The artificial reproduction method of eels is basically the same as that of other domestic fishes, but because of the small amount of eggs carried (200-600 grains/tail), a larger number of parents is needed. When selecting and cultivating parent fish, it is necessary to select individuals of different lengths to ensure that the ratio of male to female is coordinated. The main technical points of eel reproduction: 1. Selection of parent eels parent eels can be obtained from the parent eel cultivation pool, or from the market to buy, as long as the parent eels are well selected, artificial reproduction can be successful. The female eel is about 30 centimeters long and weighs 150-250 grams. Mature female eels have an enlarged fusiform abdomen. Smaller mature female eels have an obvious transparent band around their abdomen, and the outline of the egg grains can be seen outside the body; touching the abdomen with your hand can make you feel soft and elastic, and the genital pore is red and swollen. The male eel should be 200-500 grams in weight. The male eel has a small abdomen, with bloodstained spots on the belly surface and reddish-swollen genital pores. If you squeeze the abdomen with your hand, you can squeeze out a small amount of transparent semen. Active spermatozoa can be seen under a high power microscope.2. Oxytocics and oxytocics can be used to promote luteinizing hormone-releasing hormone analog (LRH-A), chorionic gonadotropin (HCG), carp pituitary gland (PG) to promote labor. One injection of LRH-A is more effective. The amount of injection depends on the size of the parent fish, 15-50 grams of female eels, 5-10 micrograms of LRH-A per tail injection, 50-250 grams of female eels, 10-30 micrograms per tail injection. The selected parent eels were wrapped in a dry towel or gauze to prevent sliding, and then injected in the thoracic cavity to a depth of no more than 0.5 cm, and the amount of LRH-A injected was no more than 1 ml. Twenty-four hours after the female eel was injected, the male eel was then injected with 10-20 micrograms of LRH-A per tail. The injected eels are placed in an aquarium or net box for temporary rearing. The water in the box should not be too deep, generally 20-30 cm can be, change the water once a day. Water temperature below 25 ℃, 40 hours after the injection every 3 hours to check the same batch of parental injection, the effect time is often inconsistent, so it should be checked until about 75 hours after the injection. The method of checking is to catch the female eel, touch its abdomen and move it from front to back, if you feel that the eel eggs have been free, then it indicates that ovulation has begun, and artificial insemination should be carried out immediately. 3. The female eel will be taken out of the artificial insemination to begin to ovulate, and one hand will hold the front of a dry towel, and the other hand will squeeze the abdomen from the front to the back, and some of the eels will be able to successfully extrude the eggs, but most of the female eels will be clogged with cloacal cavity, and at this time, we can use a small scissors to move the cloacal cavity to the back, then we can use a small scissor to move the eggs into the back. Scissors can be used to cut 0.5 to 1 centimeter in the cloaca, and then the eggs will be extruded again, 3 to 5 times in a row, until empty. Egg containers can be used glass jar or porcelain basin, the eggs squeezed into the container, immediately kill the male eel, take out the sperm nest, take a small portion of more than 400 times under the microscope to observe, such as sperm activity is normal, you can use scissors to cut the sperm nest into pieces, put into the extruded eggs, mix thoroughly (artificial insemination of male and female ratio, depending on the amount of eggs, generally 3 to 5:1), and then add the Ren's solution of 200 ml, place 5 minutes, and then add water to wash away the sperm nest debris and blood stains, into the incubator static water incubation. 4. artificial incubation incubator can be selected according to the number of spawning glass tanks, ceramic pots, aquariums, small mesh boxes, etc., as long as the management of the appropriate, can be hatched eel fry. The specific gravity of eel eggs is greater than water, in the case of natural reproduction, the eel eggs rely on the eel spit out foam floating on the surface of the water hatchlings, artificial reproduction, can not get this floating eel egg foam, eel eggs will sink to the bottom of the water. Therefore, the water should not be too deep, generally controlled at about 10 centimeters. Artificial reproduction fertilization rate is low, unfertilized eggs disintegrate and easily deteriorate the water quality, should be removed in time. When incubating in closed containers, be careful to change the water frequently, and the difference in water temperature should not exceed 5℃ when changing water. When the eel eggs hatch, the oxygen consumption is different at different stages of embryonic development. In the water temperature of 24 ℃ under the condition of determining the oxygen consumption per 100 eel eggs per hour, cell division stage for 0.29 mg, blastocyst stage for 0.46 mg, the proto-gut stage for 0.53 mg. In the process of embryonic development, the more to the later, the greater the oxygen consumption, therefore, in the tank, pots in static water incubation, to increase the number of water changes. 