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1. Identification and selection of male and female frogs: Male and female bullfrogs that reach sexual maturity are clearly different in appearance. The tympanic membrane diameter of the male bullfrog is significantly larger than the diameter of the eye; for the forehand, the inside of the forehand has a well-developed marriage tumor on the inside of the thumb, and the reproductive season is more pronounced; the skin of the throat is golden yellow, and the reproductive season is darker with a pair of ribbon-like cysts. A loud voice can occur. The diameter of the tympanic membrane of the female bullfrog is slightly smaller than the diameter of the eye; the thumb of the forelimb does not have a marital tumor; the skin of the throat is grayish-white, with black markings and no vocal sac.
The pros and cons of pro-frog quality are directly related to the reproductive effects and economic traits of offspring. Therefore, the frog must be carefully selected. Pro-frogs should be disease-free, injury-free, physically strong, and well-formed. Male frogs should be selected over 2 years of age, the skin of the cyst is golden yellow, marriage tumors are obvious, the weight is about 300 to 400 grams; female frogs should choose 3 years of age, abdomen enlargement, soft, elastic, weighing about 400 to 500 grams .
The time to choose a frog is best to be completed in November before the winter and finish in March at the latest. Pre-winter selection of good frogs, preferably male and female separately, until the beginning of the second year in early April and then combined male and female frog feeding. It is necessary to strengthen the feeding and management during the overwintering period so as to ensure safe winterization and a good constitution after winter. Starting in mid-March, the frogs should also adopt intensive cultivation to promote the development of their gonads.
2. Male-male ratio: The proportion of male-female-friendly frogs is, in principle, 1:1. If the proportion of male frogs can be appropriately increased, the male frogs will have less effect on reproductive performance. However, there must not be too many male frogs, and too many male frogs will cause each other to compete for female frogs, affecting the normal mateship of male and female frogs, and even causing frog casualties. Frogs are generally stocked on a standard of 1 pair per 5 square meters of water.
3. Spawning and fecundity: When the water temperature rises above 18°C, the male frog starts estrus, mainly as frequent buzzing and chasing female frogs. In general, a female frog is estrus 15 days later than a male frog, and the female frog's estrus shows irritability. The frog is attached to the male frog and obeys the male frog. When the bullfrog is cuddling, the male frog is on the back of the female frog and holds the frog's ankle in her hand. Hugs for a short time, up to 2 days long. When the female frog lays eggs, the mature eggs in the uterus are continuously excreted through the vent holes due to the contraction of the abdomen and the assistance of the male frogs, and usually the two eggs are discharged side by side from the excretory hole. At this time, the male frog clings to the back of the female frog and ejaculates at the same time. The sperm and egg are fertilized in vitro. The general spawning time lasts 10 to 20 minutes. Bullfrogs require a quiet environment when spawning, and the idlers should be prohibited from entering or exiting during the spawning season so as not to interfere with spawning and discontinue production.
The amount of spawning of bullfrogs is related to age, individual size, nutritional conditions, and ecological conditions. The frogs weighing 300 to 500 grams range in egg production from 10,000 to 50,000 eggs, and the egg production per gram weight frog ranges from 15 to 109 grains.
Second, the hatching of eggs
1. Oviposition: After the bullfrog spawns, the fertilized eggs cannot stay in the spawning pool for a long time. Generally, eggs should be collected 20 to 30 minutes after spawning. At this time, the egg membrane outside the fertilized egg has fully absorbed and expanded, and the fertilized egg can be transposed in the egg membrane so that the animal of the fertilized egg faces up and the plant pole faces downwards. A grayish black egg mass can be seen on the water surface. It's a good time to pick eggs. In order to ensure the timely collection of eggs, in the spawning season, it is necessary to strengthen the inspection of the spawning pool in order to promptly discover the egg mass. In the evening when the male frog buzzes frequently, it is particularly necessary to observe the situation of the frog pair. Generally, the place where the frogs are held in the night before is the place for spawning the next day. This can be a purposeful discovery of egg masses to avoid omissions.
When picking eggs, use scissors to cut off the grasses that adhere to the egg masses. Do not pull hard pull to avoid breaking the egg membrane and affect hatching. The eggs removed are quickly transferred to the hatchery. It is best to put 1 egg hatch into 1 hatching pond. If the hatching pond has a large area and multiple egg masses must be placed, eggs from the same production should be put in order to ensure synchronized hatching. This will prevent hatching in the hatching ponds of different sizes due to successive hatches and affect the stocking of the fish.
2. Incubation density: The density of hatching is directly related to the hatching rate. When the hatching tank is used for hydrostatic incubation, only 6,000 eggs can be laid per square meter; if micro-flowing water or cages are used for hatching, the hatching density can be increased to 8,000 to 10,000 eggs per square meter.
3. Environmental conditions required for hatching: The incubation of bullfrog eggs is closely related to water temperature. The water temperature required for hatching is 20-31°C, and the optimum water temperature is 25-28°C. The suitable pH of the hatching water is 6.8-8.5, and the acid water has less oxygen, which will affect hatching, and the egg membrane will be softened and the egg will be flattened, resulting in the death of the broken egg. Incubation water should have sufficient oxygen. Generally, the dissolved oxygen level in water should not be less than 3 mg/l. Below 3 mg/l, it will cause eggs to die.
4. Management during incubation: The hatchery is exposed to direct sunlight at noon, the temperature of the water is high, and the temperature is low at night or on rainy days, resulting in a large temperature difference between day and night, affecting the hatching rate. The hatchery should be shaded above the hatching tank and covered at the hatching tank at night to keep the temperature stable. Embryonic development should always be observed during hatching, and the dead eggs should be removed in time to prevent water from spreading. After hatching, as the egg membrane dissolves, a large amount of oxygen is consumed in the water, which results in lack of oxygen in the water and deteriorates the water quality. At this time, proper water flow or water change should be taken.
Newly hatched quails have poor swimming ability and often inhale on the wall of the hatching vessel or on the grass, and should be less agitated so as not to affect the rest and survival rate.
Bullfrog breeding, egg hatching
First, the breeding of bullfrogs