Culture Technology of Penaeus chinensis

We usually refer to the shrimp of the genus Penaeus and Penaeus, which belong to Arthropoda, Crustacea and Decapoda. Penaeus chinensis is mainly distributed in the Yellow Sea and Bohai Sea of China. It can sometimes be found in the East China Sea and South China Sea, but the quantity is very small. The main species of Penaeus chinensis (also known as Penaeus oriental shrimp) in China is introduced as follows.

Reproductive habits and life history of Penaeus chinensis

The mature stages of female and male prawns are different. The male shrimp can reach sexual maturity in that year, while the female shrimp will not mature until April or May of the following year. After the male shrimp matured, it mated with the female shrimp from mid-October to early November. During mating, the sperm is sent into the seminal vesicle of the female shrimp by the male shrimp before the new carapace is hardened. After mating, the seminal vesicle of female shrimp changed from flat and transparent to plump and milky white.

From April to June in the second year after mating, the gonads of the female shrimp matured and laid eggs. The water temperature of spawning in the natural sea area of Penaeus chinensis was 13 Mel 18 ℃. Under the condition of temperature control, artificial feeding can advance to March to lay eggs. Prawns have the habit of spawning many times (in batches). When the female shrimp lays eggs, she releases the sperm from the seminal vesicle to combine with the eggs.

From spawning, fertilization and hatching to larval shrimp, Penaeus chinensis has to go through three completely different shape stages, nine times of shelling, that is, nauplius, flea larva and Mysis larva to larval shrimp. After 14-22 times of shelling, the young shrimp reached sexual maturity to mate and reproduce.

Environmental factors of Penaeus vannamei breeding

Shrimp breeding is generally carried out in cement ponds in the south, and the suitable environmental factors for shrimp breeding are as follows:

1. Water temperature: the optimum water temperature for spawning and hatching of fertilized eggs is 18 ℃, 20 ℃ for nauplii, 22 ℃ for flea larvae and 23 ℃ for Mysis larvae, but when the larvae are ready to leave the pond for 3 days, the water temperature should gradually drop to close to that of the culture pond. In order to avoid death due to the excessive temperature difference between the pond and the culture pond.

2. The pH value is generally between 7.8 and 8.6.

3. The salinity is generally about 25 ‰.

4. Dissolved oxygen is above 4mm liter.

Culture technology of prawn

1. Pond cleaning: after the completion of the pond or the restoration of the old pond, the pond and pond cleaning should be carried out 20 days before release, including the removal of silt, algae and animal enemies. The way to remove enemy pests is: the pond without stagnant water can be removed by draining the pond water after the shrimp harvest and exposing it to the sun for a winter. However, the exposed pond can not be drained and needs to be removed with medicine. Commonly used drugs are tea seed cake, bleach, fish rattan essence, quicklime and so on.

2. Food biological culture: after removal, biological bait can be cultured in water. It is the basic bait for shrimp stocking. It has the advantages of simple method, high nutritional value, labor-saving and low production cost. In a shrimp pond cultivated with a mouthful of basic bait, shrimp fry can be released without bait within half a month.

3. Shrimp seedling transportation and matters needing attention: whether the shrimp seedling transportation is proper or not has a great influence on its survival rate. Dissolved oxygen and water quality are the main factors during transportation. At present, most of them are transported with oxygen in polyethylene bags. This method is light, safe and suitable for all kinds of tools. In a 10-liter polyethylene bag, the fresh sea water is about 1x4, the shrimp fry is about 20,000, then the oxygen is about 3pm, and then the mouth of the bag is fastened. There will be no problem with the transportation time of less than 10 hours. It is safer to put the bag into a carton. The matters needing attention in shrimp seedling transportation are as follows: the seedling water in the seedling pond can not be used in ①, but fresh sea water can not be used, in addition, turbid or polluted sea water can not be used. The time of transporting seedlings of ② should be arranged in the early morning or evening, to avoid the hot sun at noon, and the water temperature of transportation should be controlled close to that of the nursery pond, and avoid exceeding 20 ℃ as far as possible.

