Crayfish Culture Technology
Cherax quadricarinatus is commonly known as “Australian freshwater lobster†and belongs to the crustacean, decapoda, crustacean, and light-shelled shrimp. Its origin is in a near-bay river with a tropical and subtropical climate on the northeastern coast of Australia. China's introduction of trials in the early 1990s confirmed that the red-claw crayfish have large individuals, fast growth, miscellaneous feeding habits, high aquaculture production, delicate meat quality, and high meat yield (the edible part accounts for about 40% of the body weight). An excellent crayfish species worthy of promotion and breeding. Here are some biological characteristics and artificial breeding techniques of freshwater lobster.
1 Breeding habits Crayfish is native to tropical regions of Australia and has a rapid growth rate of 50-80 g within 6 months.
Red-cheeked crayfish typically reach sexual maturity at 6-12 months of age. The male larvae of sexually mature males have an obvious red or orange-yellow marking on their extensions, and a pair of papillary stimulants on the base of the fifth pair of feet. The larvae of males exceed the body length. The females have a pair of genital holes in the base of the third pair of stepped feet. The chela of the male is blue and the length is less than the body length. Sexually mature red-handed crayfish naturally reproduce in ponds when the water temperature is above 21°C.
Cheetosma crawfish reproduces for a long time, beginning in April and ending in October. The optimum breeding temperature is 22-33°C, and the optimum water temperature is 28-30°C. Mature females must undergo shelling prior to mating to mate. After mating, females ovulate within 24 hours and then combine with sperm to fertilize. The fertilized egg is orange. After spawning and fertilization, their eggs are hatched by the mother. Usually, the incubation period is 30-31 days when the water temperature is 28-29°C. Red-claw can lay eggs 2-3 times a year.
2 Growth Environment Factors
2.1
The water temperature of red-caught crayfish adapts to the tropical habits, is able to endure high temperature, suitable temperature range for growth is 24-42°C, and falls below 21°C for feeding and the growth rate is reduced. Below 10°C, shrimp grows. Under 9°C, shrimps that grow too long will also die. Therefore, wintering in areas with low winter temperatures requires overwintering management.
2.2
In addition to high temperature resistance, redox crayfish is also resistant to hypoxia. Under normal conditions, the dissolved oxygen in the pool is maintained at 4-5 mg/L, and the growth is normal. Adult shrimp can tolerate 1 mg/L of dissolved oxygen and can climb out of the water for a short period of time to breathe air. Juveniles are relatively sensitive to low dissolved oxygen and shrimps do not survive in 1.2 mg/L water.
2.3
The pH is suitable at a pH of 6.5-9. The incubation period should be above 7 because acidic water is not conducive to shelling and growth, it will increase the death of shelling or extend the shelling time.
2.4
Salinity crayfish do not require high salinity, so they can grow smoothly in freshwater ponds. At the same time, the larvae can still adapt to the salinity of 3g/L and the adult shrimp in the water of 5g/L. Therefore, larvae can be used for 1% and shrimps can be soaked with 3% saline for a short time to kill the surface parasites.
3 Breeding technology
3.1
Shrimp cultivation 3.1.1 The conditions of the cultivation pond are for the convenience of management. The cultivation pond is generally a cement pool of 50-300 square meters, and the depth of water storage is 1m, which requires convenient drainage and drainage. At the same time, concealed objects are placed on the bottom and surface of the pool, accounting for 1/4-1/3 of the bottom and surface of the pool, in order to increase the effective living area of ​​the shrimp.
3.1.2
Stocking Density In the first four weeks of larval rearing, the stocking densities in the nursery ponds should not exceed 1000/m2. Proper spawning and timely stocking help to increase the survival rate, and the general breeding survival rate can reach 50%-70%.
3.1.3
Three days after the start of the feeding of the bait, the steamed egg + fish pulp can be used to feed the prawn on all four sides, gradually replacing the shrimp with the crude protein content of 44%-46% with open bait and Artemia. The shrimp feeding rate was 3-5 times per day. When the juvenile shrimp grows to more than 2cm, it can be fed pellet feed. The feed amount is 15% of the pond shrimp weight, and it should be increased or decreased according to the water temperature, food intake and growth conditions.
