First, grouper ecological habits

Grouper is warm water fish, the main habitat in the rocky reef, submarine caves and voids, coral reefs are carnivorous fish, ferocious, there is the phenomenon of mutual food, especially in juvenile fish stage, individual small often individual large Swallowed out. Usually by fish, shrimp bait, eat, back to the cave or rock reef joints to rest.

Second, grouper breeding habits

Generally speaking, grouper is hermaphrodite, with the growth of a break, the occurrence of sexual conversion. First to become a female, continue to grow into male. Before the gonad is immature, it is difficult to distinguish between male and female. Individuals of sexual conversion vary by species, age and size. Grouper from the beginning of March each year to start laying eggs, females have many characteristics of spawning. Egg is spherical, colorless and transparent, the egg has a ball of oil, is a floating eggs, water temperature at 25-27 ℃ when about 23-25 hours that hatch out, not fertilized eggs are sinking into the sea.

In order to solve the grouper seed, many marine biologists at home and abroad proud of a lot of artificial breeding technology experimental research, and made great progress, mainly in the use of oral methyl testosterone to accelerate the sexual conversion of mature females, Greatly string together the need for natural transformation of the boring stuff. China's Zhejiang Institute of Marine Fisheries (1980) and Zhoushan Institute of Fisheries (1981) on the green grouper artificial insemination and incubation success} Nanhai Institute of Fisheries on the artificial breeding of salmon grouper also made a breakthrough. Many other research units also put it included in the key research topics. Can be predicted, for the development of production to provide a large number of artificial breeding grouper has not far away.

Third, grouper artificial breeding

Before the grouper artificial breeding seed technology has not yet been able to solve the production needs, the breeding of the seed to rely on natural harvest, that catch large stay small (catch large when the sale of goods fish, small catch up, or when the seedlings Kind of sale), therefore, still must understand the Greek: grouper fishing techniques. In Fujian, every year from the "Ching Ming" catch, "Bailu end after the flood season in the beginning of the summer to the summer, so fishermen have" Li summer silver carp under the rock, "said.

And now, with the rapid development of grouper aquaculture, natural seed has been in short supply. Therefore, in recent years, artificial breeding of grouper has attracted people's attention. Now look at the red spot grouper artificial seedling technology

1, broodstock selection and cultivation

Broodstock can be artificially propagated or caught from natural sea areas. Females choose weight 0.5kg ~ 1kg, abdominal swelling and soft; male selection weight 1.5kg or more, clear the abdomen can flow out of the semen. Male and female broodstock with 1: 1 ~ 1: 3 ratio with. In recent years, due to overfishing, the natural sea area of the reproductive population in the male and female sex ratio than the imbalance phenomenon, and breeding under the conditions of cultivation, the breeding of male and female fish, Elderly male individual broodstock is long and costly, so the problem of broodstock selection is that gonadal mature males are not easy to obtain. In order to solve the shortage of male broodstock in artificial breeding, we can use the exogenous sex hormone 17α-methyl testosterone to induce the male and female red spot grouper, which can be converted into female male with reproductive function 3 ~ 4 years earlier, and 17α- Methyl testosterone not only can inhibit yolk formation, but also affect the proliferation and differentiation of ovarian cells. Feeding 50 days of bait for 2 to 4 age fish at a dose of about 5 mg / kg body weight (cumulative dose of 241.3 mg / kg body weight) resulted in 93.5% of the male broth flow rate 81.1%, embryonic development is normal. In order to solve the problem of "sexual transformation" effect caused by uneven feeding of male hormones and the effects of daily feeding and time-consuming, it is also possible to use the method of implanting 17α-methyltestosterone into fish Hormone embedding method to induce early change of grouper. 17α-methyl testosterone can be implanted once in the age of 3 to 7 years old mature red spot grouper fish, 50 days to 90 days after the females into male fish, so that grouper "sexual change" The process is 5 to 6 years earlier. The fertilization rate of fertilized eggs with their semen was 73%, the hatching rate was 97%, the development of larvae was normal, and the purpose of artificial breeding was achieved. Under the same treatment conditions, the female sex fish had a "sexual change" time shorter than that of the younger fish and were more susceptible to the release of the modified male. Therefore, in the artificial breeding should try to choose the older, the larger female female degeneration treatment, the effect is better.

