There are two kinds of crab seedlings: natural crab seedlings and artificial crab seedlings. The naturally captured crab seedlings have complex sources, many parallel imports, high value and many uncertain factors. One of the advantages of artificially cultivating crab seedlings is that the size of their parents can be strictly controlled, thus ensuring the purity and survival rate of cultivated crab seedlings, and the price is only about 1/2 of that of natural crab seedlings. Considering all kinds of factors, it is more economical to choose artificial crab seedlings.
(2) using special full-price granular materials
Compared with traditional feeding methods such as wheat and corn, the use of high-quality whole-grain materials has the following advantages: ① it is convenient to feed; (2) strong palatability, not easy to pollute water quality; ③ The breeding benefit is obvious.
(3) Reasonable feeding
The feeding amount at different growth stages is different, and the daily feeding amount should be increased or decreased according to the water temperature of the day and the food intake of the previous day. When feeding, the feed should be placed on the soil slope near the water level line or in shallow water near the pool, and the feeding time can be selected every evening.
(4) regulating water quality
(1) quicklime is often used to adjust water quality and keep water fresh.
② The water level in the crab pond is maintained at 0. 6- 1 m in spring, which can be deepened to 1- 1. 5 meters in summer.
(3) When changing water, the difference between the internal and external water levels should not be too high, and it is best to keep a slight running water all the year round.
(5) Pond patrol
Once a problem is found, measures must be taken immediately.
Living habits:
He often lives in caves in rivers and lakes, swings on mud dikes, hides during the day and comes out at night, and feeds on animal carcasses or grains. Every autumn, it grows plump and often swims back to the offshore to breed. The eggs carried by the mother hatch from March to May of the following year. After many metamorphosis, the larvae develop into young crabs, then return to the river and continue to grow in fresh water. Every autumn, when crabs breed and return, fishermen often set up a hairpin in rivers and lakes and trap them with lights at night.
Eriocheir sinensis lives in freshwater lakes and rivers, but breeds in brackish water at the estuary (salinity 18-26/ 1000, specific gravity1.016-1.020). From June to July every year, newborn crabs swim back to the river to enter fresh water, and then live on the banks of rivers and lakes. I like living in caves, or hiding in gravel and water plants. When digging a hole, 1 is mainly used to clamp the feet, and the feet only play an auxiliary role. Feeding on aquatic plants, benthos, organic debris and animal carcasses. Grab it with your paws when feeding, and then send the food to your mouth. When the nutritional conditions are good, the weight of young crabs can reach 50 to 70 grams, and the maximum weight can reach 150 grams. The gonads are mature and can participate in reproductive migration with the second-year-old crabs. If the stocking density is high or the growth is slow, the gonads of the second age are difficult to mature and cannot participate in reproductive migration.
companion
Eriocheir sinensis generally grows to the second instar in rivers and lakes, and develops rapidly from the end of September (around the autumnal equinox) when it molts into a blue crab. The reproductive index of female crabs suddenly rises from 0.36% before molting to 10 ~ 15% within 30 ~ 40 days. By the middle and late June of 10 (cold dew, first frost season), most gonads had developed to the fourth stage, so they left rivers and lakes for reproductive migration to the estuary and shallow sea. 165438+1After the beginning of October (beginning of winter), they gathered in the brackish water where the estuary and shallow sea meet, and began to mate and breed. The salinity in the breeding area of Eriocheir sinensis in the Yangtze River basin is 18-26/ 1000, the water temperature is 5- 10℃, and the time is 12 to March of the following year. During mating, the male crab grips the female crab's foot with pliers, aligns one end of the adapter with the female hole, and inputs semen into the female crab's seminal vesicle. The whole mating process lasted for several minutes to 1 hour. Female crabs usually lay eggs within 7 ~ 16 hours after mating. The fertilized egg is attached to the bristles of the abdominal limbs of the female crab. When the water temperature is 10 ~ 17℃, the fertilized eggs hatch into larvae after 30 ~ 60 days.
type
Float in the shallow sea of estuary for more than 35 days, molt for 5 times, and then enter the stage of megalopa. At this time, it is also engaged in planktonic and benthic life, which can be traced back to lakes and swamps in the upper reaches. After 6 ~ 10 days, the big-eyed larvae shed their shells and became young crabs, and began to crawl at the bottom.
After all the eggs are hatched, the female crab lies dormant on the sand dunes in the estuary shoal, with bryozoa and tapeworms attached to her head, breastplate and limbs, and the crab slave often parasitizes her abdomen. Postpartum females died one after another from the end of June to the beginning of July. From the larval point of view, the life span of the female crab is 2 feet, while the male crab dies after mating, and its life span is 2 months shorter than that of the female crab. The life span of mature Eriocheir sinensis is only 1 year, and females are dominant. Individuals with slow gonad maturation live longer, some of which can reach 3 to 4 years.