How to improve the survival rate of seedlings through reasonable fertilization and timely ponding?

After many years of fish farming, a large number of plankton eggs are stored in the pond silt, and there are 1 million to 2 million rotifers per square meter in the pond, of which more than 99% are buried in the silt, which only occupies the surface of the silt. After the fry pond is filled with water, the biological community undergoes a natural succession, and diatoms and chlorella appear that are small and multiply quickly.

1. Plankton change pattern after quicklime pond clearingThe changes in the palatable bait organisms of the fry from the lower pond to the summer flowers with a total length of 30 mm are generally rotifers and rotifer nauplii - small cladopods - large cladopods - copepods. The fry are at the peak of rotifer reproduction in the pond, not only the fry just out of the pond have sufficient palatable bait, but also have abundant palatable bait at all stages of development in the future. From a biological point of view, the time for fry to be released into the pond should be 7 to 10 days after the pond is cleared, when the pond is at the peak of rotifers.

Second, in order to make the fry in the peak period of rotifers, the key is to determine a reasonable fertilization time. If fertilization is too late, the number of rotifers in the pond is still small, the fry will not grow well because of the lack of a large number of palatable bait after going down to the pond, if the fertilization is too early, the peak period of rotifers has passed, a large number of large cladoperans appear, the fry not only can not eat, but the cladopera and the fry compete for dissolved oxygen, space and bait, and the fry greatly affect their survival rate due to the lack of palatable bait. In order to ensure that after the application of organic fertilizer, rotifers can multiply in large quantities, in the production of often sprinkle 1 kg of crystal trichlorfon to kill large zooplankton, and then apply organic fertilizer.

If the fry fail to arrive on time, 1 kg of crystal trichlorfon should be used 2 to 3 days before the fry go to the pond, and some organic fertilizer should be added in an appropriate amount.

Third, the fry should be put into the pond in a timely manner, in addition to the bait conditions should be suitableThe biology of the fry itself is also something to consider. Studies have shown that the suitable time for carp and grass carp fry to go down to the pond is 12 to 24 hours after the appearance period of the waist point, and the fry have hatched for 4 to 5 days. If you go down to the pond too early, the fry have weak activity ability, and it is easy to sink to the bottom and die, and if you go down to the pond too late, the yolk sac has been completely absorbed, and the fry can not obtain enough open bait resulting in nutrient deficiency, which affects the survival rate of fry cultivation.

It must be emphasized that the safe water temperature of the fry in the pond should not be lower than Celsius, and the water temperature of the fry in the pond is 18 to 23 degrees Celsius. If the water temperature is too low, the proliferation of zooplankton such as rotifers is too slow, and it is difficult to fertilize and water, which is not conducive to the feeding and growth of fish fry.

If the fertilization time is too late, the number of rotifers in the pond does not meet the requirements, and the fry will not have enough food after the pond, and the growth will not meet expectations.

Fish fry cultivation is mainly based on soybean milk bait, supplemented by fertilization, and it is necessary to go to the pond at the peak of the rotifer season of the fish fry, and do not miss the opportunity.

Indirect fertilization or drip irrigation can improve the efficiency and nutrients of watering, and the absorption of substances is very good.