Cultivation of barramundi and barracuda
Barracuda and barracuda are one of the main breeding targets in China's coastal areas. (Mugilidae) The two most common species of fish are characterized by wide salinity, short food chain, rapid growth, and delicious meat taste. It is the main object of "fish" in the south of China and the "maintaining of the sea" in the north, and it is also the main species of polyculture in freshwater fish farming in the coastal sea. It is the most famous fish in the world, such as China, India, the Soviet Union, Japan, Israel and other countries and regions. It is famous for fish farming in the seawater, brackish water and even freshwater aquaculture, which is most popular in the Pacific, Mediterranean and Black Sea coasts. Since the 1950s, China has conducted extensive research and experiments on the biology, artificial propagation, nursery, and aquaculture techniques of barracuda and barracuda across the coast, and has achieved remarkable results. In the 1970s, it broke through the artificial breeding of barracuda and is now capable of mass production. In the 1960s, Taiwan had not succeeded in the artificial breeding of eel, and it has been able to carry out large-scale production so far. In mainland China, the artificial breeding of mackerel is now in many provinces and cities. Successful, but still not as good as Taiwan in scale. Barracudas and barracudas can be monocultured or mixed with freshwater fish. They can effectively use the bait of the pond and increase the yield by about 10% without increasing the amount of feed. They can also be mixed with shrimps and crabs. Greatly improved the economic benefits of water. I. Biology of Barracuda and Barracuda (1) The morphological characteristics Mugil cephalus and Mugil so-iuy belong to the family Carpidae. According to Thomphson (1964), more than 280 species have been reported in the world. Among them, there are many homonymous species, and there are about 70 or so species in classification. There are 28 genera of 7 genera in China. However, in the major works of fish classification in China, the classification of carps is still confusing. At present, there is no controversy about the description and classification status of Sui and Shu. The carp species currently bred in the world include Mugil cephalus, M. capito, M. auratus, M. saliens, and M. tade. ) and barracuda (M.so-iuy). China has the name of the South-Southern North shuttle, which is mainly in the south. In recent years, almost all of the freshwater fish ponds and brackish freshwater fish ponds along the Pearl River Estuary have mainly or mixed carp. Fish, either raised or raised in fish ponds or shrimp ponds. 1. The squid is commonly known as black peony, black pheasant, white eye, aconitum, green head, and barley. Widely distributed in the northeast of China to the southwest coastal area, but to the south of the Yangtze River estuary in the East China Sea, South China Sea as much. Most of the carps are wide-salt and wide-temperature fish, widely distributed in the tropical, subtropical and temperate waters between 42°S and 42°N. Most of the carps are marine fish, and some fish can fully adapt to life in freshwater. The carp body is long, with a cylindrical shape at the front and a flat side at the back. The body length is 4.1-4.8 times the body height. Head and flat, back flat wide, short and wide kiss. The mandibular front has a protrusion and the maxillary depression, and the upper and lower jaws have villous, fine teeth, arranged in a single row. Under the mouth, mouth split. The eyes are large and the fat and eyelids are well developed. The tongue is relatively round and is not free inside the mouth. The boring hole is large, slender, and prosperous. Scales are large, body scales are scales, heads are round scales, and body scales are 38-41. There are two dorsal fins. The starting point of the first dorsal fin is equal to the distance from the snout to the base of the caudal fin, with four hard spines; the second dorsal fin is larger, shaped like the anal fin, with 1-2 hard spines. Anal fin rays 3,8. Caudal fin larger forked. The back is dark and the belly is white. The base of the pectoral fins has a scale. There are often several gray longitudinal stripes on the body side. The body cavity is large and the peritoneum is black. Stomach tubular, pyloric special spherical muscle stomach. The intestine is slender and more curved, about 7 times the length of the body, and the pylorus is large. Big wall and thin. 2. The barracuda is also known as the red-eyed barracuda, and its common names are red-eyed, pointed, and meat sticks. Barracuda is distributed in the Far East and is an offshore fish. China's north coast is distributed, especially in the Yellow Sea and Bohai Sea. The barracuda is shaped like a beak. Its head is short and wide, its eyes are reddish, and its fat and eyelids are undeveloped. It only exists at the edge of the eye. Body side longitudinal scales 41-47. There are two dorsal fins. The starting point of the first dorsal fin is closer to the snout than to the caudal fin. Anal fins are 3,9. The base of the pectoral fin is free of scales and the tail fin is concave. Grayish brown on the back and grayish belly. (B) Habitat habits and barracudas are pelagic fishes in the shallow sea. They live in the