5. eel egg maturity and fertilization of the identification of the eel eggs just output eel eggs yellowish and reddish-orange, specific gravity is greater than the water, non-sticky. After the egg absorbs water and expands, the diameter is 3.8~5.2 millimeters, weighing about 35 milligrams. The better matured eggs were rounded after absorbing water, forming obvious egg gap, with clear boundary between yolk and egg membrane, yolk concentrated at the bottom, and the embryonic disk was clearly visible after absorbing water for 40 minutes. Eggs that are not well matured are not rounded after water absorption, the yolk and egg membrane are not clearly delineated, and opaque mist can be seen in the egg, which can only be used as an indicator of egg maturity, but cannot be used as an indicator for identifying fertilized eggs. A well-matured but unfertilized egg forms a pseudoembryonic disk and undergoes cell division. Therefore, whether an egg is fertilized or not is observed up to the protocorm stage. Due to the rich yolk of eel eggs, untreated eggs are difficult to see clearly with the naked eye and microscopic examination, and must be used to identify the liquid transparent and then do the microscopic examination. Identification liquid formula is: formalin 5 ml, glycerol 6 ml, glacial acetic acid 4 ml, distilled water 85 ml. Incubation water temperature of about 25 ℃, 18 to 22 hours after artificial insemination, observe the egg fertilization. At this time, the eel eggs were taken out and immersed in the identification solution for 3 minutes and then observed under the microscope, if the blastocysts extended downward and the proto-gut was formed, it could be judged that the eggs had been fertilized. Under the same conditions, the neural plate is formed about 60 hours after fertilization. Egg emergence usually occurs 5 to 7 days after fertilization. Most of the eggs emerge head first and a few tail first. The yolk sac is larger in newly emerged fry. The length of the emerging fry varies according to the size of the eggs, usually 1.2 to 2 centimeters. After 4 to 7 days in the incubator, the yolk sacs basically disappeared, and the body length of the young eels generally reached 3 to 3.1 cm, which can be put into the fry cultivation pool cultivation. In recent years, the Sichuan Provincial Academy of Agricultural Sciences Aquatic Research Institute Ke Kauntao, Zhao Yunfang, etc. to carry out experimental research on artificial reproduction of eels, and achieved good results, the main technical experience is as follows: (1) the source of the parent eel and the selection of parent eels: parent eels are purchased from the farmer's market. The ratio of male to female is 2-3:1. In the reproductive season, the mature female parent eels are soft and bulky in the lower abdomen, the ovaries are obvious, the abdomen is light orange-red, slightly transparent, and the genital pore is red and swollen. The male parent eels are all over 50 centimeters in length. (2) spawning time, method and spawning mode: spawning time is June 2 to July 16, the water temperature is 23 ~ 27 ℃. *** Hypnosis 6 batches of parent eels. Hypnobirthing drugs used chorionic gonadotropin. The abdomen of the female parental eels catalyzed for spawning was obviously softened, and the genital pore was red and swollen and gradually opened. Under the same conditions, the unhypnotized female eels did not have the above changes, could not produce their own eggs, and could not squeeze out the egg particles. Under the same conditions, the unhypnotized female eels did not have the above changes, and could not produce their own eggs, nor could they squeeze out the egg particles. Generally, the eggs are collected by hand (squeezing or cutting open the abdomen to get the eggs), and a few eels can be self-produced. Male eels are dissected to extract semen for dry insemination, and the fertilization rate is about 43%. (3) Incubation: Fertilized eggs are orange-red in color, with specific gravity greater than that of water, non-sticky, and the diameter of the egg after water absorption and expansion is about 4.5 mm. The egg membrane is translucent. Using static water incubation method. The water temperature is 27～30℃, the incubation time is 9～11 days, and the hatching rate is 57.2%. (C) embryonic development of fertilized eggs 1. Eggs of eels have a diameter of 3.3-3.7 mm, and the weight of the eggs is about 35 mg. The yolk is uniform, and the egg membrane is colorless and translucent (see Figure 1-1). Twelve to 20 minutes after fertilization of the egg, the fertilization membrane lifts up, forming an obvious egg gap, at which time the egg diameter increases to 3.8 to 5.2 mm and protoplasmic flow begins. 