the end of October 1996, the first group cumulatively captured 393 kg/mu of shrimp, 152 kg/mu of adult fish, and the second group accumulated 400 kg of shrimp. / Mu, adult fish 147 kg /-mu, no significant difference between the two groups of results. Calculated according to the actual sales results, the mu benefits reached 2,500 yuan, a net increase of nearly 1,000 yuan compared with pure intensive fish. The fish and shrimp stocking densities vary with stocking time. In actual application, depending on the individual size of fish and shrimp, taking into account the characteristics of multiple breeding and rapid growth of Klebsiella maxima, higher benefits can be obtained.
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