coastal estuaries and bay salt and fresh water, and they often inhabit rivers and inhabit freshwater waters. When the temperature of water falls in fall and winter seasons, they enter the deep sea and go winter. . Carp adapts to a wide range of temperature, can live in a water temperature of 3-35 °C, suitable water temperature is 12-32 °C, the optimum temperature for growth is 20-28 °C, lethal temperature is 0 °C; barracuda can endure The temperature range is 0-35°C and the temperature range is 18-28°C, but it is more resistant to low temperatures. The lethal temperature is -7°C. The barramundi have a wide range of adaptability to salinity. Seawater, brackish water and pure water can all live. Carp inhabits more than 30 feet of water, and Israel has successfully farmed the carp in a high salinity (36-145 ft) pond. Barracuda adapts to a salinity of 38 ‰ seawater but grows fastest with salt water. Pelicans and barracuda caught in seawater can adapt to freshwater life quickly as they gradually fade. Larger fish can tolerate changes in salinity. Pelicans and barracudas can live in ponds with low water quality and fertile water. Catfish lived normally in oxygenated water at 2 mg/l in pool water; when it fell to 0.87-1.75 mg/l, it would float; when the oxygen in the pool dropped to 0.52-0.72 mg/l, it would become unconscious even death. For a barracuda with a total length of about 30 mm, water at a temperature of 24-26°C can dissolve in oxygen at a rate of 0.67 mg/l, and when the dissolved oxygen falls below 0.57 mg/l, it begins to die. However, when the water temperature is below 10°C, the dissolved oxygen decreases. To 0.35mg / l can still survive. The suitable pH for the growth of barnyardgrass and barracuda is 7.6-8.5. Pelicans and barracudas are active and sensitive, and juveniles live in groups on the shore. They are more active and swim fast. Carp is irritable and jumps. (3) The food chain of barramundi and barracuda has a low food chain and mainly feeds on organic debris and unicellular algae. The bait for adult fish includes cyanobacteria, green algae, diatoms, plant debris, and sediment. There are also a small amount of copepods, polychaetes, chironomid larvae, clams, and small bivalves. Food composition changes with habitat. Cockroaches and barracudas have a wide range of food habits, and they are omnivorous fishes. Most of them are scraped benthic algae and sedimentary organic debris. The main components of its stomach contents are algae, organics, and non-nutritive coarse sand and mud. Rice bran, bran, cake feed and compound feed were eaten under artificial feeding conditions. (4) The growth rate of barramundi and barracuda is different in different areas and different water areas. In the same area or water area, there are also differences in the growth rate at different stages of development or sex. Cockroaches and barracudas are larger in size. The common catches are 250-400 mm in length, about 1 kg in body weight, 800 mm in size and 4.5 kg in weight. Both fishes grow faster, especially salmon. In the current year, the total length of squid to autumn and winter can reach more than 200 millimeters and over 250 grams; the fish of the second age can reach 300 millimeters and the weight is more than 600 grams; the age of 4-6 can reach 450-550 millimeters and the weight is 1.5-3 kilograms. . It has been reported that the Soviet Black Sea once caught 16-year-old carp, generally weighing 5-6 kilograms, up to 12 kilograms. Carp grows faster than fish in natural fish, especially in saltwater fish ponds. In the use of fish fry breeding in Guangdong in the year, it can generally grow to 0.5-0.6 kg by the end of the year, and individual can grow to 0.75 kg. There was no significant difference in the growth of males and females before the third instar. Barracuda grows slightly slower than salmon. The average body length of barracudas increases with age before 4th instar and grows fastest at 3rd and 4th instars. The growth rate gradually slowed after 5th instar. The highest age in Bohai Sea has been found to be 8 years, with a maximum body length of 72 cm and a maximum weight of 4600 grams. The average length of one-year-old barracuda is about 150 millimeters, and the body weight is 50 grams. The average length of 2 years is about 200 millimeters and the weight is about 200 grams. The third-year-old is about 350 millimeters in length and 500 grams or more in weight. Under the conditions of artificial breeding, the growth rates of barramundi and barracuda vary greatly, which is related to the stocking density and the abundance of bait. For example, the polyculture of freshwater fish ponds, 200 polyculture of polychaetes per mu, up to 400 grams in the year; 300 fish rearing per acre, and only 250-350 grams per year; when stocking 1,400 fish per acre At that time, it only reached 75 grams. If 75 grams of fish are raised for another year, it can reach 800-900 grams. (e) Breeding habits Barracudas and barracudas are generally mature when they are older than 3 years old, and males mature more than one year earlier than females. The age of sexual maturity is closely related to temperature, and waters with high water temperatures mature earlier. The male fish of squid were 2-3 years old, and the female fish were mature at 3-5 years of age, and the body length was 