40～60 minutes after fertilization, the obvious embryonic disk can be seen (see Figure 1bis), from the fertilization of the egg until the early stage of protozoa, the animal pole of the egg are facing upwards.2. Egg cleavage period under the water temperature of about 25 ℃, the eel egg fertilized about 120 minutes after the first egg cleavage occurs, by the meristematic cleavage of the formation of two equal splitting sphere (see Figure 1bis). The second egg cleavage occurs about 180 minutes after fertilization, perpendicular to the surface of the first egg cleavage, forming four equal split balls by meristematic cleavage (see Fig.1-4), the third egg cleavage occurs about 240 minutes after fertilization, parallel to the surface of the first cleavage, and forming eight roughly equal cells by meristematic cleavage (see Fig.1-5), and the fourth cleavage occurs about 300 minutes after fertilization, perpendicular to the surface of the first cleavage, forming sixteen cells (see Fig. 1-6), about 360 minutes after fertilization, 32 cells of approximately equal size are formed, arranged in a single layer (see Fig. 1-7), thereafter, the division continues, through the multicellular stage, and develops to the blastocyst stage about 12 hours after fertilization (see Fig. 1-8). 3. Proto-intestinal stage, with the continuation of the cleavage of the egg, the cells of the animal pole are getting smaller and smaller, and the elevated blastocysts are gradually becoming lower and lower and are buried along the surface of the yolk to the animal pole, the proto-intestinal stage starts (see Fig. 1-8). The protogastric stage begins (see Figure 1-9). At about 18 hours after fertilization, the animal pole cells descend into the early protogastric stage, forming an annular elevated embryonic ring. At about 21 hours after fertilization, the zooepidermal cells underpack to 1/3 of the egg, and the embryonic shield appears (see Fig. 1-10). At about 35 hours after fertilization, the animal pole cells are encapsulated up to 1/2 of the egg and the neural embryo is formed (see Fig. 1-11). At about 44 hours after fertilization, the embryo develops into a large yolk plug (see Figure 1-12). At about 48 hours after fertilization, the embryo enters the period of the small yolk plug (see Fig. 1-13). At about 60 hours after fertilization, the blastopore closes (see Fig. 1-14).4. Neural embryo stageAt the same time as the protocoel is underpacked, the cells of the animal pole begin to invaginate, and at about 21 hours after fertilization, the embryonic shield is formed and thickened, forming the proto-neural pole (see Fig. 1-10). Thereafter, as the protocoel underpacks, the neural plate develops and elongates, and the neural groove is formed when the tail buds begin to grow at about 65 hours after fertilization (see Fig. 1 no. 15).5. Organogenesis (1) Formation of the heart: at about 60 hours after fertilization, the heart is formed in the form of a thin, straight, tubular heart (see Fig. 1 no. 16), and it begins to beat slowly, at about 45 beats per minute, with no red blood cells in the blood. Thereafter, the heart gradually expands at both ends and is divided into auricles and ventricles (see Fig. 1, no. 17), which in turn appear to be curved. About 90 hours after fertilization, an S-shaped heart is formed, with a heartbeat of about 90 beats per minute, and the blood is red in color due to the presence of red blood cells. (2) Growth of the tail bud: After the closure of the blastopore, the tail bud begins to grow. At about 77 hours after fertilization, the tail end forms a bend towards the front (see Figure 1-18). After about 95 hours after fertilization the tail stretches toward the back (see Fig. 1 no. 19) and continues to elongate. (3) Brain and eye development: around 65 hours after fertilization, the head of the neuroblast expands to form three brain vesicles, anterior, middle and posterior, after which the rhombic ventricles can be seen (see Fig. 1 no. 20). Optic vesicles appear on both sides of the anterior ventricle at about 85 hours after fertilization (see Fig. 1 no. 21), and crystals form at about 100 hours after fertilization. (4) Movement of muscles: At about 65 hours after fertilization, the muscles begin to tremble slightly. With the progress of development, the trembling becomes shaking, and by about 95 hours after fertilization, the embryo can turn freely within the egg membrane. Fig. 1 Schematic diagram of the development of the eel embryo 1. unfertilized egg 2. 