Seedling raising of Eriocheir sinensis in greenhouse

Crab breeding is an important link in crab production, and cultivating strong crab seedlings is conducive to high yield and high efficiency of crabs. If the big-eyed larvae of Eriocheir sinensis are directly put into crab crab pond, not only the temperature is low in early spring, but also the crab seedlings can't survive, and they often kill each other for lack of food, resulting in low survival rate. From March to May, it is necessary to build a plastic greenhouse to raise crab seedlings. According to the biological characteristics of young crabs, environmental conditions and sufficient bait are provided for their growth and shelling, and five-stage young crabs with neat specifications, appropriate size and high survival rate are cultivated.

Build a shed and a pool first. Crab seedling pond depends on the number of crabs, generally 0.5- 1 mu. The pool depth is 0.8- 1m, the water depth is 0.4-0.8m, and the pool slope ratio is about 1: 1.5. The water source is abundant, the water quality is good, the bottom of the pool is hard and the ridge of the pool is firm and watertight, and the plane of the pool bottom is inclined to the water outlet. The pond is rectangular and arranged in the east-west direction, with the length-width ratio of 5: 3.

Second, clean the pool for disinfection. Cleaning the pool can kill enemy creatures in the pool. Before stocking crab seedlings, it is necessary to clear the silt in the nursery pond and fill in the loopholes and cracks. Newly built crab ponds or crab ponds rebuilt with fish ponds should be cleaned and disinfected before stocking. The medicine for cleaning the pond is mainly bleaching powder. Usage of bleaching powder cleaning pool: First, calculate the pool water volume, and use 20g (20ppm) bleaching powder per cubic meter of water. Dissolve the bleaching powder needed in the nursery with water and immediately sprinkle it with water. Usually, crab seedlings can be released after 5 days of pool cleaning. Attention should be paid to the high alkalinity and high ph value of pond water in saline-alkali land, and it is not appropriate to use strong alkaline quicklime as pond cleaning medicine.

Third, pick up crab seedlings. To achieve the goal of "waiting for seedlings, waiting for seedlings in cars, waiting for seedlings in ponds", the crab seedlings should be put into the pond water for 2 minutes after being transported to the pond mouth, then hoisted for 2-3 times to adapt the crab seedlings to the water temperature and water quality of the pond, and then put into a cage for temporary cultivation. After the crab seedlings are put into the cage, the live crab seedlings will automatically swim out and then be removed from the cage. After the activity of crab seedlings is normal, the medicine Daphnia is fed.

Fourth, stocking density. Generally, 80- 150 (5- 10 kg) crab seedlings are stocked per mu. Large specifications and good quality, the density can be thinner, and vice versa.

5. Planting aquatic plants. When planting Alternanthera philoxeroides, duckweed and Sophora alopecuroides, it should be washed with river water to remove most of the attached shrimp and fish eggs, and then disinfected with 20ppm potassium permanganate solution to purify the water quality. Alternanthera philoxeroides, duckweed and Sophora alopecuroides can be used as habitats and bait for young crabs. Plastic greenhouse has played a great role in vegetable planting and rice seedling raising. However, the application and promotion of plastic greenhouse in river crab culture is little known. The author explored the method of raising river crabs temporarily by increasing temperature in winter, and its operation and application are as follows:

First, greenhouse construction.

Sufficient, fresh, clean water without pesticide and chemical wastewater pollution is the premise of temporary crab breeding. Generally, greenhouses should be built by rivers, lakes or large ponds, and well water can also be used (but oxygen-increasing equipment is needed).

The temporary pond is an east-west rectangle with a length of 4-10m, a width of10-100m and a depth of1-1.2m.. The dam and bottom are compacted to prevent water leakage and collapse. Large ponds should be equipped with inflatable pipes, and they should be inflated from the outside with air pumps when feeding. In order to facilitate fishing and management, the bottom of the pool can be covered with polyethylene net. Use soil, bricks, wooden stakes, bamboo poles, iron wires or film-pressing strips to fix agricultural films and build greenhouses. Greenhouse can be built in the shape of slope (slope facing south) or arch. According to the size and shape of the greenhouse, doors are left at both ends and sides for feeding and daily management.

After the pond is completed, drugs such as quicklime, bleaching powder, tea residue and croton are selected for disinfection. Invest in or plant an appropriate amount of aquatic plants that are easy to survive and not rot for crabs to inhabit. Add 0.5- 1 m deep water, and after the medicinal properties disappear, you can release the purchased river crabs.

Second, prepare the choice of crabs.