300-500 mm. Barracuda males generally mature at 2 instars, and a large number of them are 3-4 years old. Females begin mature at 3rd instar and mature at 4th instars. The breeding season of carp: 11-1 month in Guangdong; 11-1 month in Fujian, 12 months in December; 11-2 months in Taiwan; 12-1 month in Jiangsu. Barracuda reproduction period: Guangdong is from September to November; coastal Zhejiang is from early April to early May; Fujian is from late April to mid-May; north of the Yangtze River can be extended from late April to early June. The ovary maturation coefficients of carp are: 1-7% not fully developed, and 11-12% when mature. In Xiamen Xinglin Bay spawning group, the maturation coefficient was 19.3% and the minimum was 5.3%. In the mature period in late December, the average female was 15.2% and male was 13.3%. The absolute amount of eggs for squid is about 1 million grains. The females in Xinglin Bay of Fujian Province have more than 200-580 million eggs. Fertility varies in different regions. The fertility of a typical 3rd-age female carp is 64,862 grains/g. The amount of spawning of barracuda varies from a few hundred thousand to four or five million, and the relative amount of spawning is between 0.45 and 740,000 grains/kg. The fecundity is related to the age. The fecundity of the 3-6 age barracudas increases with age. Within 650 mm of body length, the fecundity increases with body length, and the fertility decreases sharply after 650 mm. The position and conditions of the natural spawning ground of the carp are various. Generally, the carp grows in the estuary or harbor. Before the reproduction, the carp has to leave the estuary to lay eggs off the coast (15-40 km from the shore) and spawn. In high-salinity seawater, fertilized eggs develop and hatch, and young fish gradually swim into the mouth of the bay. It is speculated that the reef sea area outside the Lufeng Rock and Huilai Shenquan Harbor in Guangdong may be a spawning ground for carp. Xinglin Bay in Xiamen has many mangrove growths and has also picked up the eggs of the scorpion fish, so it is also an egg-laying farm. It is generally believed that the salmon spawning site requires higher salinity. However, the salinity of surface water in the spawning ground of the Black Sea salmon of the Soviet Union is only 15.56-18.32‰. The majority of salmon spawning is at night, and people are not aware of it. Mackerel has obvious spawning and migration. Some scholars classify them into three types: one is to swim from the lake to the sea; the other is to swim in the sea; the third is to swim in the ocean. The barracuda spawning site is near the coastal estuary port, so there is no long-distance spawning phenomenon. The salinity requirement for spawning is not high. Tianjin Guangang’s salinity can lay eggs at more than 5 inches of barracuda. Spawning is mostly before and after sunrise and sunset. As long as the barracuda is more than 5 ‰ in barren fish breeding in the closed water, it is a favorable condition for artificial reproduction to proceed smoothly. The eggs produced by quail and barracuda are buoyant eggs. The temperature of barracuda at the time of spawning is 15°C or more, and that of carp is 17°C or more. The optimal water temperature for spawning migration of Japanese salmon is 17.1-20.6°C, and the optimum water temperature for salmon spawning in Taiwan is 21-23°C. Second, artificial propagation of artificial breeding of carp has been extensively studied internationally. The research on the artificial reproduction of barracuda and barracuda in China began in the 1960s. Barracuda has undergone more than 10 years of trial and research in many provinces and cities in China, and it has made breakthrough progress by the 1970s. By the 1980s, it has become a productive scale. Some units have been able to breed millions of seedlings a year. The artificial breeding of eel began in the 60s in Taiwan. After more than ten years of hard work, the population has been successful. Currently, it is in a leading position in the world. So far, the artificial production of eel fry in Taiwan has also become a scale. The artificial propagation techniques for barracuda and barracuda are similar, but they differ only in the breeding season. Barracuda reproduces in April-May, and can be carried out at natural temperatures. Carp reproduces in winter and the required water temperature is around 20°C. Therefore, artificial oxytocin, hatching, and seedling breeding need to be warmed indoors. (1) The quality of broodstock fostered by broodstock directly affects whether or not the production capacity will proceed smoothly. 