40-60 minutes after fertilization, the embryonic disk is seen 3. about 20 minutes after fertilization, the first oocyte cleavage 4. second oocyte cleavage 5. third oocyte cleavage 6. fourth oocyte cleavage 7. fifth oocyte cleavage 8. blastocystic embryo period 9. protogastric initiation period 10. embryonic shield emergence 11. formation of the neural embryo 12. period of large yolk pegs 13. period of small yolk pegs 14. embryonic foramen closure 15. formation of neural groove 16. heart formation 17. heart divides into auricular ventricles 18. tail buds form 19. tail extends posteriorly 20. rhombic ventricles and pectoral fins appear 21. optic vesicles appear 22. young fish (5) onset and degradation of the fins: at about 69 hours after fertilization, the pectoral fins are formed (see Fig. 1bis 20) and flap continuously, at about 90 times per minute, while growing with the tail buds at about 94 hours after fertilization. At about 94 hours after fertilization, a distinct fin membrane forms on the dorsal and caudal parts of the embryo (see Fig. 1 no. 19). The pectoral fins and fin membranes are richly networked with microvessels, and blood is seen to flow regularly. By the time the yolk sac is close to disappearing, the pectoral fins and fin membranes also degenerate and disappear. (6) Incubation period: Before hatching, the egg membrane gradually softens and thins, and the embryo rotates vigorously within the egg membrane. When the water temperature is 22℃, 327 hours after fertilization (288～366 hours), the fish breaks the membrane and comes out. The body length of the young fish is usually 12-20 mm when it comes out of the membrane, and the yolk sac of the newly de-membranated young fish is quite large, with a diameter of about 3 mm (see Figure 1-22). Littlenecks can only lie on their sides on the bottom of the water or swim in a struggling position. (7) Litter stage: 24 hours after hatching, the body length of the fish is 16-21 mm; 72 hours after hatching, the body length of the fish is 19-24 mm; 120 hours after hatching, the body length of the fish is 22-30 mm; 144 hours after hatching, the body length of the fish is 23-33 mm, and the length of the jaw is about 1.2 mm. At this time, the yolk sac has completely disappeared, the pectoral fins and the fin membranes on the back and tail have also disappeared, the pigment cells cover the back of the head, making the fish body blackish brown, and the youngsters can swim rapidly in the water and start feeding on silk worms. (d) Artificial breeding of eel fry cultivation eel fry cultivation pool should be used in a small cement pool, pool depth of 30 ~ 40 cm, the upper edge should be higher than the ground 20 cm or more, in order to prevent the rainwater pool caused by the escape of seedlings. The pool should be equipped with inlet and outlet, and covered with plastic netting. Pool area is generally not more than 10 square meters. The bottom of the pool with soil about 5 cm. Add cow dung or pig manure 0.5 to 1 kg per square meter. Water depth of 10 to 20 centimeters. It is best to lead the silk earthworms into the pool, the surface of the pool stocked with root-rich water hyacinth. The eel fry can be cultivated in the pool 5-7 days after the film comes out, and 100-200 eel fry are put in each square meter. The best bait for the openings is silk earthworms, which can also be fed to zooplankton, or animal bait such as minced fish. Eels have self-cannibalization habits, do not mix the size when stocking. Usually pay attention to water quality management, often filling new water. After 1 month of feeding, young eels can generally grow to about 8 centimeters. By the end of the year each square meter can be out of young fish about 100 tails, each tail body length up to 15 cm, weight 3 grams or so, then can be transferred to the adult eel pool feeding. Sichuan Academy of Agricultural Sciences Institute of Aquatic Research on the cultivation of eel fry is: baby eel yolk sac fast disappeared, began to feed bait, the first batch of eel fry with two kinds of bait, a group of feeding animal bait, a group of feeding with bait, after 19 days of feeding, the results of feeding animal bait a group of eel maximum individual length of 4.7 centimeters, the smallest length of 3.9 centimeters; and feeding with bait a group of eel maximum individual length of 3.9 centimeters, minimum of 2.9 cm, and a group of eel maximum individual length of only 2 cm. The maximum length of the group fed with animal bait was 4.7 cm and the minimum length was 3.9 cm. Then the baby eels were transferred from indoor to outdoor small pool rearing, 8 days later check, young eels grow well.