English name: RedSwamp Crayfish or Red Swamp Crayfish

Chinese name: Also known as crayfish, the scientific name is Procambarus clarkii.

Classification: Crustacea, Decapoda, Reptilia.

brief introduction

There are more than 400 species of lobsters in the world, and North America is the continent with the largest distribution of lobsters. There are two families (Crabmeat, Crayfish), 12 genera and more than 300 species distributed in North America. Among more than 300 species of lobsters, most of them have low economic value, among which the species of Cambarellus is the smallest, and the individual weight rarely exceeds LG. Lobsters with large individuals (up to 50-80g per fish) and important economic value include Procambams, Cambarus, Pacifastacus and Orconectes, among which Procambarus clarkii accounts for 70-80% of the total lobster output.

China is one of the countries with the least distribution of lobsters, with only four species, namely Procambarus clarkii, Cambaroides dauricus, C. Schrenkii and C. Similis. The last three species are only distributed in three northeastern provinces of China, North Korea and Japan.

morphological character

(1) shape

It is the largest shrimp in the world with a large cylindrical shape. The crustacean is firm and thick, and the head and breastplate are slightly flat on one side. The front edge does not heal with the anterior plate of the mouth, and the side edge does not heal with the abdominal breastplate of the chest and the base of the chest limb, except for the crayfish family. The neck groove is obvious. The first 1 antenna is short and small, Shuang Bian. The second antenna has developed scales. All three pairs of jaws and feet have external limbs. All the steps are single-branched, and the first three pairs are chelated, among which the first pair 1 is particularly strong and thick, so it is also called crayfish. The last two pairs of feet are simple and claw-shaped. Gills are filamentous gills.

(2) appendage

Lobster head has 3 pairs of tentacles, which are thick near the head and small and sharp at the tip. A pair of tentacles on the outer edge of the head are particularly thick and long, generally longer than the body1/3; Between a pair of long tentacles are two pairs of short tentacles, which are about half the length of the body. When perching and crawling normally, all six tentacles extend forward. If frightened or attacked, two long tentacles bend to the tail to prevent the tail from being attacked.

There are 5 pairs of feet in the chest, the ends of the 1-3 pairs of feet are pincers, and the ends of the 4-5 pairs of feet are claws. The second pair of walking feet are particularly developed and become very large claws. The male claws are more developed than the female ones, and the front outer edge of the male lobster has a bright red film, which is very conspicuous. Females don't have this red film, so this is an important feature that distinguishes males from females.

There are five powerful tail fans at the tail. During the brooding period and incubation period, the tail fans of the mother shrimp bend inward, crawl or be attacked, so as to protect fertilized eggs or young shrimps from damage.

Habitat habit

① Benthic

Lobsters like to inhabit hidden objects such as aquatic plants, branches and crevices. The shrimp lies in the daytime and comes out at night, and it doesn't like bright light. Under normal conditions, they are mostly hidden in the deep water or hidden objects during the day, and rarely move. In the evening, they start to move after the sun goes down, and most of them gather in shallow water to crawl for food or find a mate. If frightened, flee back to the deep water quickly. This shrimp prefers to crawl, but does not like swimming. It crawls forward during foraging and activities, and quickly jumps backward when it is frightened or meets the enemy.

② Hydrotropism

Lobsters have a strong tendency to flow, like new water and living water, go upstream against the current, and like to live in groups. In aquaculture ponds, groups often gather around the water inlet. In rainy days, the shrimp can stay or escape on the shore for a short time against the current, and it will climb up to the shore to live when the water environment is not suitable, so the breeding ground should have fence facilities to prevent escape.

③ Aggressive

Lobsters are aggressive by nature, and when they are short of feed or struggle to live in caves, they often bully the weak, bully the small and fear the big.

Larvae has strong regeneration ability. The lost part is regenerated at the second molting, and it will recover after molting several times, but the new part is shorter than the original one. This self-cutting and regeneration behavior is a protective adaptation.

④ Dig a hole

Lobsters like to dig holes and are good at digging holes.

First, the depth and speed of digging holes.

