Don't Forget to Protect Broodstock During Induced Spawning

Reducing the death of broodstock during induced spawning is an important technical task for fry producers. In production practice we have found that there are two reasons for the death of broodstock during induced spawning: first, the broodstock consumes a great deal of energy during the spawning and reproduction process, and combined with the side effects of the inducing drugs, the body's resistance declines; if the fish is severely injured, various pathogens will seize the opportunity to infect the fish, causing disease and leading to death. Second, the broodstock's constitution is poor, the gonadal development is not good, or the water temperature varies greatly during induced spawning, and the dosage of the inducing drugs is improper (too high or too low), so the broodstock cannot spawn normally or suffers from dystocia, which in turn causes a disorder of its own physiological activities and leads to death. Therefore, in production, emphasis must be placed on the care work before and after induced spawning.

First, attention must be paid to fishing operations, which is an important link in reducing broodstock injuries and deaths. Whether netting broodstock in the broodstock pond or in the spawning pond, the netting operation must be light, quick and coordinated; as soon as the net panel reaches the bank, the net should be closed quickly, and after the net panel is properly covered, the broodstock in the net should be quickly dragged away from the bank to prevent the broodstock from hitting the wall and being injured. On clear days with high temperatures and when the fish transport distance (the distance between the broodstock pond and the spawning pond) is relatively long, it is best to catch fish in the early morning or in the evening, and care must be taken to prevent the broodstock from suffering oxygen deprivation and suffocation injury in the carrying stretcher.

Second, when netting the broodstock after induced spawning from the spawning pond, each fish must be checked one by one. For female broodstock with a swollen abdomen, gently press their abdomen with the hand to help them release the mature eggs already in the abdomen; if the broodstock suffers dystocia because the genital pore is blocked, a sterilized surgical scissors should be used to cut and enlarge the blocked genital pore so that the mature eggs can be discharged from the body; this can prevent the mature eggs from absorbing water and swelling inside the broodstock and endangering it (this is one of the main causes of death of female broodstock after induced spawning). For broodstock with wounds on the body surface, first wipe the wound dry with a degreased cotton ball, then apply and wash with potassium permanganate solution or malachite green solution containing 1% table salt, and then use the fingers to apply sulfonamide ointment or anti-inflammatory ointments such as erythromycin or tetracycline on the wound from the tail toward the head against the direction of the scales; for broodstock with inflamed, red and swollen boils or sores on the body surface, first wipe the lesions dry with a degreased cotton ball, then apply iodine tincture, and then apply anti-inflammatory ointment. For all broodstock after induced spawning, whether injured or not, inject 1 ml of sulfonamide drugs (containing 0.2 g of the drug) per 5-8 kg of body weight, or inject other anti-inflammatory drugs.

The pond where broodstock are stocked after induced spawning must be cleared and disinfected with quicklime. The pond water must be fresh, and a water depth of about 1.5 m is suitable. Within the first month after stocking the broodstock after induced spawning, no organic fertilizer should be applied, and solutions of drugs such as bleaching powder, strong chlorine essence and fish and shrimp safety should be regularly splashed to disinfect and sterilize, prevent and treat fish diseases. About 5 days after the broodstock are put into the pond, feeding begins, mainly feeding the broodstock's favorite rice sprouts, malt, bran cake or compound feed; for grass carp broodstock, an appropriate amount of fresh tender green grass should be fed. Generally, part of the pond water is replaced with fresh water every 3-5 days to regulate water quality, stimulate the broodstock's appetite, enable them to recover quickly and enhance their resistance.