2, specifications and quality. The size of the library fish should be large and the constitution should be robust. This is the basis for high yield. Clam and salmon 11.55-13.22 centimeters; grass carp 13.20-14.85 centimeters; cod and carp 6.60-8.25 centimeters. Can also be based on local conditions of production of seedlings, the size of the reservoir, the degree of damage to ferocious fish and other flexible. Where the production conditions are good, the reservoir is small, and the fierce fish have little harm to the reservoir, the species may be smaller. On the contrary, there is a requirement for length specifications. The physical factors must not be ignored. Good quality fingerlings can improve the survival rate. The quality index of high-quality 13 cm fingerlings is (tail/kg): squid 44, squid 42, grass carp 48, and herring 50.
3, with the proportion. In order to make full and reasonable use of various types of natural food resources in the reservoir, the proportion of various types of fish that are put into the reservoir should be suitable. As the main cultured fish, cockroaches and codfish should account for 70%-90% of the total number of fish species to be fed (60%-70%, and 30%-40%). Other fish stocked with stocking, such as herbivorous fish such as grass carp, sea bream, and bream, may account for 10% to 30% of the number of fingerlings released. How many of these fish are stocked, on the one hand, depends on the corresponding feed resources in the library, and on the other hand, on the basis of the supplementary groups that naturally reproduce in the stocks.
4, density. According to the extent of the bait resources in the library. Generally, it is necessary to maintain a dynamic balance between the fish population in the reservoir and the natural food. In general, the stocking density of the species in the extensive crude culture reservoir is determined by referring to its nutrient type. Stocking densities (tail/mu/year); eutrophic 110-160, moderately nutrient 80-110, oligotrophic 50-80. Of course, reasonable stocking densities need to be adjusted depending on various fish growth rates and annual production.
1, species. The amount of plankton in the reservoir is large, and the diet of the filter-feeding fish is rich, while in the filter-feeding fish, the growth of the cockroaches and cockroaches is fastest, the individual is large, and the source of the seed is wide. It is the main stocking target. In order to make full use of other bait resources, omnivorous grasshoppers, oysters, and herbivorous fish species such as grass carp, clams, and oysters, which mainly consist of benthic animals, can also be stocked. Note that it is not appropriate to put more fish as the main fish.