1. The source of the broodstock broodstock comes from three main sources: the sea area, the estuary catch, or the brackish water. The source of Taiwanese fish is from the natural seas in the annual spawning season from December to February of the following year; Since broodstock fishing in natural sea areas is often constrained by a number of environmental factors, fluctuating and encountering many difficulties, later broodstock fish have been raised to more than 3 years of age. Practice has proved that the use of pool culture more than 3 years, maturity of 0.4-4.2% after 3 months of seawater intensive cultivation, the effect of oxytocin than the capture of the natural sea area is better. Barracuda broodstock can be captured from natural sea areas; or directly selected from brackish and freshwater fish (above 3 years of age) above 5 ‰ salinity, intensively cultivated in pre-production one-year special pool; The barracudas cultured in salt water (0.5-5.0 ‰ salinity) gradually increase their salinity by 13-18 越 before and after winter and are intensively cultivated before the birth. Choosing to keep people's use of crickets, barracuda is generally more than 3 in females weighing more than 1 kg, preferably 2 kg or more. Barracuda broodstock is generally selected to remain full of more than 1.2 full-time serving. Barracuda and barracuda are marine fish, and their natural reproduction is carried out in seawater. However, the gonads of barracuda and barracuda are also well developed in waters with very low salinity, even in freshwater. Male sperm can flow, and female ovary can reach. Phase IV, but not the final maturity. Since there is no obvious difference in the appearance of male and female fish, it is difficult to identify and select individual fish (about 1 kilogram) as appropriate when selecting broodstock, because males are smaller than females. 2. Breeding of broodstock (1) The cultivation pond area is 2-3 mu, the water depth is about 1.5 meters, the bottom of mud, the thickness of sludge is 2-10 cm, and the sea and fresh water are convenient for drainage and drainage. The water quality and salinity of the broodstock pool can be adjusted at any time. be quiet. The ponds should be cleaned and disinfected prior to use and then fertilized to feed food organisms. (2) Stocking density is to ensure that the water quality and broodstock have a good ecological environment and normal gonadal development. The stocking amount of broodstock and barracuda broodstock is generally not more than 100 kg per mu; about 40-60 tails/mu. There is a slight difference in the stocking rates of barracuda and barracuda in other provinces and cities and in Taiwan. General male and female press 1:1 as well. (3) Feed quails and barracudas mainly ingest natural grasses and organic debris. During the artificial incubation of broodstock, a variety of artificial feeds are eaten, followed by fertilization to cultivate the natural food in the pond, which can be fertilized with feces such as chickens, ducks, pigs, and cattle. The feed uses cakes, wheat bran, wheat, rice bran or compound feed. The best feed contains about 35% crude protein. In the growing season, the daily feed is about 5% of body weight. (4) The day-to-day management of day-to-day management is a key task for broodstock breeding. (a) Flowing water and regulating water quality Regular flow of water to regulate water quality Maintaining fresh water can increase appetite, accelerate growth and, more importantly, promote gonadal development, and is an important measure for broodstock breeding. The quality of water is “fat, live, and coolâ€, with a transparency of about 35 cm and dissolved oxygen above 3 mg/l. (b) Nutrients require large amounts of nutrients for reproduction and growth of egg cells. Eggs need to accumulate abundant substances for embryonic development. Therefore, nutrition must be enhanced and the proportion of protein must be increased. Vitamins (especially vitamin E) must be added. Minerals. (c) Light illumination has a close relationship with the development of the gonads of carps, especially the length of light of carp. Guo Qinming (1971, 1973) tested the maturation of Hawaiian carp-induced ovarian development and pointed out that shortening the illumination time (6 hours of light/18 hours of darkness) can effectively stimulate the ovary in the primary oocyte stage to reach maturity in advance. At a water temperature of 17-26°C, a constant 8 hr light/18 hr dark light cycle is effective for stimulating yolk formation, yolk formation of oocytes can be seen from 49-62 days, whereas the control group of fish is up to 235 There is no egg yolk yet. (d) Water temperature is in the range of suitable water temperature. Water temperature increases the rate of gonadal development, and vice versa. (e) The ovaries of barramundi and barracudas are unable to mature although they can develop to stage IV in freshwater. Salinity stimulation is an important part of the development of gonads and barracudas. It is very important. The endocrine system in barramundi and barracuda is disordered in fresh water, and the histological structure of the pituitary also changes, or excessive prolactin inhibits the activity of gonadotropin-secreting cells (Nelly et al. 1970); or the absence of ovulation hormones And steroid hormones (Eckstein, 1975). The salinity of squid and barracuda brood pool water depends on the specific conditions of the sea and fresh water to be controlled according to local conditions. After the gonad develops to the third stage (barracudas in February, the squid will gradually increase the seawater after September), the salinity of the pool water will be increased to about 15 ( (barracuda) and 20 å‰ before spawning ( Carp), which is conducive to gonadal development, increase the number of flushes within one month prior to labor, once every 3-4 days. (II) Artificial oxytocin 1. Artificial oxytocin and barracuda are late in the morning and late in the season when our country mobilizes