The depth of lobster digging hole is the key factor to determine its harm degree. According to our field survey of 35 lobster caves, the depth of most caves is 50-80 cm, accounting for about 70% of the surveyed caves, and the depth of some caves exceeds 1 m, and the longest cave we measured is 2.1m. Usually, it is possible for lobster caves with horizontal plane direction to exceed the depth of 1 m, while caves with vertical depth downward are generally shallow. Lobsters dig holes quickly, especially in a new living environment. After putting lobsters in Dafeng lobster experimental pond A for one night, it was observed that under sandy soil conditions, the depth of new holes dug by most lobsters was more than 30 cm.

Second, the location of the lobster cave.

The location of the hole where lobsters dig holes is usually at the horizontal level, but this choice often makes the hole higher or lower than the horizontal level because of the change of water level, so generally, the lobster hole is the most at the height of 20 cm above and below the water level. However, the location of lobster digging holes is not very strict. In our experimental base, there are lobster caves on the water bank, the slope in the water and the bottom of the pool in shallow water, which are concentrated in the lush water plants.

Thirdly, the influence of living environment on lobster burrowing.

The sediment condition of water body has obvious influence on lobster burrowing. In sandy soil with lack of sediment organic matter, lobster burrows more, while hard soil burrows less. Under the conditions of rich water quality, more silt at the bottom and rich organic matter, the number of lobster caves is obviously reduced. However, no matter what kind of living environment, the number of lobsters digging holes increases obviously during the breeding season.

adaptability

The environment requires that lobsters have strong adaptability to the environment, and all kinds of water bodies can survive, no matter lakes, rivers, ponds, river ditches and paddy fields, even in some water bodies where it is difficult for fish to survive. Lobster has a strong tolerance to hypoxia, and it can climb ashore for gill breathing to survive in an anoxic environment. The PH value of water quality is in the range of 5.8-9, and it can still survive normally when the dissolved oxygen is lower than1.5 mg/L. Normal growth requires dissolved oxygen above 3 ml/L.

② water temperature

The suitable water temperature for lobster growth is 24℃-30℃. When the temperature is lower than 20℃ or higher than 32℃, the growth rate decreases, and the survival rate of larvae is extremely low when the water temperature is below 15℃. The temperature difference between day and night in the feeding waters should not be too large, and the temperature difference between day and night of young shrimp should not exceed 3℃, and that of adult shrimp should not exceed 5℃, otherwise it will cause great losses.

In the Pearl River Delta and the coastal areas of South China, it is generally possible to overwinter naturally. In order to prevent a large cold wave attack, the overwintering adult shrimp can be placed in a deep culture pond, and a wind wall or a cold shed can be built at the northwest corner of the culture pond. The suitable water temperature for embryo development is 22℃-32℃. If it is kept at 28℃-30℃, the incubation time can be greatly shortened.

③PH value

The suitable PH value of lobster is 5.8-9, but it is required that the PH value is about 7.0 and the dissolved oxygen is above 3 mg/L during the breeding and incubation period. However, it has strong resilience, can live in some domestic sewage and mild industrial wastewater, and is also distributed in ditches and channels in pesticide application areas.

Feeding habits and growth

1, feeding habits

Lobster is an omnivorous animal, but its feeding habits are slightly different at different development stages. The newly hatched larvae feed on their own yolk, and soon after, they feed on small zooplankton such as rotifers. As the individual grows, they feed on larger zooplankton, benthos and plant debris. Adult shrimps eat both animals and plants, plant debris and animal carcasses as their staple food, as well as water worms, chironomid larvae, small crustaceans and some aquatic insects. In the case of artificial breeding, the larvae can be fed with the nauplii of the adult worms, spirulina powder, etc., and the adult shrimps can be fed with artificial compound feed, or the artificial compound feed is mainly supplemented with animal and plant debris.