3.1.4
Water quality control requires fresh water and a little more transparency. It's better to be a bit tricky. Avoid excessive feeding. There should be no leftovers and waste deposits in the water. Clean up in time.
When the larvae grow to 3cm and the body weight is about 1g, they can be put into ponds and cultured into shrimps. To ensure the survival rate, it is also possible to keep the larvae in the pond and continue to dilute them, so that the shrimp can reach 2g or more, and then put into shrimp ponds.
3.2 Pond farming
3.2.1
The pond condition is used for the area of ​​1-1.5 mu of ponds for red-claw crawfish breeding, the depth of pool water is 1-1.5m, and the bottom of the pond is slightly sloped, with good drainage system and oxygen system, no leakage, and a good defense Escape facilities. Must be clear pond before stocking, in order to avoid predators and pathogens remain in the pond, the method is the same as the general aquarium, lime per acre with 150-300kg dry clear pond. Red-claw crayfish is afraid of light and is good at climbing and climbing. It requires aquatic plants on the water (about 1/3 of the water surface), water plants on the bottom of the pond (black algae, etc.), and a bamboo tube or other similar object at the bottom of the pool. For its burrowing.
3.2.2
The toxicity of lime water disappears after 7-10 days when shrimps are released, and the seedlings can be released after the water quality is normal. The general stocking density is 7,000-10,000 tails/mu, stocking for about one month, and 50-250g/tailed whitefish 60-100 tails/mu can be mixed in a timely manner. Freshwater lobsters are benthic crustaceans. Proper mixing of upper and middle filter feeder fish can improve the growth environment of lobsters. On the other hand, these fishes are more sensitive to dissolved oxygen in water and can be used as indicator fish for hypoxia in ponds. Do not breed carnivorous fish and other food-eating fish so as not to affect the growth of crayfish.
3.2.3
Under normal conditions of water quality management, water quality management is mainly to ensure that the dissolved oxygen in the shrimp pond water is sufficient and the water quality is fresh and good. It is better to add 1/5-1/4 of the fresh water to the pool water every day. Regular lime water is used to improve water quality, increase calcium, and facilitate shrimp shelling and improve survival.
3.2.4
Feeding management mainly feeds fish and shrimp with food, and the daily feeding amount is 3%-10% of shrimp body weight. Feeding points two times sooner or later, due to their eating habits generally in the evening and night by the pool side feeding, so the evening feeding should account for about 2/3 of the total. Feeding takes a combination of fixed and poolside splashes. Since red-caught crayfish are omnivorous and rotten food, it is necessary to appropriately increase the feed for plant feed. In the early stage of cultivation, some hay can be put in the pool and 40 kg per month can be cast; in the later period, soybeans and barley can be fed.
The whole feeding period was adjusted appropriately according to the water temperature. Since the water temperature was low, the feeding was weak, and the feeding rate was low, about 6% of the body weight was fed, the middle water temperature was high, and the ingestion was vigorous, feeding about 10% of the body weight. Afterwards, as the water temperature decreases, the feed rate drops, reaching about 3%.
3.2.5
Control of shrimp disease Shrimp crayfish is susceptible to a "crayfish shrimp" disease, which is caused by a fungal infection. The suitable growth temperature of the fungus is not higher than 18°C. When the water temperature is higher than 21°C, the growth of the fungus is inhibited. Therefore, as long as the temperature of the shrimp when the shrimp is stocked and caught is controlled to be above 21°C, the crawfish will not get sick.
3.2.6
There are two methods for catching crawfish: shrimp cage trapping and dry pond fishing. When the water temperature falls below 18°C, shrimp ponds that are not ready to overwinter can be collected in dry ponds. As long as the pond water is drained, the shrimp can be collected in the pond and the pond should be set in the outlet. Collect shrimps that flow down the water. Usually a small amount of fishing, can be used trapping shrimp cage, shrimp cage with a mesh weaving, mesh size is about 2cm, the shape of two kinds of upright and pyramidal. When trapping, put the bait into the cage, then sink into the pond and immediately collect the shrimp from the cage.
After 5-6 months of cultivation, shrimp production can reach 70-110kg/mu, individual specifications 70-180g, up to about 450g.
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