production. Barracuda production in Jiangsu is from the end of April to mid-May; Tianjin, Hebei and Jiangsu are similar; Liaoning area is about half a month later. Eel production in Jiangsu from December to January next year; earlier in Guangdong, Taiwan and Fujian. The time of spawning of ponds and barracudas cultured in ponds is about 10 days later than that of natural sea areas. The water temperature required for spawning is 204°C, and the high temperature is not conducive to artificial breeding. (1) The choice of mature broodstock The choice of broodstock is the key to ensuring the success of oxytocin production, especially for early oxytocin production. During the breeding season males generally mature naturally to sperm flow. Well-matured male fish gently press on both sides of the abdomen by hand and the semen will flow out. The semen of good quality turns into a thick milky white, which is dispersed evenly in water. If the semen is yellow, it is difficult to disperse immediately after entering the water, indicating that the semen is aging. If no semen can be squeezed, it indicates that the maturity is not enough or the cultivation is not ideal. The choice of female fish: Select broodstock for 1-2 days before broodstock, let broodstock excrete feces, so as not to cause the illusion of judgment. The appearance of mature females is more inflated, softer and more flexible in the abdomen, slightly more prominent in the anus, and ruddy around the excretory holes. The male's abdomen was small and flat, with no softness. In order to avoid the error of satiation and excessive accumulation of fat, a small amount of ovary can be directly taken out of the ovary for observation. Mature oocytes have diameters above 0.65 mm. The adhesion between the granules is loose, and they are separated by gentle stirring in water. At low magnification, the oocytes are milky white translucent, and fat droplets inside the cells are clearly visible and evenly distributed. If the eggs are black and opaque indicates that they are not mature, it is not appropriate to elicit labor; if the egg adhesions are flattened and even there are droplets of “oil†in the ovary, most of them are degenerating ovaries, and should not be used. The choice of broodstock sex ratio is better than 1:1.5-2. (2) Hormone and injection The hormones and drug types currently used for artificial puerperium and barracuda are commonly used: pituitary gland (GTH), luteinizing hormone-releasing hormone analogue (LRH-A) HCG, Synahorin, DOM and Vitamin E. Senacol is a product made up of a combination of 1/10 mammalian anterior gonadotropin and 9/10 placenta, and is generally based on the titer of the rabbit unit (RU). This is a hormone commonly used in fish breeding in Taiwan. The effective doses of various hormones per kilogram of scorpion and barracuda are as follows: GTH—15-25mg; LRH-A—200-300μg; HCG—3500-6000IU. The effect of mixed injection of GTH and LRH-A was better, and its dose was: GTH 10 mg + LRH-A 150 μg. The injections can be divided into two doses, with doses of 1/5-1/3 and 2/3 to 4/5 of the total dose. The interval between two injections is 15-24 hours, depending on the water temperature. When the water temperature is high, the interval can be shortened. The injection site is in the chest or dorsal fin. When mature, males may not be injected with hormones. Males with less mature semen may also be injected. The dose is half that of females and the last shot of females is injected together. In Taiwan, oysters are now used for the production of codfish, Cinnabarate and vitamin E. The total dose is 2.5-6 fish per pound of body weight, 10 to 60 RU of Cinnabarol and 0 to 300 mg of vitamin E. It is also generally divided into two injections at intervals of 24 hours. The use of pituitary and Cinacol has a significant effect. (3) When the broodstock that has been inoculated after oxytocin injection are stocked, such as natural spawning, they can be directly placed in specialized spawning ponds, cement ponds or large aquariums (over 0.5 cubic meters), and spawning containers with running water. Or inflate to prevent oxygen deficiency. Because of the irritable nature of the carp, the holding pool should be placed in a quiet place. The cage must be covered to prevent jumping. If artificial insemination is used, the broodstock can be placed in a polyethylene cage or a sieve basket. The cage can be placed in a spawning pond or a pond with clean water and raised at a time of 2-3 tails per square meter. In order to facilitate the male and female fish gonadal development, male and female should have their bins stocked. The cage is 50 cm above the water to prevent the brooders from jumping out. (4) The length of the effect time and the examination effect time are related to the water temperature and the maturity of the broodstock. High water temperature and good maturity have a short effect time, whereas they are long and vary greatly. The time from the last injection of a normal gonadal development to spawning was 20-30 hours, and the difference was 2-3 days or even longer. Check every 1-2 hours from the last injection for 15 hours, and watch for abdomen changes in the female. If the abdomen is significantly enlarged (the total volume of the ovary is significantly increased due to the "hydration" effect of the mature