2, molting and growth

Lobster grows by molting, and the new shell after molting hardens after 12-24 hours. Under the condition of water temperature of 25℃-30℃, the body weight can reach 60-150g after feeding for 6-8 months. The general trend of lobster growth is: from hatching to weighing 20 grams, the growth rate is accelerated; At the stage of reaching 50-100g, its growth rate remained at a relatively stable level, and after this stage, the growth rate showed a downward trend. Thus forming an inverted U-shaped growth curve. Molting can be divided into two types: long molting and reproductive molting. After the young shrimp leaves the mother, it quickly enters the molting 1 time, puts on a soft and wrinkled new skin, and quickly absorbs water and grows. This is growth molting, from larva to adult * * * molting1time. Female shrimps begin to reproduce and molt after sexual maturity, and then they must reproduce and molt before each mating and spawning.

Reproductive habit

1, male and female identification

There are differences between male and female lobsters, which can be identified mainly by the following methods:

1) Parents of the same age, the females are bigger than the males;

2) For the parent shrimps with similar body length, the male big pincers are thicker than the female ones, and the spinous processes on the wrist joint and palmar joint of the male big pincers are long and obvious;

3) The 1st 1 abdominal limb of female shrimp degenerates and is very small, and the 2nd abdominal limb is normal; the 2nd 1 abdominal limb of male shrimp becomes tubular, longer and reddish, and the 3rd, 4th and 5th abdominal limbs are white, which is the most obvious distinguishing feature between males and females in appearance.

2. Sexual maturity

Lobsters reach sexual maturity at the age of 6- 12 months in natural environment, and the weight of individuals who have reached sexual maturity is generally 30-100g. Under the condition of artificial feeding, the accessibility is generally mature in 6 months. Parent shrimps of the same age, generally male shrimps are slightly larger than female shrimps. The sex ratio of lobsters raised in the same pond is close to1:1.

3. Reproduction

Lobsters mature at the age of 9- 12 months, and the mating season is generally from late April to July, and the peak of group mating is in May. When mating, the female shrimp lies on her back on the water surface, and the male shrimp holds the female shrimp's front feet with dragon feet on it, and the female shrimp is held by her feet to insert the connector into the female body. The mating time is 10-30 minutes. 3- 10 hours after mating, the female shrimp began to lay eggs, which were one-time eggs, and the eggs produced adhered to the bristles of the gastropod. The number of eggs held is about 500- 1500, which varies with individual size. The length of embryo development is closely related to the water temperature. The higher the water temperature, the shorter the incubation time, while the lower the water temperature, the longer the incubation time. The hatched young shrimps are still attached to the swimming feet of the parent shrimps and grow for a period of time under the protection of the mother. Lobster larvae at different stages are attached to the maternal abdominal swimming feet, and the largest lobster larva is 1.0- 1. 1 cm. From the early autumn of the first year, the growth, development and wintering process of lobster larvae are attached to the mother's abdomen, and they don't leave the mother's life until the next spring. Lobster, a way of breeding offspring, ensures a high survival rate of offspring.

4. Laying eggs

Lobster is a type of spawning multiple times a year. When the water temperature rises above 20℃, the parent shrimps begin to lay eggs. The spawning season can last for 6 months in eastern Guangdong, and they can lay eggs 3-4 times a year. The amount of eggs laid varies with individual size and gonad development, generally 300- 1000 eggs each time. Larger females have more eggs.

5. Embryo development

The fertilized eggs of lobsters adhere to the abdominal limbs of females for embryonic development, and hatch into larvae after 5-8 weeks. The development speed of fertilized eggs is related to the water temperature, and the incubation time is short at high temperature. The initial egg diameter of the fertilized egg is 2mm. With the development of the embryo, the color of the fertilized egg changes regularly in different development stages, from light milky white at the time of initial delivery to dark brown, with black eye spots, and finally to orange. At this time, the larvae are about to hatch. At the water temperature of 32℃, the above-mentioned colors appeared in sequence during the development of fertilized eggs: light milky white 1-5 days; Dark brown 12- 14 days; Eye point appears for 20-33 days; Orange for 28-35 days; Break the membrane and leave the mother for 35-40 days.

