How are artificial triploid catfish bred?
The ordinary animals we see every day, such as pigs, chickens, dogs and fish, generally contain two sets of genetic carriers - chromosomes - which in genetics are called diploid. Normal sexual reproduction is the process of diploid replication. Fish, like other animals, go through the process of gestation - growth - reproduction of offspring during their lifetime. In pond culture, once fish grow to maturity they use the nutrients taken in from feed to develop their gonads, that is, the testes or ovaries; during this period bodily growth stops, which is unfavorable for obtaining the best farming returns. During the egg-bearing and spawning period, some fish turn rather gray and lusterless in body color, which lowers their value as market fish. In addition, we also hope that valuable small fish species can grow larger. Modern biotechnology has made it possible to solve these problems. Scientific and technical personnel at the Pearl River Fisheries Research Institute used fish chromosome set manipulation techniques to turn the diploid, small, high-quality fish - the catfish (scientific name Clarias fuscus) - into a triploid fish. This artificial triploid catfish grows 28% faster than the natural diploid catfish, is uniform in size and bright in body color, and its gonads do not develop or develop poorly, so all the feed given is used for body growth and weight gain, and the market quality of the grown fish is superior to that of the diploid. At present, this fish is undergoing pilot-scale production, and it is expected that fry will soon be supplied to farmers.
The farming method for artificial triploid catfish is the same as for ordinary native catfish, and the feed is completely identical as well. Generally, fry of 3-5 cm in size can be stocked in the pond. In the early stage, better feed can be used as appropriate, such as the natural food "bloodworms", peanut bran, and eel feed mixed with wheat flour, so that the fry grow quickly and enter the rapid growth stage. If the pond where the fry are stocked has been pre-cultivated with abundant "water fleas" (zooplankton), the survival rate of the stocked fry will be higher. During the farming process, pay attention to changes in pond water quality, replenish fresh water in good time, keep the water quality excellent, and reduce the occurrence of disease.
The pond for raising triploid catfish need not be too large; 200 sq m to 2000 sq m (3 mu) is sufficient. An appropriate quantity of bighead carp (Aristichthys nobilis), bream-like silver carp (Hypophthalmichthys molitrix) and tilapia, etc. can be polycultured to make full use of the water body's productivity.
According to experiments, the disease resistance of triploid catfish is stronger than that of diploid catfish; under the same rearing conditions the disease incidence is lower, and especially at the two susceptible stages - the fry stage and the 50 g body weight stage - they showed relatively good resistance. If fish disease does occur, there is no need to worry; simply treat it according to the usual treatment methods and drugs used for raising diploid catfish. But what matters most is still careful routine management: observe frequently, replenish fresh water in good time, keep the environment favorable, and regularly or irregularly mix bactericidal drugs into the feed for prevention - prevention is more important than treatment.
In short, the economic returns from raising triploid catfish are certainly much higher than from raising ordinary native catfish.