Detailed Explanation of Key Technical Points for Spring Broodstock Cultivation

After the beginning of spring, water temperatures gradually rise. Especially during the pre-spawning stage in March and April, fish activity increases, development accelerates, and food intake rises accordingly. This stage is an important period for gonadal development of broodstock. Practice has proven that the quality of spring broodstock cultivation is the key to the success or failure of artificial breeding of Chinese carp. Therefore, the following points must be well managed:

1. Feeding. Grass carp broodstock are mainly fed grass and concentrated feed. Depending on the availability of grass, generally grass is fed in the morning and concentrated feed in the afternoon, both on fixed feeding platforms. In early spring when green feed is scarce, grass carp can be fed some wheat, sprouted grain, lettuce or vegetable leaves. Later, they are fed ryegrass, aquatic plants, etc. The feeding amount is 2%-4% of fish body weight, with the criterion being that the feed is consumed within 2-3 hours. Black carp must be fed a certain amount of animal-based feed, with live snails and clams fed once every 2-3 days. Silver carp and bighead carp are fed powdered concentrated feed at 1%-2% of fish body weight daily. One month before induced spawning, if the water quality is relatively fertile, feeding can be stopped.

2. Fertilization. Silver carp and bighead carp broodstock ponds are generally managed mainly by fertilization, applying organic fertilizer once every 7-10 days, at 100-150 kg per mu each time, by broadcasting method. If organic fertilizer is insufficient, some chemical fertilizer can be applied appropriately, once every 5-7 days, at about 5 kg each time. Fertilization should be moderate to prevent excess. When fertilizing, it should be flexibly adjusted according to the fertility level of the pond water. Silver carp broodstock pond water is best when it is oil-green or yellow-green, while bighead carp broodstock ponds are best when tea-brown. Maintain transparency between 35-40 cm. Fertilization can be stopped half a month before induced spawning.

3. Regulating water quality. After the beginning of spring, because the pond has been through a winter, the physicochemical factors and plankton conditions in the water are not conducive to energy conversion. Therefore, before starting feeding and fertilization, it is best to replace half of the broodstock pond water and maintain a water depth of 1 m. Silver carp and bighead carp broodstock ponds are flushed once every 20 days, adding 3-5 cm of water each time; grass carp broodstock ponds are flushed once every 10-15 days, adding 5-10 cm of water each time. One month before induced spawning, flushing can be done once every 2-3 days. The flow rate during flushing should not be too rapid, to prevent broodstock from excessively consuming energy by swimming against the current.

4. Pond inspection and disease prevention. Inspect the pond once at dawn and once at dusk every day, checking whether fish are gasping at the surface, whether food intake has increased or decreased, and whether the water is too fertile or too lean. Problems should be solved promptly when discovered. When water temperature rises, disinfect the feeding area of broodstock ponds once every 10-15 days, using about 1 jin of bleaching powder per pond, dissolved in water and broadcast over the feeding area and its surroundings.