This is one of the keys to the success of temporary culture of river crabs in greenhouse. The selected river crabs should be of the same species, with similar specifications (generally only weighing 50- 100g), with strong physique and no diseases or physical disabilities. Most importantly, we must choose a big river crab in autumn, whose glands are not mature yet.

If the proportion of sexually mature crabs reaches more than 30%, it will lose its temporary reproductive value.

It is best to disinfect the selected river crabs once, and the available drugs are bleaching powder, formalin, potassium permanganate and so on. After disinfection, the river crabs are fed in the greenhouse. The stocking density should be 2-5 animals per square meter.

Third, feed with bait.

Using plastic greenhouse in winter can keep the water temperature above 15℃ for most of the winter, and ensure the normal growth of river crabs at suitable water temperature. When the water temperature drops below 18℃, the feeding intensity of the river crab is obviously reduced, but the greenhouse ensures the safe overwintering of the river crab. Eriocheir sinensis can be cultured in greenhouse for 3-5 months.

The main purpose of raising Eriocheir sinensis in greenhouse is to maintain its growth in the early stage, promote its gonad development in the later stage, accumulate nutrition and improve its quality for listing. Therefore, in these two stages, feed types and feeding methods are also different.

In the first stage (from June 165438+ 10 to one and a half months before going on the market), the bait should be mainly plant food. Such as soaked or cooked wheat, soybeans, sweet potatoes and vegetables. The daily feeding amount is about 5%-8% of the crab's weight, once in the morning and once in the afternoon, at10-1,at 4-5 pm, there are 3 baits and 7 baits.

In the later stage of feeding, the content of animal protein in food should be appropriately increased, and small miscellaneous fish and shrimp, silkworm chrysalis, snail meat and compound feed can be appropriately fed. However, in order to reduce the cost or when animal feed is not easy to obtain, the above method can still be used for feeding, and the effect is good.

Fourth, daily management.

The key to the success of temporary rearing of river crabs in plastic greenhouses in winter is to select the crab species to be bred, maintain a high water temperature and ensure good water quality.

In order to keep the water temperature, we must pay attention to the sealing between the plastic film and the pond, do not open the greenhouse door for a long time or frequently, and repair the damaged agricultural film in time. If you encounter heavy snow occasionally, you should clear the snow on the greenhouse in time. It is also necessary to flexibly adjust the water depth according to the weather conditions. When the sunshine is sufficient, the water depth can be reduced, which is beneficial to the rapid increase of water temperature; Water should be added in case of continuous low temperature or cloudy days until the pool is full.

Due to the small pond space, high stocking density, more bait and high water temperature, the leftover bait and excrement of river crabs are easy to rot, leading to the breeding of pathogenic organisms. Therefore, it is necessary to observe the feeding situation of crabs every day and adjust the feeding amount at any time. At the same time, according to the water quality, change the water in the pool to 1/5- 1/3 every 1-3 days when the air is warm in the afternoon. The water exchange should be carried out slowly, and the water inlet and outlet should be carried out at the same time at the opposite corner of the pond. Even if the water body is exchanged, the water temperature will not change dramatically.

In order to prevent diseases, appropriate amount of sulfonamides and antibiotics should be mixed into the feed every 1-2 weeks. You can soak the feed in a liquid medicine prepared with a prescribed dose of medicine and feed it with a small amount of residual liquid. If diseases occur, they should be dealt with in time and the dead crabs should be fished out of the pool. It is also necessary to prevent harmful organisms such as rats and snakes from entering the greenhouse. 1, Yangcheng Lake hairy crabs

This crab is produced in Yangcheng Lake, Suzhou, Jiangsu. It is a famous and famous product in China at home and abroad, and also the first famous aquatic product trademark in China, China. Yangcheng Lake hairy crabs have always had the reputation of being the best among crabs. Yangcheng Lake, with rippling blue waves, clear water like a mirror, hard water depth, lush aquatic plants, wide extension and pleasant climate, is the most ideal "Crystal Palace" for crabs to settle down and grow. The hairy crabs produced in Lianhua Island of Yangcheng Lake are authentic Chinese mitten crabs in the Yangtze River basin. Due to the excellent aquatic ecology, the crabs produced in Yangcheng Lake have the characteristics of crispy shells, full limbs and huge individuals.

2. Gucheng Lake hairy crabs

This crab is produced in Gucheng Lake in Gaochun District, Jiangsu Province. The waters of Gucheng Lake are hundreds of miles of Fiona Fang, with rippling blue waves, rich aquatic plants and extensive extension. The crabs grown here are particularly unique in shape and meat quality, with fresh and tender meat, delicious taste and rich nutrition. The crab meat in Gucheng Lake contains protein 14g, iron 13mg, riboflavin 0.7 1mg and vitamin A5960 international units. In the early years of the Republic of China, Shi Jinmo, one of the four famous doctors in Beijing, once compared the crab in Gucheng Lake to the first crab in the world and the first scholar in the world.