6. Larval development

The newly hatched lobster larvae are basically the same as adults, with an average body length of about 9.5 mm, and continue to cling to the abdominal limbs of the female shrimp for 1-2 weeks, during which the larvae will occasionally leave the mother for activities. The newly hatched larvae depend on the yolk sac for nutrition until they live completely independently after hatching for 3 weeks. Under suitable conditions, after 50-60 days, the larvae molt for 5-8 times and the weight reaches 0.5-2g, then they can be released into the pond for adult shrimp culture.

Lobsters in China

The scientific name of freshwater lobster is Procambarus clarkii, which belongs to Arthropoda, Crustaceae, Shrimp Family and Procambarus, and it is one of the most valuable species in the genus Procambarus. The shrimp has strong adaptability, can widely live in freshwater lakes, rivers, ponds, ditches and rice fields, and is mainly distributed in Jiangsu, Zhejiang, Hubei, Hunan, Anhui, Shanghai, Shandong and other provinces (cities) and regions 10, and is basically a natural wild resource. According to statistics, by the end of 2003, the country had exported about 225,080 tons of freshwater lobster products, earning US$11056 million, using freshwater lobster raw materials1/89,200 tons, and the farmers benefited from catching freshwater lobsters accumulated about 6.67 billion yuan. The rise of export processing industry has brought out a number of biochemical enterprises that refine chitin products, thus producing more than 40,000 tons of chitin end products, with an economic value of14 billion yuan.

The selling price of export products is low, and the comparative benefit continues to be low. The highest selling price of exported freshwater lobster products is 1995, and the selling price of shrimp products is 60,000 yuan/t ~ 75,000 yuan/t, which is less than the ex-factory price of American shrimp products1/2; The profit of shrimp products is as high as 30,000 yuan/t ~ 45,000 yuan/t, and the profit of whole-limb lobster products can reach 1 10,000 yuan/t ~10.8 million yuan/t. With the increase of raw material price of freshwater lobster, the decrease of export selling price and the increase of processing cost, the comparative benefit of export processing enterprises has greatly decreased.

The export trade market is unpredictable and risky, and its ability to break through foreign technical and trade barriers is relatively weak. More than 95% of China's freshwater lobster products are exported to the European Union and the United States, accounting for about1/2 of the total. For more than ten years, the export of freshwater lobster products has not been smooth sailing, and it has been undergoing tests, which has also screened and eliminated a large number of production enterprises. Mainly reflected in: ① After the EU and the United States successively implemented the health registration system and HAC-CP registration system, a number of production enterprises were eliminated. ② The United States has continuously introduced anti-dumping bills against freshwater lobster. Most domestic production and operation enterprises in China withdrew from the American market because of the high tariff of 30% ~120%. The United States continues to implement anti-dumping duties this year, and the tax rate is as high as 223.01%.China's freshwater lobster export market has lost half of its territory, and the export industry has been severely hit, resulting in heavy economic losses. ③ European and American countries implement a dynamic quality inspection system for imported freshwater lobster products. Due to the safety and hygiene problems of many crayfish enterprises in China, some of them have been suspended for rectification and their foreign registration codes have been revoked, and some products have even triggered a comprehensive embargo on animal-derived foods including freshwater lobster products.

The safety and hygiene problems of products occur from time to time, and the hidden dangers of safety and hygiene are still outstanding. In the past ten years, the quality problems of exported freshwater lobster products can be said to have occurred every year, which has triggered a series of foreign trade quality disputes and trade frictions between governments, such as the "blacklist" of the US FDA, the comprehensive embargo of the European Union, and the expansion of sampling inspection at the time of customs clearance. Tracing back to the export history, the content of quality problems is constantly evolving. Before 1999, the focus was on poor quality and poor packaging, and the problems of bacterial hygiene indicators such as Staphylococcus aureus, Vibrio parahaemolyticus, Vibrio cholerae, Listeria, Salmonella, Vibrio vulnificus and Vibrio alginolyticus. In 2000 and 2002, the focus of quality problems was on chloramphenicol; Since 2002, the focus has been on nitrofurans and their metabolites. Although these problems are important factors of technical barriers to trade in importing countries, some products do have safety, hygiene and quality problems.

