Normally, farmers will conduct “test seedlings†prior to investment, that is, take a small amount of shrimp seedlings from the seedlings in advance, put them in pots filled with pond water, and observe the survival rate of shrimp seedlings after a day and night. Estimate the number of shrimp into the pond. In fact, the pond water in the basin does not represent the real situation of the entire shrimp pond. The data obtained from this basin is also not accurate. How to more accurately determine the survival rate of shrimp seedlings 2 days to 15 days after entering the pond, there are the following two common practices in the industry.
Method 1: Make a cage. The mesh can be slightly smaller than the size of the shrimp seedlings. Place it in the tuyere under the pond. It is 0.5m from the shore and sinks. It is best to put it into the pond 3 days to 4 days in advance. About 100 shrimp hatchlings are placed in cages when they are cast. Because the water in shrimp ponds circulates, the environment in the cage is almost the same as the environment in the pond. The situation of shrimp in the whole pond can be estimated by the number of shrimp in the cage. It should be noted that the nets of the sand nets of the cages are attached to the microalgae, blocking the exchange of water flow and requiring 2 days to 3 days for cleaning. Affected by this, the number of shrimp seedlings in cages will be about half to 10%.
Method 2: Use a dip net to scrape the shrimp along the edge of the pond. If the pond has a seedling density of 50,000/mu, generally 20 to 30 can be scraped. This is a normal phenomenon. It is recommended to scrape several more. Comprehensive considerations. In the early stages of the shrimp movement, the whole pond swims. Usually there are few shrimps in the upper stream, and there are many shrimps in the lower outlet. After two days to three days of adaptation, the shrimp will leave the shore and travel to the area 1.5 meters to 2 meters away from the shore. , so the results of different observation positions are different. In addition, the status and constitution of scraping shrimps can be combined to prove the symptoms. If the shrimp seedlings have blemishes, swimming ponds, etc., or the body is whitish, intestines are empty, hepatopancreas are vague and other symptoms can be determined. Onset, survival rate decreased.
It is suggested that the above two methods be used together, but only one can be estimated.
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