1. Selection of broodstock and quality of seedlings After the shrimp producer of China has solved the problem of gonadal development during the artificial breeding of white shrimp (Penaeus vannamei), most large-scale individuals from the cultivated commercial shrimp are used as breeding materials. The use of broodstock, due to the broodstock intensive breeding techniques and feeding conditions, the majority of the bred broodstock quality can not meet the requirements for the production of high quality shrimp seedlings, so the poor quality of seedlings is inevitable. In addition, to ensure the quality of seedlings, it is also very important to select SPF-free Penaeus vannamei as a broodstock, which can not only block the vertical transmission of the virus, but also reduce the occurrence of virus disease during the cultivation period. As a result, the production of SPF shrimp is an important guarantee for the stable development of the South American white shrimp aquaculture industry. Although early broodstocks were purchased from SPF broodstock in the United States or Brazil, there was also a problem of germplasm degradation, which usually should be replaced after 3-5 generations. However, due to the low seedling prices in recent years, most of the nursery farms are living in and out, replacing them. Broodstock has become a very real problem. Strengthening broodstock breeding and improving the quality of larvae are also important measures for the development of high quality shrimp seedlings. During the nursery process, the high-quality larvae have a fast metamorphosis and are not susceptible to disease. Even if the disease recovers quickly, the survival rate is high. Poor quality larvae have delayed metamorphosis, abnormal metamorphosis, and susceptibility to disease. Once they become ill, the survival rate drops significantly. Therefore, attention should be paid to the research and improvement of broodstock breeding techniques. 2. Treatment of the nursery pond wall and adjustment of aerated amount In order to ensure the fresh water in the nursery, it is necessary to constantly change the water and aerate the oxygen, but frequently changing the water and violently flushing not only increase the production cost, but also easily cause larvae. The stress response. This is because changing the water and inflating will cause the pool water to flow. The flow of water will drive the collision and friction between the larvae and the pool wall. This is a harm to the young, weak and weak larvae. After the damage to the body surface, the disease resistance of larvae decreases, and it is vulnerable to invasion and infection by foreign pathogens. Therefore, it is very necessary to trim the pool wall and keep it smooth and reduce the amount of aeration. The ideal method is to treat the special paint for water production on the pool wall of the nursery pond, so that the treated pool wall becomes smoother, so as to reduce the damage to the larvae and be easy to clean. At the same time, the size of the aeration must be properly adjusted according to the abnormal progress of the larvae. In the period of no-litter larvae and zoea larvae, the amount of aeration must be small, and the water surface can be microwaved. As the larvae grow, with the addition of residual bait and organic matter in the water, the amount of aeration in the larval shrimp period should gradually increase to the surface of the water. The adjustment of the aeration rate can reduce the injury of the shrimp seedlings, which is beneficial to the improvement of the quality of the shrimp seedlings. 3. Regulation of light intensity The effects of light during the larval rearing process cannot be ignored. From nauplii to larvae of juveniles, larvae have obvious phototaxis. If the light intensity in the nursery is inconsistent, it will lead to uneven distribution of larval density, thus affecting the use of bait, and the density of local larvae High affects the normal feeding and growth of larvae. Some sources pointed out that under strong light irradiation, the larvae may stop feeding, and the deformity rate and death increase. Therefore, covering the plastic film above the nursery pond to maintain low light and scattering light in the nursery will reduce the occurrence of larval clustering. 4. Operation at the time of emergence During the breeding process, each inappropriate operation will affect the larvae, especially if the improper operation during the emergence period will directly affect the survival rate of the shrimps after they are sold. The correct method is to use the siphon method to drain about 1/3 of the pool water first, and maintain a certain water level in the pool, so as to avoid the impact of the water stream on the shrimp, which will help reduce the incidence of the shrimp after the pool is down. The survival rate of shrimp seedlings is improved. In addition, the use of 40-60 mesh sieve to pull net lifting is equally feasible, but the action when the net operation is light and slow, once the capture does not exceed 200,000. At present, this method has been widely adopted in nursery farms in Jiangsu, Zhejiang, and Shanghai. 5. Sludge of larvae In the artificial breeding of Penaeus vannamei, larval adhesion to larvae often occurs. The adherent larvae activity, feeding and metamorphosis are greatly affected. The dirt mainly adhered to the tail bristles and head and thorax appendages of the larvae. Microscopic examination revealed that the stains were mainly filamentous bacteria, ciliates, and some debris. If no effective measures are taken in time after the above symptoms occur, the larvae will soon die if they are unable to clamshell. This phenomenon occurs mostly in the stage of juvenile larvae, and is the most common from pupa I to pupa II. This may be related to the fact that the zoea are in poor physique, malnutrition, deterioration of water quality, and prolonged molting period. After the juvenile metamorphoses into the squid stage, its predation ability increases, its constitution is better, and the frequency of the clam shells increases. The above symptoms are rarely seen. When this phenomenon occurs, warming or changing of water can be used to promote larvae as soon as possible. At the same time, attention should be paid to the water quality treatment and feeding of high-quality bait to enhance the larvae's constitution and increase the larval rearing rate. Author: Wuxi Fisheries College, Nanjing Agricultural University
Oxygen Cylinder Filling System
With PSA principles, ETR Oxygen Cylinder Filling system can produce 93%Â±3% purity oxygen gas from compressed air directly. ETR oxygen cylinder filling system is consisted of Atlas screw air compressor, refrigerated air dryer, compressed air filter, air buffer tank, ETR Oxygen Plant, oxygen buffer tank, oxygen booster, cylinder filling station and HMI control cabinet.
Compressed air is purified through the air dryer and filters to a certain level for main plant to work with. Air buffer is incorporated for smooth supply of compressed air thus to reduce fluctuation of compressed air source. The plant produces oxygen with PSA (pressure swing adsorption) technology, which is a time proven oxygen generation method. Oxygen of desired purity at 93%Â±3% is delivered to oxygen buffer tank for smooth supply of product gas. Oxygen in buffer tank is maintained at 4bar pressure. With an oxygen booster, the oxygen pressure can be to 150bar and fill in cylinders.
Onsite Oxygen Cylinder Filling System
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Hunan Eter Electronic Medical Project Stock Co., Ltd. , http://www.eter-tech.com