Causes and countermeasures of low recapture rate in jellyfish culture

1. The reasons for the low recapture rate of jellyfish cultured in ponds

1. The selection of culture ponds is not standard. First, the water quality of the pond is poor, the area of a single pond is too small or the water depth is too shallow. Second, the old ponds, which have been cultivated for many years, have thick silt, small slope ratio, incomplete pond cleaning and many harmful organisms. Some ponds have raised clams, clams or Sinonovacula sinensis, but failed to thoroughly dry the beach, clear the pond and disinfect before breeding. There are plenty of shrimp ponds in continuous reclamation areas, with different breeds and specifications. Coupled with the serious infiltration of the pond, the sun beach is not complete. The pollution of influent and drainage in the middle of the outer dike is serious. Third, the influent and effluent conditions are poor, and the neap tide in shrimp ponds in some reclamation areas can not change water. Fourth, there is a lack of fresh water sources, and the proportion of seawater is on the high side.

two。 Poor fodder cultivation and insufficient bait. The feeding activities of jellyfish are continuous day and night, and the food is digested after 4 to 5 hours after a full meal. The daily food intake of jellyfish was 6000 at 20mm, 100000 at 70mm, 260000 at 110mm and more than 2.9 million at 230mm. Its growth is unusually rapid, the weight of 3mg dish larvae, after 2 months of growth, can reach more than 10kg, weight gain more than 3 million times. The growth rate of jellyfish is closely related to the food organisms in the water.

3. Seedling release time. Improper specification and density or poor technology of transporting and throwing seedlings result in low survival rate of seedlings and affect the recapture rate.

4. The technology of aquaculture management can't keep up. First, the blocking measures are not effective, and the soft umbrella top of the jellyfish is easy to rub and damage with the pool wall, causing the jellyfish to grab the beach and die. Second, water quality management technology. Raising jellyfish first, the level of water fertility and physical and chemical factors should meet the growth needs of jellyfish, but many aquiculturists only know that the fertility of water body is related to bait, ignoring the three elements of "fertilizer, activity and coolness" of water quality.

2. Countermeasures to improve the recapture rate of jellyfish culture in ponds

1. Select standardized ponds, thoroughly clear ponds, sun beach, disinfection, and implement reasonable blocking measures. Purse seine or plastic sheet should be added at the water depth of 0.5m on the shore and supported by bamboo pole to prevent the death of jellyfish.

two。 Before seedling release, it is necessary to do a good job of fertilizer and water and increase the plankton biomass in the water to ensure the bait biomass at the initial stage of seedling release. The concentration of fertilizer and water should be appropriate to prevent the water quality from deteriorating and affecting the survival rate of seedlings. Using chicken manure to fertilize and water must pay attention to thoroughly fermenting chicken manure for 7 ~ 8 days before it can be used. In the hot season, it is best not to use chicken manure to prevent water pollution. The water quality should be tested before seedling release, mainly including water temperature, salinity, planktonic biomass, pH value and so on. At the same time, attention should be paid to the water temperature and salinity of nursery ponds and nursery ponds, and the gap between them should be adjusted to a minimum through the nursery room, so as not to affect the survival rate of stinging seedlings due to the excessive gap.

3. The selection of excellent seedlings with strong, disease-free and large size is a prerequisite for successful culture.

4. Do a good job in seedling transportation and release, and improve the survival rate of seedlings. The time to release seedlings should be in the morning or evening when the weather is better, preferably without wind or direct sunlight. When transporting seedlings, oxygen, shading and ice should be added to prevent heating from affecting the survival rate of transportation. After the seedlings are transported to the edge of the pond, you should not rush to put the seedlings into the pond. You should first untie the mouth of the bag and observe its vitality, then pour the seedlings into a larger container and add some water from the pond. Let the seedlings adapt for a period of time (10-20 minutes) and then put them into the pool. When releasing seedlings, you should use a small boat to transport the seedlings to the middle of the pond and sprinkle them evenly into the pond. the operation should not be impatient and should be carried out slowly to prevent damage to the seedlings.

5. Do a good job in daily aquaculture management, especially water exchange and artificial fertilizer work.