Artificial culture technology of crayfish

Crayfish, scientific name Procambarus clarkii, also known as crayfish, red swamp crayfish, belong to Arthropoda, crustacea, Decapoda, Crayfish suborder, Crustaceae, Procambarus. Originally from North America, it was introduced to Japan by the United States in 1918 and China in 1929. Now it is mainly distributed in the middle and lower reaches of the Yangtze River. In recent years, the shrimp has been a hot market, the price is rising, supply exceeds demand, and the development prospect is broad.

Breeding prospect

Procambarus clarkii has strong adaptability to the environment, less diseases, tolerance to hypoxia, can grow and breed in ponds, ditches, lakes, rice fields, marshes and other water bodies, and can leave water or live in caves for a long time, and has strong tolerance to adverse environment. Transport is convenient and the transport survival rate is high. This is unmatched by other shrimps. At the same time, Procambarus clarkii seedlings are easy to breed, can be self-propagated and self-bred, without complex equipment, the technology is simple, the feed is easy to solve, and is suitable for artificial breeding. Generally, the yield of intensive farming in ponds is 400kg per mu and the profit is more than 1600 yuan.

Market prospect

At present, the artificial culture of Procambarus clarkii is small, which mainly depends on natural fishing, and its natural resources can not meet the consumption demand of international and domestic market. Europe and the United States are the main consumers of Procambarus clarkii. In the United States, the shrimp is not only an important edible shrimp, but also an important bait for fishing, with an annual consumption of 60 ~ 80,000 tons and a self-sufficient capacity of less than 1 inch. The European Union and the United States import 20,000 tons of crayfish from China every year. Sweden is an avid consumer of crayfish. Every year, Sweden holds a three-week crayfish festival, the whole country not only eats crayfish, but also people draw crayfish patterns on tableware and clothes. Sweden imports 5-100000 tons of crayfish every year. Western European markets consume 60-80,000 tons of crayfish a year, while Western Europe accounts for only 20% of the total consumption.

In recent years, the domestic consumption of Procambarus clarkii has increased sharply, and it has become a home-cooked dish for most families in urban and rural areas. In Wuhan, Nanjing, Shanghai, Changzhou, Wuxi, Suzhou, Huai'an, Hefei and other large and medium-sized cities, annual consumption is more than 10,000 tons. In these large and medium-sized cities, the sales volume of Procambarus clarkii in restaurants and stalls in one night is about 15000 kilograms. According to relevant information, there are more than 30 restaurants and stalls selling more than 150 kilograms of crayfish every night in Hefei, more than 100 selling 50 kilograms every night, and countless stalls selling 10 to 20 kilograms every night. From June to September every year in Nanjing, the daily consumption of crayfish reaches 7080 tons. Judging from the current consumption level, there is a great gap in crayfish at home and abroad, and there is a great way to develop artificial culture.

Processing prospect

The original crayfish meat is delicious and nutritious, with a protein content of 16%-20%. The protein content of dried shrimp is more than 50%, which is higher than that of ordinary fish and exceeds the protein content of eggs. The contents of trace elements such as zinc, iodine and selenium in shrimp meat are also higher than those in other foods, and the muscle fiber is delicate and easy for human body to digest and absorb. Moreover, the meat yield of the shrimp is about 20%, and it can process shrimp meat and shrimp tail, and the industrial raw materials such as chitin, chitin and chitin extracted from the shell are widely used in agriculture, food, medicine, tobacco, paper making, printing and dyeing, daily chemical and other fields, with great potential for value-added processing.

Morphological characteristics

Crayfish are stout, thick carapace and crimson. The body is covered with a sharp and hard chitin shell, the body consists of 21 segments of the head, chest and abdomen, the head and chest is slightly larger, the head has 3 pairs of tentacles, the tentacles are thick near the head, and the tip is small and pointed. There are 5 pairs of steps in the chest, the ends of 1-3 pairs of feet are clamp-shaped, and the ends of 4-5 pairs of feet are claw-shaped. The second pair of foot is particularly developed into a large claw, and the claw of male shrimp is more developed than that of female shrimp. There are five powerful tail fans in the tail of crayfish. Female shrimp bend inward during egg holding and incubation period-crawling or attacked by enemies to protect fertilized eggs or young shrimp from damage.

Life habits

Crayfish do not have strict requirements on the water environment. Crayfish can survive in water with a pH of 5.8 ~ 8.2, a temperature of-15 ℃ ~ 40 ℃ and dissolved oxygen of no less than 1.5mg / L, and can survive the winter naturally in most areas of our country. The most suitable water body for crayfish growth is pH 7.5-8.2, dissolved oxygen 3 mg / L, and water temperature 20-30 ℃.

Crayfish like warm and afraid of light, have obvious phenomenon of vertical movement day and night, when the light is strong, they sink into the water or hide in the cave, when the light is weak or dark, they begin to move, and usually hold the aquatic plants or suspended objects in the water to lie on their side on the surface of the water, and have the habit of digging holes, the depth of which is 50cm to 80cm.

Food habit

Crayfish are omnivorous animals, a variety of fresh aquatic plants, benthos, molluscs, large zooplankton, fish and shrimp carcasses and similar carcasses are their favorite food, artificial feed is also very fond of eating. After molting for the first time, the larvae began to feed on phytoplankton, small cladocera larvae, rotifers and so on. Crayfish are gluttonous and cannibalize each other when there is not enough bait. Soft-shell shrimps that are molting or just molting are the most likely to be eaten.

Reproductive habit

Crayfish spawn many times a year and mature sexually at the age of 9-12 months in the natural environment. The weight of sexually mature individuals is generally 30 million 100g. The mating season is generally from late April to July, and the peak of group mating is in May. It can lay eggs 3 to 4 times a year, with 300 eggs laid each time. The female shrimp carries out reproductive molting before mating, and the molting process can be completed in about 2 minutes. When mating, the female shrimp lies on the water on its back, the male shrimp clamps the female's front claw with the chelate foot, and the mating device is inserted into the female body. The mating time is 10-30 minutes. From 3 to 10 hours after mating, the female shrimp begins to lay eggs, and the fertilized eggs adhere to the abdominal limbs for development. The length of embryonic development is closely related to the water temperature, the higher the water temperature is, the shorter the hatching time is, and the lower the water temperature is, the longer the hatching time is. The larvae are usually hatched after 5-8 weeks.

Molting and growth

Crayfish achieve weight and length growth by molting. After molting, the new shell hardens after 12 hours. Molting is closely related to water temperature, nutrition and ontogeny. The larvae usually molt once every 4 or 6 days. If the water temperature is high and the food is adequate, the molting interval is short. Under the condition of suitable water temperature and sufficient feed, the shrimp seedlings can reach 8 cm in length, 15 g in weight and more than 30 g in weight after 3 to 4 months of growth.