How to Carry Out Selective Breeding and Breed Conservation in Jian Carp Farming

Any superior breed, if selective breeding and breed conservation are neglected, will often lead to breed degradation, reduced yield and deterioration of other traits. Jian carp has stable genetic traits and can, through within-breed reproduction, pass the superior traits of this breed on to its offspring. However, different carp breeds easily interbreed and become mixed, individuals within the same breed also differ, and the living environment can have a considerable effect on the traits of a breed. Therefore, attention must be paid to selective breeding of superior stock: according to the breed's standards, fish with good traits in all relevant respects should be selected as broodstock for rearing and allowed to reproduce offspring. In the selection of Jian carp, attention is mainly paid to three indicators: growth rate, body shape and body colour. Growth rate is mainly shown in two aspects, weight gain and body length gain, especially weight gain, that is, under the same rearing conditions, selecting the largest individuals from the same batch of fish; body shape also directly affects market sales and price, and at present people generally prefer the long-bodied type. For Jian carp, superior individuals should be selected whose ratio of caudal peduncle length to caudal peduncle depth is equal to or greater than 1, and whose ratio of body length to body depth is greater than the population average; for Jian carp body colour, individuals that are blue-grey and rather whitish should be selected. As for selection methods, they are often based on the characteristics of Jian carp at different developmental stages and combined with farming measures, carrying out four rounds of screening: summer fry, winter fingerlings or spring fingerlings, reserve broodstock and pre-spawning broodstock. Summer fry screening is mainly culling, with growth rate as the main indicator; winter fingerlings or spring fingerlings are mainly hand-selected, with attention to growth rate and body shape, eliminating red carp; reserve broodstock focuses on a comprehensive evaluation of overall traits; pre-spawning broodstock must be re-examined and arranged by male-to-female ratio and pairing. For breed conservation, attention should be paid to production specialisation, that is, a unit or fish farm had best produce only one kind of carp. Any unit producing Jian carp should no longer produce other carp, and still less produce hybrid carp; attention should be paid to rearing in dedicated ponds, strictly preventing mixing with other carp; attention should also be paid to the renewal of broodstock, as the optimal age for using broodstock is limited, generally 3-5 years for females, and it needs to be constantly replenished from reserve broodstock. At the same time, to prevent possible inbreeding and genetic drift in small populations within the fish farm, new purebred broodstock should be regularly introduced from the original breed farm or research institute.