Choosing good fingerlings is the basis for cultivating quality seedlings. The winter and spring season is a good season for the selection of fish species. The following technical points must be taken into account when selecting fish species: Fish age: The age of fish is approximately: 2 years for carp, 3 years for carp, 5~6 years for grass carp, and 6 for carp ~7 years, carp 1 year. Male and female sex differences in sexual maturation age, - male fish than female sex maturity of about one year earlier. Weight: The first-time mature weight of the female: 1 kg of carp, 4-6 kg of whitefish, 6-7 kg of grass carp, 12-16 kg of herring, and 0.2 kg of carp. The body weight of males when they are sexually mature is generally less than that of sexually mature females. Sex ratio: The sex ratio of male and female fish is better than 1:1~l:1.5. According to the number of seedlings to determine the matching population of fish. Qualitative: The identification of male and female fingerlings is mainly based on secondary sex signs. Such as: male grass carp pectoral fin in front of a few rays with star tracking, pectoral fins narrower and longer, more than half of the distance between the base of the pectoral fin to the basal fin, abdomen scales smaller and sharp; and female grass carp without tracking, short chest ray, abdomen scales Big and round. The male and female fish have abdominal ray rays, a star-chasing star on the lid, and a rough feel in the hands, while the females are opposite. Several ray rays in front of the male's chest have cavities, while the females have few cavities or cavities, and the fins are shorter than the males. Male squids have knife teeth in front of the pectoral fins and females have no teeth. Male pectoral fins are larger and longer than females. Physique: The selected species of fish on the basis of ensuring that the parents have the typical characteristics of the species, and the relative distance between the species, also requires that the fish shape is robust, plump, colorful, no injury, no pests, and strong vitality.
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