Detailed explanation of rapid fish fry cultivation techniques in summer

Summer is a very important season for fish fry cultivation. Good cultivation measures can promote growth, strengthen physique, improve disease resistance, provide large-sized and robust superior fry for adult fish farming, and achieve increased production, income, and efficiency. Summarizing the experience of recent years, rapid fish fry cultivation in summer should achieve the following points:

1. Regulate the water environment. As the saying goes, "@#@233@#@ first raise the water; when the water is good, the fry are strong." In ponds that have previously cultivated fry, due to long-term aquaculture, sludge accumulates, water quality gradually ages and deteriorates, dissolved oxygen decreases, feed organisms decrease, and pathogenic microorganisms and harmful substances increase, which is unfavorable for the growth and development of fry. Therefore, every possible effort should be made to improve the water environment for fry growth. First, frequently replace with new water and discharge old water, adding 30cm of fresh water each time and discharging 20-30cm of old water, to keep the water body relatively stable. Second, appropriately fertilize the water quality. Generally, every 7 days apply 200kg/667m2 of fermented manure water; or fertilize once per mu and add new water once, so that the water body is nutrient-rich, plankton is stable, and transparency is about 30cm. Third, regularly disinfect the water quality. Every half month, splash water mixed with 15kg/6677m2 of quicklime or 1g/m3 of bleaching powder. Quicklime adjusts pH, releases nutrients, and improves water quality; while bleaching powder kills bacteria and viruses. Used alternately, the effect of preventing and treating fish diseases is remarkable.

2. Adjust fry size. Fish of different sizes should be raised in separate ponds, and different species should be reasonably mixed. For those mainly cultivating silver carp and bighead carp fry, 20%-30% grass carp fry should also be included, and the ratio of silver carp to bighead carp fry should be 3-4:1. If mainly culturing bottom-dwelling fry such as tilapia, carp, mud carp, crucian carp, and white pomfret, then 80% should be bottom-dwelling fry and 20% should be silver carp and bighead carp fry. Emphasis is placed on stocking filter-feeding silver carp and bighead carp fry, mainly to filter excess plankton, reasonably regulate water quality, reduce diseases, and prevent water eutrophication. Stocking density should also be determined according to specific conditions such as pond environment (whether water source irrigation and drainage are easy), area size, water depth, fry size, and feed supply. The general practice is: for water depth above 1.5m, about 5000 fry can be raised per 667m2; if they are tilapia, carp, or crucian carp fry, 6000 can be stocked per 667m2.

3. Strengthen water quality regulation. Summer weather is changeable and water temperature is high. To prevent pond water temperature from being too high, deep water should be added. Second, new water should be added and old water discharged, generally changing the water once every 7 days; pay attention to keeping the water quality fresh. In short, it should be flexibly controlled according to the condition of the pond water. Keep it fertile, lively, tender, and refreshing.

4. Pay attention to reasonable nutrition. In summer, attention should be paid to supplementing fresh feed for grass carp, blunt snout bream, etc., such as duckweed, lesser duckweed, green grass, and green vegetable leaves; for black carp, mostly add crushed snails and clam meat, etc.; silver carp and bighead carp should also be appropriately fed crushed wheat bran, corn bran, soybean powder, etc., and an appropriate amount of green feed should be added. Feeding should be timed, fixed-point, fixed-quality, and quantitative, so as not to waste, while also allowing the fish school to eat enough and gain fat, ensuring that the fry reach a relatively large size. The daily feed amount should preferably account for 3% of the pond fry amount. The four major Chinese carps and tropical and subtropical fish such as mud carp, tilapia, white pomfret, and catfish should be fed at 9-10 a.m. and 15-16 p.m. Before reaching a certain size, do not stop feeding too early, so as not to affect growth.