egg), indicating that the egg has reached the end of the egg production, it should be checked. If a small amount of free transparent egg can be extruded and can not be smoothly released, it can be over 1 - Check again after 2 hours. The oyster and barracuda eggs cannot stay in the ovary for too long after being discharged from the follicles. The time to maintain fertilization is only about 3 hours (17°C). After that, the barracuda becomes overly mature and gradually loses fertility. Therefore, it must be timely. Fertilization. (5) Artificial insemination Artificial insemination has two methods: “dry method†and “wet methodâ€. Regardless of the method, there is no difference in the fertilization rate and the key operations are rapid. Barracuda and barracuda are marine fish and their sperm activation and fertilization must be performed in a hypertonic environment. Salmon spermatozoa can be activated in water above 15 ;; barracuda sperm can only be fertilized in salty water above 5 。. The washability of the egg can be maintained for 1 hour during dry insemination, and within 5 minutes for the wet method. Barracuda spermatozoa can maintain their longest time at 18 ‰ and pH 8.2-9.0. After fertilization, the oocytes are screened to remove water, blood stains, and tissue mass. The volume of the whole egg is taken from the measuring cylinder and counted at 2,800 particles per ml before hatching. (6) Eggs of hatching quail and barracuda are spherical, transparent and buoyant, non-adhesive, and smooth. There is no pattern on the surface of the egg membrane of salmon, and barracuda is available. The diameter of the egg is 0.9-1.1 mm, and the width of the perispophysis after absorption is 0.015-0.020 mm. There is a big oil ball in the quail and barracuda eggs, which is the most obvious characteristic of mature eggs. The diameter of the squid eggs oil balls is 0.35-0.38 mm; the barracuda is larger, 0.43-0.52 mm. The proportion of quail and barracuda eggs varies with the broodstock environment. The eggs of salmon are sinking in the still water, especially the eggs that are not fertilized. It is difficult to recirculate the eggs to suspend the eggs, which will greatly improve the hatching rate. Barracuda broodstock is cultivated at 35.6 ‰ salinity, and its eggs are sunk at 20 ‰ salinity; for broodstock grown in water at about 10 ,, the eggs are buoyant at 15 ç› salinity; at 17 The eggs produced by the broiled broodstock raised in water of 20‰salinity are still semi-floating in water with a salinity of about 20‰. Oystercatchers and barracuda fertilized eggs can hatch at water temperatures of 12-24 °C. Carp hatching water temperature 11-24 °C, suitable for 18-20 °C, the optimum temperature is 22 °C, more than 25 °C above the death is usually more than 90%. The hatching water temperature of barracuda must not be lower than 12°C, and even less than 24°C. The suitable water temperature range is 15-20°C. Clam and barracuda hatch at 37-24°C for 37-52 hours. Incubation time is inversely proportional to water temperature. Oystercatchers, barracuda fertilized eggs are inflated and flow-type two kinds of hatching, mainly to make the water tumbling, keep the dissolved oxygen in water above 5mg/l, flow-type hatching with the four home fish hatching tank or hatching tank. Two kinds of hatching methods require the dissolved oxygen in water not to be less than 3mg/l, and the pH is between 7.8-8.5. The hatching density of the two hatching methods should be about 3 grains/ml. The salinity of carp hatching is 24-35 ‰, and the suitable salinity is 30-32 ‰. Generally, the requirement is more than 20 。. Barracuda hatching requires more than 7 inches, preferably 15 inches or more. After hatching fry, change the cylinder in time to remove sediment from the bottom of the tank and increase the survival rate of the fry. The fry were raised in the hatching container until the yolk sac disappeared, the larvae inflated, and the fry began to feed actively (the fifth day after hatching), and then moved into the nursery pond for cultivation. Second, the seed cultivation (a) The shape and feeding of barnyard mullet and barracuda seedlings The newly hatched larvae are about 2.5 mm in length and floating. The body is hanging upside down, tilted or the abdomen is facing the water. The body is transparent, with complete fin folds. Neither anal nor open. Mainly rely on the yolk in the yolk sac and oil in the oil ball as a nutrient. 4 to 5 days after hatching, the mouth has been opened, the upper and lower jaws are well developed, and the yolk sac and oil globules are consumed almost. The contraction of yolk sac is only 1/4 of the initial stage. The fry appears to swim and has begun to feed. At this time, Can be cultivated under the pond. The initial diet is mainly oyster eggs and larvae, rotifers, nauplii, but also egg yolk. As the larvae grow older, the digestive tract, body color, scales, and fins begin to develop well, activity and feeding capacity increase, and cracks increase. Individuals that can feed on the bait are getting larger. It is a dangerous period for eel and barracuda to start eating and feeding. The full-fledged fish fry of 20 millimeters began to change its habits, feeding zooplankton gradually to the bottom benthic dendrolimus, Chironomid larvae and other benthic organisms, and gradually