3. Liangzihu Hairy Crab

Hairy crabs in Liangzihu Lake, Ezhou, Hubei Province, are cultivated in an ecological way, and the products are marked with the origin. "Jiangxia poetry is in the ages, and the crabs on the shores of Liang Zi Lake are fat." The year before last, Yu improvised poems at the opening ceremony of the Cultural Festival, which made lake crab famous all over the world. Liangzi Lake is the second largest lake in Hubei Province, and two thirds of the water surface is in Jiangxia District. The lake is clear and the water quality reaches the second-class standard. The crabs produced are big, white, fresh and delicious. In 2004, "Liangzi" brand liangzi lake river crab was awarded the product of origin protection, and its trademark was awarded the title of "Hubei Famous Trademark" successively. Products are favored by consumers, selling well all over the country, and exported to South Korea, Japan, Singapore, Malaysia, Hong Kong, Macao and Taiwan, earning 5 million US dollars annually. Liangzi Lake is one of the largest freshwater lakes in Hubei Province, with the second largest lake area in the province. It is the hometown of Wuchang fish, which is famous at home and abroad. The crab culture area of Liangzi Lake is nearly six times that of Yangcheng Lake in Suzhou, and the output is twice that of Yangcheng Lake, and the water quality reaches the national second-class standard. Eating crabs in Liangzi Lake is a must.

4. Tianjin purple crab

This is a Chinese mitten crab, which is very small, only the size of a button. Uncover the crab cover, the crab yellow is purple in pig liver, and it turns orange after cooking, which is very delicious. Purple crabs are all produced in cold winter, so they are often used in assorted hot pot.

5. Laizhou crab

This crab is a famous specialty of Yexian County. Because Ye County was the seat of Laizhou Prefecture in ancient times, the name of Laizhou Big Crab has been passed down to this day. Laizhou crab has three protrusions on its back and nine serrations on its front side. The last tooth is particularly long and looks like a shuttle, so it is commonly known as "Portunus trituberculatus". This kind of crab is delicious and tender. The largest female crab weighs 0.75 Jin. The egg pieces of the female crab, the cream of the male crab, the white muscles in the claws and the meat of the hind legs of the big crab are even more delicious and unforgettable.

6. Portuguese fish

Swimming Crab in Xingcheng, Liaoning Province: This crab is white in color, tender in meat, greasy and delicious, and superior to sea crabs.

7. Nanhu crab

This crab is produced in Hangjiahu Net area of Zhejiang Province, and is famous for its big body and beautiful meat. In the past, lake crab here relied on natural breeding, and it was caught and listed in flood season every year. Artificial breeding and stocking have been started, and some achievements have been made.

8. Junshan Lake Hairy Crab

Junshan Lake Qingshui Hairy Crab is famous for its "green back and white belly, golden claws and yellow hair, huge size and delicious taste". It is a famous aquatic product brand in China, and the winner of Poyang Lake system. At the 2004 Yangtze River Eriocheir sinensis Exhibition, "Junshanhu" crab defeated "Yangcheng Lake" in Jiangsu Province, and won four laurels, such as King of Crab and Queen of Crab, in the competition of eight awards. Every year, thousands of tons of crabs come out of Junshan Lake and continuously flow to the dining tables of citizens in Nanchang, Hangzhou, Hong Kong and other domestic cities. They are not only sold well in China, but also exported to Japan, Southeast Asia and other countries and regions.

9. Crabs in Qiushui Lake, Minquan County

Quan Min river crab is pure natural, original ecology, pollution-free, high quality, big meat, yellow hair, golden claws, plump, delicious and nutritious. Named "Hometown of River Crabs in China" by China Fishery Association, it enjoys a high reputation in Beijing, Shanghai, Changsha, Jiangsu, Xi, Wuhan, Tianjin and Zhengzhou. Once exported to South Korea; In 2002, he won the gold medal in China (Shangqiu) Agricultural Products Expo, and in 2004, he won the first aquatic gold medal in China (Zhengzhou). Minquan County has been designated and awarded successively as "Key Fishery County in Henan Province", "Crab Breeding Base in Henan Province", "Advanced County in Fishery Work in Henan Province", "Healthy Breeding Demonstration Base of Ministry of Agriculture" and "Pollution-free Aquatic Products Breeding Base in Henan Province".