The industry order is chaotic and the quality level is uneven. The main problems in the industry are as follows: in order to compete for foreign customers, production and operation enterprises dump at low prices and crush the market; Enterprises in different provinces and regions have differences in safety and health self-control ability, and the safety and health monitoring work at the source of some enterprises is still very weak, and the connection between the automatic control system and the official monitoring system is uncoordinated; The activities of unregistered underground factories are rampant. These factories have poor sanitary conditions, low management level, and many problems in product safety and hygiene, and the products basically flow to the international market, causing serious hidden dangers and problems in safety and hygiene quality; In order to make huge profits, some registered enterprises exporting freshwater lobsters violated the health registration numbering system of AQSIQ and bought the parallel exports of the second underground factory or enterprise.

With the rapid development of natural resources, freshwater lobster resources are becoming scarce. Although freshwater lobsters are relatively fertile, there were once many natural resources in the Yangtze River basin. However, predatory fishing and acquisition and raw material wars are stronger. Over the years, large and small export-plus-T enterprises and underground factories have ignored the natural reproduction law of freshwater crayfish, purchased them without any specifications and spared young shrimps under 50 mm Shrimp farmers have caught them without limit, and even used pesticides to trap them in a few places. As a result, freshwater crayfish resources are becoming increasingly depleted. In August, 2004, many added enterprises ran out of shrimp or bought raw materials for a few days to process them in one day.

The domestic consumer market has sprung up suddenly, and the export industry will face cooking without rice. In recent years, driven by the export market, freshwater crayfish has gradually evolved into a delicious dish on the table in China. Now, the shrimp-eating atmosphere in Nanjing, Beijing, Shanghai and other large and medium-sized cities is booming, and many restaurants have reached the point where there is no shrimp. It is understood that in the summer of 2004, the daily consumption of freshwater crayfish in Nanjing alone reached 70 t ~ 80 t, which is the sum of the daily raw material demand of two or three domestic export processing enterprises, and the purchase price of raw shrimp is much higher than that of Canada lT enterprises. For example, even the purchase price of crayfish of about 60mm in Shanghai, Nanjing and other cities is as high as 10 yuan/kg ~12 yuan/kg.

Nutritional and medicinal value

It is the key to choose shrimp when making Xuyi 13 sweet lobster. You must choose a fresh and big one, which looks bright on the surface and is stiff, and if you buy female shrimp, the taste will be more delicious. The way to identify a female lobster is to see if there are a pair of triangular spines on the lower epidermis of the head-body connection part of the shrimp, and if there are, it is a female crayfish. Also, after buying shrimp, it is best to put it in water for a day to make it spit out the sediment in its body.

Lobster Crayfish has the same nutritional content as sea shrimp, and sea shrimp tastes fresher, so people think it has high nutritional content. The types and contents of nutrients in aquatic products are no less than those in livestock and poultry meat, while the nutritional components in various shrimps are almost the same. All kinds of shrimps are high in protein and low in fat, with the protein content accounting for about16%-20% and the fat content less than 0.2%. Moreover, the fat contained is mainly composed of unsaturated fatty acids, which is suitable for human body to absorb. The content of trace elements such as zinc, iodine and selenium in shrimp meat is higher than that in other foods. At the same time, its muscle fiber is tender and easy to digest and absorb.

Lobster is not only white and tender, delicious, high in protein, low in fat and rich in nutrition. Lobster also has medicinal value, which can eliminate phlegm and relieve cough, and promote the wound healing after operation.

economic value

China's crayfish are mainly distributed in the middle and lower reaches of the Yangtze River, such as Jiangsu, Hubei, Jiangxi and Anhui, and grow in rivers, lakes and other water bodies, with an amount of more than 60,000 tons. Jiangsu is a key province for processing and exporting freshwater lobsters. There are more than 60 processing enterprises in the province, and the annual export volume of processed lobsters is about 6,000 tons, accounting for more than 90% of the national lobster export volume. Crayfish has become the main variety of Jiangsu's freshwater aquatic products to earn foreign exchange. At present, Jiangsu's freshwater lobster processed products are mainly exported to the European Union and the United States, and more than 60% of them are exported to the European Union. Because the freshwater lobster processed products are sold to the international market, consumers can eat them directly, so the importing countries have strict requirements on their hygiene, quality and quality, and also have higher requirements on lobster growth, fishing and processing conditions and technical level. In order to meet the requirements of importing countries for product quality, Jiangsu lobster processing enterprises have invested hundreds of millions of yuan in recent years, among which 14 factories that applied for registration in the European Union have invested hundreds of millions of yuan successively to strengthen equipment transformation and improve internal management level.