appear in the feed sediment and organic debris, algae and so on. When the length of the fish reaches 60 mm, the food habit is basically the same as the adult fish. (2) The length of 2.5 millimeters of hatchlings and barracuda seedlings has just hatched. It can be cultivated in ponds or in concrete pools. For salmon and barracuda seedlings, special attention should be paid to changes in salinity, which must be consistent with the salinity of the hatching water in the initial stage. Dilution can be gradually carried out after 15 days, and fresh water can be used after 30 days. 1, pond cultivation area 1-5 preparation, water depth 1.0-1.2 meters. Before the stocking, the pond must be strictly disinfected with clear ponds to kill predators. Put 200-500 kilograms of organic fertilizer (such as pigs and cow dung) per acre one week prior to planting, 50-70 centimeters backwater. The fish fry can be used in the ponds of small zooplankton - ponds in submerged fish ponds, and 200 feet per litre of copepods can satisfy the feeding of fry. The density of barnyard mullet and barracuda seedlings is about 100,000 tails per mu. Generally, it is better to put seedlings in the wind at 3-4 pm. 1-2 days before seeding, “test the water†and observe whether the drug is invalid. When the fry are counted, they must carry the water to operate. Because the eel and barracuda are much weaker than the fish fry, they can easily die. In the initial stage of cultivation, fertilization was the main factor, and feeding was supplemented; feeding was the main method in the later period, supplemented by fertilization. Fish seedlings will be applied once every 3-5 days after Xiatang. Each time organic fertilizer 150-250 kg/mu will be applied, and appropriate amount of water will be added to improve the water quality and promote the growth of zooplankton. Soymilk is sprinkled twice a day. Soybeans use 1 kilogram of soybeans per acre and increase to 2.5 kilograms per day. After 25-30 days of cultivation, the length of mandarin fish and barracuda can reach 25-30 mm. After 2-3 times of pulling exercise, the survival rate can reach 70%. Pond cultivation should pay attention: the water temperature is too low below 15-17 °C survival rate is not high; open food less than easy to cause death; in addition to water quality deterioration, bacteria or parasites also easily affect the survival rate. The water temperature required by the pool is about 20°C, preferably over 20°C; the dissolved oxygen is 4-5mg/l; the water quality is good and the light is suitable. 2. Indoor cement pool cultivation This is a kind of high-density modern seedling raising technology, or it can use large-sized water tanks. At present, China has succeeded in breeding of barracudas. After 25 days cultivation per square metre, about 10,000 fry fishes with a total length of 25 mm can be cultivated, and the survival rate can reach 40-50%. Taiwan has also succeeded in raising trout. Indoor nursery is more suitable for carp, because the eel breeding season in the winter, and its breeding and raising water temperature requirements around 20 °C, indoor warming nursery by the natural impact of small, relatively constant water temperature. Its main facilities include: (1) The aeration system is mainly supplied by an air compressor or a Roots blower, aerated by aerated stones; (2) the heating system is heated by a boiler or electric heating device; (3) the water supply and drainage system; (4) the bait cultivation Pool; (5) other facilities, such as lighting. The main differences between indoor cement pond nursery and ponds are: (1) High stocking densities, which puts higher requirements on management, water quality, and bait matching; (2) Baits matching is the key, at different ages cultivated, according to larvae Differences in digestive system, morphology, mouth crack size, and motility provide different kinds and sizes of palatability baits, mainly live baits; (3) Water quality management guarantees dissolved oxygen at 6-8mg/l, control of ammonia nitrogen to harmful substances, early stage With water and a small amount of water for the main change, the latter is mainly to change the water, the highest when the amount of water up to 200%, when changing the water to pay attention to the temperature difference must be added by the preheated pool. At present, many shrimp rearing pools and crab breeding ponds in the north and south of China can be used for warming cultivation of barramundi and barracuda. Long-tailed and barracudas with a total length of 20-30 mm are already highly adaptable. They can live in brackish water or sea water, and they can also live in fresh water. Because the carp is not tolerant to low temperatures, the summer flower is usually listed in the fish and shrimp ponds for 250 grams in the same year (the south can be raised to the second year). Can also be monopolized, the current aquaculture area in the Guangdong coastal eel is very large, most of the seedlings that year were listed (mainly monoculture). Barracuda summer flowers can also be cultivated in the shrimp pond into 100-200 grams of large-size fish species, or special pool to develop 15 cm of 1 instar fish species, and then develop food fish the next year. The method of cultivating fish is the same as that of domestic fish, which can be mixed or monocultured. Third, the