4. Matters needing attention when releasing seedlings: pay attention to whether the physical and chemical factors in the shrimp ponds are suitable for the life of shrimp seedlings. Generally, when stocking in April, the water temperature should rise and stabilize at more than 14 ℃, the water depth should be no less than 40 cm, the salinity should be 20 ‰-30 ‰, and the pH value should be 8.6.

5. Daily management of breeding.

① patrolling pond observation. Shrimp fry must be carefully inspected after stocking, and the dynamics of shrimp ponds and the changes of environmental factors must be carefully observed. In case something unexpected happens. The main contents of pond patrol observation are: whether the sluice gate and filter net are tight and intact, whether the activity, feeding and shelling of shrimp are normal, whether the difference of environmental factors is too large, and whether the pond water has a strange smell.

②, change the water. Water exchange is a necessary measure to improve the water quality of shrimp ponds. It can increase the dissolved oxygen in the water, adjust salinity, pH value and water temperature, control the overdensity of unicellular algae, take away metabolic dirt, improve environmental conditions, and increase food organisms. Stimulate shrimp shelling and so on. The specific operation is generally as follows: the early stage (half a month after the release of shrimp fry) is mainly to add water, add a small amount every day until the shrimp pond is full, and then change an appropriate amount of water every day, and the amount of water can be increased to about 30% in the middle and later period. In the later stage, under normal circumstances, it is best to control the daily water exchange at about 50%, so as to avoid excessive differences in environmental factors when the water exchange is too large.

③, take the bait. At present, the bait for shrimp culture in southern Zhejiang is mainly small fish and shrimp with open nets, as well as some compound bait, clams, snails and so on.

According to the research, the feeding equipment of shrimp has the following characteristics: first, the central nervous system of shrimp is simple, it is difficult to form a conditioned reflex, and can not use conditioned stimulation as a feeding signal. Second, the visual range and activity range of shrimp are not large, it mainly depends on the sense of smell to find food. Third, prawns capture food with chelate feet, and the palate foot holds the food before it is torn up by the small palate, and the mouth of the big palate chews into the stomach. Therefore, the bait should have a certain shape, not too fine, not too large. Fourth, the feeding of shrimp changes regularly with the molting cycle. Freshly molted prawns do not eat anything because they have not hardened their bodies. Fifth, when the water quality is good, the food intake of healthy prawns increases with the increase of water temperature within the suitable temperature range of 7 ℃ 32 mol. Therefore, it is necessary to determine the amount of feeding and the size of feed particles according to the above characteristics and the individual size of prawns. Under normal circumstances, more than 70% of prawns should be full or half full one hour after feeding. 4. Compound feed for shrimp due to the continuous expansion of shrimp culture area and the management of fishing moratorium during the breeding period, compound feed must be used instead of natural bait in the process of culture. The advantage of a good compound feed is that it can meet the nutritional needs of prawns at different stages. In particular, the complementary role of protein is used to improve the utilization rate of feed, reduce the pollution of water quality and low quality, reduce diseases, and facilitate preservation and feeding. Therefore, when the disease seriously affects the shrimp aquaculture industry, experts call for the use of compound feed to cultivate shrimp as far as possible, which can play a role in disease prevention and control.

Disease and disease control

The diseases of cultured shrimp can be divided into two categories: biological diseases and abiotic diseases. biological diseases include viral venereal diseases caused by baculovirus, Rickettsia, pathogens, bacterial venereal diseases caused by Vibrio, fungal venereal diseases caused by Fusarium, protozoal STDs caused by Polycondensation worms, worm STDs caused by nematodes, tapeworms, etc. Abiotic diseases, including nutritional venereal diseases caused by malnutrition, environmental factor diseases caused by poor water quality, toxic venereal diseases caused by harmful chemicals, etc.

The occurrence of shrimp disease is quite complicated. although the existence and invasion of biotic and abiotic venereal factors is the direct cause of shrimp disease, it is not necessarily morbidity or even death in the presence of pathogenic organisms. It also depends on shrimp health and environmental conditions, so protecting the environment and strengthening the physique of shrimp can play a preventive role.

At present, the disease epidemic during shrimp culture has become a global problem. It has caused a devastating blow to the shrimp aquaculture industry, but so far no effective control methods have been found.