What are the efficient management measures for fry aquaculture?
Feeding the feed
According to the nutritional needs of fry at different growth stages, rearing is divided into the following three stages:
1. First stage: from day 1 to day 7 after the fry are stocked in the pond, with a total length of 0.7 to 1.2 cm, fed with fresh pig blood, using 500 grams of pig blood per 10,000 fry per day, mixed with water and splashed along the pond edge, fed in 3 portions (1 portion each at 9:00, 14:00 and 18:00).
2. Second stage: from day 8 to day 14 after the fry are stocked in the pond, with a total length of 1.2 to 2.0 cm. Feed crushed peanut bran (40 to 60 mesh granules); peanut bran has an aromatic flavor that attracts fish, has high nutritional value, and can also fertilize the water. The daily amount is 500 grams per 10,000 fry, scattered dry over the whole pond, fed in 2 portions (1 portion each at 10:00 and 17:00).
3. Third stage: from day 15 to day 50 after the fry are stocked in the pond, with a total length of 2.0 to 5.0 cm. Crush compound feed with a protein content of more than 32% into 10 to 20 mesh granules; the daily feeding amount is about 8% of the total weight of the fry, fed in 2 portions (1 portion each at 10:00 and 17:00). Feeding should adhere to the “four fixed” principles, and the feeding amount should be adjusted according to actual conditions.
Adding water in stages
Adding water in stages to meet the requirements of fry at different stages for activity space, water quality, nutrition and other conditions is an effective measure to increase the survival rate and growth rate during fry rearing. The specific method of operation is: stock the fry in shallow water, that is, when the fry are stocked in the pond the water depth is about 0.6 m; afterward, according to the water color and the growth of the fry, add water once every 4 to 5 days, adding 10 to 20 cm each time, and finally stabilize the water depth at 1.2 to 1.5 m. When adding water, it must be filtered through a fine mesh net to prevent wild and miscellaneous fish from entering the fry pond with the water.
Daily management
Walk around the pond once each morning and evening, carefully observe the water quality, the activity of the fry and their feeding situation, promptly remove sick fish and dead fish, and carry out an examination immediately; if the fry are confirmed to be diseased, necessary prevention and control measures should be taken. In addition, check the embankment for leaks and whether the drainage outlet is intact, and pay attention to preventing escape.
Timely pond separation
After about 25 days of rearing, when the fry reach a total length of 2.5 to 3.0 cm, seine netting, selection and pond separation for sparse rearing should be carried out in a planned way; otherwise, the survival rate of fry rearing will be low. This is because fry grow rapidly during the rearing stage, and uneven individual development will occur, along with the phenomenon of big fish eating small fish, especially when the feeding amount is insufficient. The author has had such an experience: 500,000 fry with a total length of 2.5 cm were stocked in a pond, and because the ponds were not separated in time, after 30 days of rearing only 100,000 fry with a total length of about 5.0 cm were obtained, and the rearing survival rate was only 20%.