cultivation of food fish Traditional carp fish farming in the "fish", "Hong Kong raise" and other large-scale predominantly. Use low-lying land such as harbors, mudflats and sea otters to build dykes and dams, open trenches and build gates, block seawater, use natural tides and fishes, and use natural foods for breeding. This open type Due to variable stocking, extensive stocks in water bodies, numerous ferocious animals, uncertain food and inconvenient management, the output is very low, and there is no harvest in the face of natural disasters. Therefore, this farming method is gradually being replaced by small-scale intensive cultivation. . Barracudas and barracudas are omnivorous fish and are most suitable for polyculture with other fish. Can make full use of farmed water bodies and feeds, thereby comprehensively improving production and efficiency. (1) Polyculture and polyculture is the use of different food habits and habitat water layers to achieve the full potential of water bodies and the rational use of bait, which is an effective way to increase productivity. In saltwater ponds, oysters and barracudas can be mixed with tilapia, prawns, carps, and squid, etc. Taiwanese squid is mixed with milkfish and prawns. In freshwater fish ponds or in low salinity (below 5 ft), it can be mixed with some fish such as the family fish, tilapia, Polygonaceae, Polygonaceae, and Polygonaceae. 1. Freshwater or low-salt water polyculture can be carried out with barracuda or barracuda as the main fish culture, or home fish as the main fish. Here is an example: Polyculture of common carp and other fish on the two sides of the Pearl River in Guangdong is a common pattern, and most of them are polycultured with cockroaches, cockroaches, cockroaches (yellow fins, etc.) and cockroaches (aesculenta, barramundi). The model is shown in Table 9 (Note: quoted from Zhang Bangjie). Table 9 Pond polyculture based on catfish species Restocking species Specifications Stocking density Cultivation time Harvesting specifications Net production (tail/mu) (kg/tail) (kg) Carp 5-6 cm 250-300 1 0.5-0.61 125 Carp 0.25-0.5 kg / tail 100-150 2 251 125 Carp 0.5 kg / tail 25 2 250 30 Yellowfin fin 10-12 cm 150-200 1 250 20 Carp 5-6 cm 10-25 1 75 10 2 Diversification of seawater and water bodies Example 1: The East Sea Fisheries Research Institute from 1983 to 1986 at the Fengxian Marine Aquaculture Test Site, with the cultivating shrimps as the main polyculture carp, with an area of ​​2.32 mu and a water depth of 1.2-1.5 m. The results are shown in Table 9. Table 9 Test results of polyculture of prawns and squid in China Variety stocking and harvesting mantroll length body length of specification tail survival rate yield per mu (cm) (tail/kg) (%) (kg) (kg) China shrimp 45200 0.7-1.1 15 15570 34.4 259.5 112 Squid 990 4-5 2.1 720 72.7 85.7 36.9 Chinese shrimp 43700 0.7-0.8 9.2 13414 30.7 364.5 157 Squid 354 5-6.8 0.9 260 73.5 76.5 32.9 (Note: The first batch was the result of 1983, with screw Fish and other biological bait are the main products. The second batch was the 1984 result, fed with 30% compound feed and 70% biological feed.) Example 2: Polyculture of barracuda and shrimp. The test pool has an area of ​​3.3 mu and a water depth of 1.2-1.5 meters. Before stocking, fish ponds are used to clean the ponds and then filtered through 80 mesh sieves. The water's salinity is 18 inches. On July 1st, 20,000 shrimps with a body length of about 1 cm were stocked, with an average of 6060 tails per acre. On July 8th, a total of 201 pigtails with a total length of 10.3 cm were stocked. On July 15, a 1 year old barracuda with a total length of 12 cm and a small amount of a 2 year old barracuda with a weight of 150-200 g were also stocked, for a total of 390 fishes. A total of 591 species of barracudas were stocked in 3 age groups, averaging 179 per acre. From the 1st of July to the end of October 25th, a total of 1635 kg of feed was fed, including 500 kg of blue cockroach, 750 kg of fresh cockroach, 60 kg of shrimp, 50 kg of miscellaneous fish, 200 kg of pellet feed, and bean cake. 75 kg. During the whole period of feeding, fresh water was frequently flushed to improve the water quality, and fresh water was gradually added to reduce the salinity of the pool water to about 10‰ in the later period. The water quality is always “fat, live, and coolâ€, the dissolved oxygen is in good condition, and the floating phenomenon never occurs in fish and shrimp. The test results yielded a total of 300.3 kilograms of shrimp, most of which were 12-15 cm in size, with a survival rate of 71.8% and 210 kilograms of barracuda. The average length of barracuda in the year is 24.7 centimeters and the average weight is 141 grams. The average length of the 2 years old barracuda is 37.8 centimeters, the average weight is 390 grams, and the average age of the 3 years old barracuda is 510 grams. In addition, 17.5 kilograms of white shrimp and 4 kilograms of miscellaneous fish were harvested. The total yield of fish and shrimp was 161.4 kilograms, including 91 kilograms of shrimp and 63.7 kilograms of barracuda. In this experiment, the shrimp's specifications, survival rate, and yields all reached the level of monocultured shrimp at the same local stocking density. 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