Lobsters are sexually mature when they weigh about 25-30g, and they mate and lay eggs when the water temperature is above 20C. The diameter of eggs is large, reaching1-2mm. The eggs produced are attached to the abdomen until the larvae are hatched. The number of eggs held is 300-1200, and the incubation time is about 6 weeks.

Freshwater lobster culture technology

Freshwater lobster, commonly known as Australian red crayfish. The introduction of culture experiments in China in the 1990s was successful. The shrimp has the characteristics of fast growth, large size, high yield, miscellaneous eating habits and high meat yield. The aquaculture technology is introduced as follows:

First, the pond conditions. The water surface of the pond should not be too large, and it is suitable for the water surface 1~2 mu and the water depth 1~ 15 m, with a perfect drainage system and aeration system; There is a slight slope at the bottom of the pond without leakage, and the escape prevention facilities are repaired. Before stocking, the pond must be cleaned (dry) to remove impurities and weeds, so as to avoid leaving enemies and pathogens in the pond, and each mu of water surface should be disinfected with quicklime 150~200 kg. Lobsters are fond of shade and afraid of light, and are good at climbing and escaping. It is required that there are aquatic plants on the water, accounting for about13 of the water surface, and aquatic plants can be planted, such as verticillata and POTAMOGETON crispus. At the same time, hidden objects such as bricks, stones and bamboo tubes should be set at the bottom of the pond for them to inhabit and burrow.

Second, shrimp fry stocking. After 7~ 10 days, the seedlings can be released after being disinfected with lime water, which requires high water temperature. The suitable growth water temperature is 20℃~30℃, and it is rarely eaten when it is lower than 15℃. The water body should maintain high dissolved oxygen, and the dissolved oxygen should be above 50 mg. The transparency of water body should be 30~40 cm. The PH value is 7.0~8.5. The shrimp fry with a density of1.5 ~ 3.5cm are stocked, and the stocking density is 4000~7000 fish/mu. When releasing the seedlings, put the plastic bag containing the shrimp seedlings in the pond for 30 minutes before opening it, so that the shrimp seedlings can gradually adapt to the water temperature in the pond, which is beneficial to improving the survival rate of the shrimp seedlings. Stocking 1 month or so, 60~ 100 silver carp with 50 ~ 250g/tail can be stocked in time. Freshwater lobster is a benthic crustacean. Proper mixed culture of pelagic filter-feeding fish can not only improve the growth environment of lobster, but also be used as an indicator fish of hypoxia in the pond. But don't mix carnivorous and herbivorous fish to avoid affecting the growth of lobsters.

Third, feeding. After the shrimps were put into the pond for 30 minutes, they began to be fed with feed. In the early stage, cooked soybeans were mainly fed for beating, and a small amount of small miscellaneous fish and snail meat were supplemented. The feeding amount was 6-8% of the shrimp's weight, and they were fed twice in the morning and evening. According to the feeding habits, the evening accounts for about 2/3 of the total daily amount, and the combination of fixed points and splashing by the pond is adopted. In the middle stage, the water temperature is high and the food intake is vigorous, and the feeding amount is 10%. In the later stage, shrimp bait can also be fed, and some compound feeds such as miscellaneous fish, soybean meal, wheat bran and vegetables can be fed 25% each. The daily feeding amount changes with the water temperature, so it can be flexibly controlled.

Fourth, daily management. ① Strengthen water quality management to ensure adequate dissolved oxygen and fresh water quality. (2) prevent shrimp from floating in high temperature season, and increase the aerator. (3) when the water quality is too fat, use quicklime to kill plankton and spill it all over the pool. (4) pay attention to patrol the pond, remove enemy creatures, frogs, snakes, etc.