The second sex character of freshwater oysters is not obvious throughout life, and it is difficult to distinguish between male and female. Mature females, in acidic water, are darker in color than males and have dark red chest, pelvic, and anal fins. The ovaries are clearly visible on the abdomen, and the anus is prominent on the outer edge of the cloaca. This is due to ovarian congestion. Pressure results. Male fish are also recognizable in mature seasons. In acidic water, the lower half of the abdomen or lateral line is brightly colored with silver and white, the abdomen is flattened, the cloaca is closed, and there is a line on the body surface.
In order to accelerate the gonad development of the broodstock, drugs can be used for artificial ripening. The current practice is to start ripening for 2nd-introduced broodstock. When the 2nd instar broodstock came out of the greenhouse after wintering, the ripening hormone was injected once every 2 weeks. The weight of the broodstock per kilogram was RES 2mg, plus LRH-2A 2μg, mixed and made into injections, and the freshwater turtle was injected abdomen. It has been proved that the gonads can be matured earlier and the effect of oxytocin production is very good.
Second, the choice of broodstock
Infuse broodstock before urinating, but avoid broodstock injuries. The broodstock with smooth body surface and no injury was selected for oxytocin production. Female abdomen should have obvious ovary outlines, and the vent holes should have reddish and slight protrusions. Generally, the abdomen does not require softness because the intercostal bone in the abdomen is thick and the abdomen is always rigid and rigid. This is related to the four major fishes. It is completely different. Check the ovary with an egg digger to check that the granules are round and uniform in size. The oocysts are placed in the nucleation fluid to separate the eggs. The nucleus eccentricity is above 50%. Selecting such a female has a better oxytocin effect. For males that are first breeding, it is very difficult to squeeze out the semen by squeezing the abdomen. Only 10% to 20% of the males can squeeze out a small amount of milky white semen. These males can choose to use as oxytocin, as long as the oxytocic drugs are used properly. There is also a good oxytocin effect.
Third, artificial aphrodisiac spawning
The artificial production of freshwater oysters is performed using the spawning pool of "Four Home Fish" aphrodisiac. Area of ​​about 40 ~ 50, can be placed in broodstock 20 groups, broodstock injected into the pool after the injection of aphrodisiac, keep flushing to stimulate, female and male can mating their own eggs.
According to the reproductive endocrinological integration of fish and the metabolism of protein peptide hormones, the reproductive physiology of freshwater turtles is simultaneously regulated by both body fluids and nerves. Tests have shown that using drugs such as DOM or RES, without using the pituitary gland, as long as a small amount of LRH-A or HCG is used, the effect of hormones can be maintained until the end of ovulation, so that the freshwater turtle can reproduce 100% of the oxytocin production. Rate and emptying rate to get satisfactory fertilization and hatching effect.
The optimum water temperature for artificial aphrodisiac spawning is 26°C to 30°C, and the effect time for broodstock injection is 6 hours to 8 hours. Females and males have obvious estrus and are chasing fiercely. Before brooding, the brooding fish whisper in the water that they are slightly in the water. When they hear the sound, they can retrieve fertilized eggs in the spawning pool. It is worth noting that if the water temperature in the pool reaches 32°C or more, the fertility rate of freshwater turtle spawning is very low, generally only about 10%, and most of them are deformed embryos, which is not desirable in production.
IV Artificial Incubation of Fertilized Eggs
Since the eggs of the freshwater oysters expand after absorbing water and appear semi-floating in the running water, hatching may be performed using an artificial hatching loop or hatching tank (cylinder) of the domestic fish. Because the expansion of the egg membrane is not large, the proportion of eggs is larger than that of the four eggs. Therefore, the flow rate must be increased during hatching so that the eggs can be uniformly turned in the incubator and the hatching rate can reach over 90%.
The second key to artificial hatching is to remove the sword leeches in the water for hatching. Due to the fertilized eggs of freshwater turtles, the hatching time in the incubator is very long, and it is also obviously different from the characteristics of the “Four Home Fish†hatching. When the water temperature is in a good condition of 28°C to 30°C, it takes about 120 to 130 hours from the inoculation of the fertilized egg to the incubator to the emergence of the intestine at the lumbar point (inflated inflated), so the incubator cannot bring the sword blisters. Because spawning ponds and incubators in the incubator will accumulate more and more quickly, they will cause great harm to fry and eggs. There is currently no way to remove drugs from the swords and leeches brought about by the water's incubation and desalination. The freshwater lice are very sensitive to the trichlorfon drugs and cannot be used. In order to prevent the sword leeches from entering the spawning ponds and incubators during production, an effective method is to use 120-mesh net cloth to make an open pontoon and filter the hatchery water with satisfactory results. Otherwise hatching will lead to failure.
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