In order to solve the problem of artificial reproduction of mature male mature fish, but also the application of ultra-low temperature cryopreservation of semen, frozen in liquid nitrogen tank for 2 months after the semen still has the equivalent of fresh vitality, does not affect the artificial breeding Effect. The effect of artificial reproduction depends largely on the maturity of the broom gonads, so in the induction of spawning, to strengthen the cultivation of broodstock, promote gonadal development is essential. In the indoor cement pool in the accumulation or temporary grouper fish, through artificial cultivation, daily water and sewage, broodstock without hormone production can be natural fertilization, can obtain high quality fertilized eggs.

2, oxytocin

Choose a good female broodstock, with a fine plastic tube or digester from the production of the ear hole inserted about 3cm ~ 5cm deep suction of the egg, placed on the carrier plate, observed under the microscope its maturity, easy to separate eggs, egg yolk, Full, egg diameter 0.3mm ~ 0.5mm, plus transparent fixation after the nuclear has been biased to the animal, the maturity is better. Male broods gently press the abdomen with a little sperm outflowers mature well. Grouper less semen, check the maturity of males do not squeeze too heavy. The oxytocin has four kinds of carp pituitary, chorionic gonadotropin, luteinizing hormone releasing hormone analogue and LRH-A + PG mixture.

Female with PG10mg / kg body weight to 12mg / kg body weight or LRH-A60ug / kg. The above dose is generally divided into two injections, the first injection volume of the total amount of 2/3, the interval between the two times the water temperature 25 ℃ ~ 26 ℃ when the time is about 24 hours. Male broodstock injection dose is half of the female, both in the female injection at the same time the second time. Injection of water for the 0.6% sodium chloride solution, the oxytocin dissolved or made of suspension, the amount of injection for each of the broodstock injection 1ml ~ 2ml for the degree.

3, artificial insemination and natural fertilization

Artificial insemination of red spot grouper should adopt dry method. Broodstock injection of the second needle oxytocin after 10h ~ 13h to spawning, from top to bottom gently pressed the female abdomen, the mature eggs poured into the sterilized white porcelain bowl, repeated 5 times to 6 times after Broodstock gently put back into the broiler pool. Then the same method will be used to squeeze the male semen into the egg bowl of white porcelain bowl. Grouper sperm rarely, even squeeze 5 times ~ 6 times a total of 1ml ~ 2ml, but enough. After the last squeeze finished, that is, with the disinfection of seawater immersion clean feathers bowl of eggs and semen evenly, about 1min ~ 2min after adding a small amount of disinfectant water, continue to stir for 5min after dumping in the small basin , Add sterile seawater gently stir well, standing for a moment.

All fertilized eggs are floating in the middle of the water, dead eggs or unfertilized eggs at the bottom. Wash the fertilized eggs with disinfectant seawater to remove excess sperm to avoid fertilization and then move the fertilized eggs into the incubator.

Artificial insemination, should avoid direct sunlight, so as not to kill sperm. As the grouper is a batch of spawning fish, there are several successive spawning reproductive characteristics. If it is for the broodstock to create spawning in the natural spawning fertilization of the environmental conditions, you can avoid the artificial insemination often appear when the egg is too mature or not mature enough defects, but also can reduce the fishing and squeeze, squeeze the semen caused by the Broom damage. Therefore, it can also be used to strengthen the cultivation of grouper fish, to promote the secretion of hormones, no injection of oxytocin and natural spawning fertilization, which won the high quality fertilized eggs, raising the survival rate of larvae, reducing the rate of deformity. Natural spawning method is superior to artificial oxytocin. Sprinkler suitable water temperature 25 ℃ ~ 27 ℃, sea water salinity 32 ~ 35, pH7.8 ~ 8.5, spawning area of 20 square meters, water depth of about 1.5m, the top of the pool with shading shade, water flow 40L / min ~ 50L / Min.

4, hatching

Grouper production of floating eggs, hatching should be in the loop incubator or hatchery tank. Hatching eggs when the egg density of 50 eggs / L sea water ~ 100 eggs / L sea water, water flow in order to make the eggs or larvae floating for the degree. Hatching water must be fresh, subject to sand filter and ultraviolet light sterilization. Water temperature maintained at about 25 ℃, salinity 30% to 33%, and remain stable. Incubation process need to moderate inflation, inflation is too large or too small are not good, so that the amount of dissolved oxygen in the sea to maintain more than 5 mg / l. Incubate as much as possible to remove dead eggs, to prevent deterioration of water quality. Red spot grouper and blue grouper eggs in the above conditions, since the spawning fertilization after 24 hours can be hatched fry.