The broodstock can be selected from broodstock, either naturally or artificially. The breeding period is from May to September and the peak period is from May to June. The female broodstock should have a body weight of about 25 grams, and the second-instar fish have more eggs. Female sex gland development is better characterized by more abdominal enlargement, shunting big breasts and round blunt; male fish should choose about 20 grams, shattering mastoid longer than the tip.
Broodstock with well-developed gonads can be used directly for spawning or spawning in spawning pools (in spawning pipelines). The gonads with a gonad maturity of 3 to 4 months are kept in a holding pool and fed to benthic diatoms collected from natural beaches. The depth of the pool is 20 to 30 cm, and 50% of the water is changed every day.
Artificial oxytocin
Oxytocin using human chorionic gonadotropin (HCG) and luteinizing gonadotropin analogue (LHRH-A), single or mixed use, pectoral fin base injection or dorsal fin base injection. The females were injected twice, at intervals of 16 or 24 hours; the males were injected once and injected half as much per gram of body weight as females.
At a water temperature of 22 to 24°C and a salinity of 25 to 27 ‰, the egg matures 24 hours after the second injection. High-dose HCG and mixed hormone (HCG+LHRH-A) had the best effect of ovulation. The male fish was injected only once and synchronized with the second shot of the female. After spawning, the new fish should be divided into male and female stocks and inflated and changed water every day. The water temperature is 19 to 21°C, the effect time is 39 to 58 hours, the water temperature is 26 to 29°C, and the effect time is 14 to 16 hours. After 12 hours of injection, the females were regularly examined for egg development. If the mature eggs were found to flow out, the male testis was taken and semi-dried artificial insemination was performed.
The specific operation process is: dissecting the ovary, cutting the ovaries bag into a dry plastic pot (or extruding the egg without dissecting), and then taking the male fish nest to pulverize or cut it into several pieces and putting it into the pot to mix with the egg. The ratio of females to males is 2:1. The fertilized eggs are then poured into a bucket filled with clean seawater, and the eggs are agitated evenly over the pre-prepared sieve. The egg is attached to the sieve and the net can be hung in the hatching pond.
Artificial pipeline
Artificial pipes are fired with ceramics in the shape of a cylinder with a diameter of 10-20 cm, and the upper and lower pipes can be dismantled. Put the artificial pipe into the spawning tank with a water depth of 20-25 cm. The gonads with good gonad maturity were paired into the pool and each brood was placed on the broodstock. Feed sludge with benthic diatoms daily and feed on bait stations.
The time for spawning of large salamanders in the pipeline is from midnight to midnight. Check once a day in the morning and check 2 to 3 pipelines at a time. If spawning is found, check all the eggs and move the attached eggs into the incubation pool. More than 10,000 eggs can be obtained for tuber production. Artificial spawning pipelines can induce broodstock pairing and natural spawning, but spawning is not concentrated. Therefore, multiple small nursery ponds should be used. Tests have shown that raising the water temperature in the spawning pool can promote gonad maturation, which is an effective measure to obtain concentrated spawning.
incubation
The hatched egg or spawning pipelines are directly hung in the hatchery cement pool and inflated, or placed in the Cage to be inflated and incubated, all can achieve a high hatching rate with an average hatching rate of 50-60%. During the incubation period, 50% of water is changed every day, or micro-flowing water throughout the day.
The optimum incubation water temperature is 26-28°C, and the incubation water temperature should not exceed 30°C. At a water temperature of 26.5 to 29.2°C and a salinity of 25 to 27 ‰, the larvae of the fish film emerged for about 87 hours.
On the fourth day of hatching, most of the larvae have already broken out of the membrane. At this time, the egg-catching nets and pipes can be taken out. Hatched larvae can be left in the hatchery pond for cultivation, or they can be moved to nursery ponds for cultivation.
Larval rearing
The newly hatched larvae are about 2.5 mm in length. Nursery pond stocking density of 5000 fishes per cubic meter. On the second day of hatching, the larvae began to open. On the fifth day, the larvae had a total length of 3.5 to 4 mm. The yolk sac disappeared. There was only one small dot left in the oil globules. There were 13 melanin spots on the ventral edge and they started feeding. Feeding should begin on the third day of hatching.
The rotifers were fed twice a day and the amount of rotifers in the ponds was calculated before feeding and then the rotifers were added. The rotifer density in nursery ponds is around 5 per milliliter. The juveniles began metamorphosis around the age of 35 days, and they entered the larval stage. The scales gradually became full, with 8 rows of melanin horizontal stripes on the side and back. At this time, Artemia nauplii should be fed in an appropriate amount. From the late juvenile to the early juvenile stage, the diet was dominated by animal diets; the young juveniles had a total length of about 2 cm before and after the 45th day of age, were transferred to diatoms, and were fed to the mudflat to collect benthic diatoms. At this point you can go out of the pool.
During nursery, the cultivation water is sand-filtered seawater, and the proportion of seawater is too high to be adjusted by fresh water. The proportion of the cultivation water is preferably 1.010 to 1.015. The amount of aeration increases gradually with growth. The amount of water changed every day is 1/5 to 1/2.
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