Biological Characteristics and Artificial Breeding Techniques of Oreochromis aurea
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1. Morphological features: body side flat, back bulge, abdomen arc, no abdominal ridge, kiss blunt, prominent. The mouth is small, the mouth is not close to the front edge, no mouth to be, body height is 37.1%-44.3% of the body length (mostly 40%), 31.8%-36.2% of the head length, the tail handle length is tail handle height 0.66%-0.94%. The jaws of mature males did not enlarge, and the length of the mandibular jaw was 26.1% to 31.2% of the head length (average 28.8%). Dorsal fins hard spines 16, soft strips 28; anal fins hard spines 3, soft strips 9-10; caudal fins truncate, slightly rounded. Spine 29-30. The body is rounded and the cheeks have 3 rows of scales arranged horizontally, 5-7 in each row. Along the sideline gradation 31-35. The lateral line is divided into two segments, the upper line is 20-25, and the lower line is 11-15. The number of scales between the starting point of the dorsal fin and the upper line is 4-6. The number of scales between the starting point of the anal fins and the upper line is 12-14. The number of scales between pectoral fin base to pelvic fin base is 5-7. The juvenile grayish-gray has a golden luster and a deep vertical vertical band on the side of the body. The juvenile fish dorsal fin spiny stage has a large dark spot, which gradually disappears later and is replaced by a pale vertical stripe at the back of the fin; at the same time, The caudal edge of the caudal fin began to appear pale red, and the base of the caudal fin and the anal fin were also spotted one after the other; the side of the caudal fin was gradually turned into lavender with golden light. The fish is purple-gray, with golden brilliance. Head darker. The front cheekbone is blue and the iris of the eye is orange-red. There is a deep purple spot on the lid. The back is purple-purple, with 9-10 dark purple-grey vertical bands on the abdomen, with dark spots on the upper and middle parts of the band. The pigment in the center of the scale is deeper than the edge, and there are multiple columns of longitudinal dotted lines on the body side. The back and hip fins are purplish blue and purplish, and dorsal fins and anal fins are white to light yellow with blue spots. Pectoral fins yellowish and transparent. Pelvic fin darker than anal fin, caudal fin light gray, nearly transparent, speckled, spots early in the base near the caudal peduncle, silver-white, later with the age of irregular ribbon distribution, and gradually inlaid pale gold (A very small number of white or gold-like wavy vertical stripes are formed.) The upper edge of the dorsal fin and the end of the caudal fin are light red. Mature males are dark purple to purple-brown in the breeding season, with golden reflections, darker heads; dorsal fins and anal fins dark purple, the spots on which are pale blue; pelvic fins are dark blue; gold spots on the caudal fins shine. The pale red on the upper edge of the dorsal fin deepens and the end of the caudal fin is bright orange-red.
2. Living habits: Olivia tilapia is the strongest species of cold-tolerance in Tilapia and can still live normally at 10°C. It can survive in a wide temperature range of 12°C to 40°C with a growth temperature of 16°C. -36°C, the optimum growth temperature is 28°C-32°C. The fish has a lower critical temperature of 7°C-13°C, a lower lethal temperature of 3.95°C, and an upper lethal temperature of 40°C (tolerance of 3-4 hours).
The fish has a strong tolerance to water quality conditions and is suitable for aquaculture.
The fish has a wide adaptability to salinity. It can live in fresh water, but it can also live in brackish water or seawater. There are few diseases in seawater. In the 5 ‰ salty water, the cold resistance is much greater than in fresh water, and in salinity. The seawater ponds that fluctuate up and down 40 feet grew well, but the highest salinity recorded for breeding was only 18.9.
The fish has a strong ability to adapt to pH, but it grows better in neutral or slightly alkaline waters. The dissolved oxygen requirement is 3 mg/l or more. The critical value of asphyxiation for the 1st-instar fish at a water temperature of 26°C was 0.44 mg/l; for the 2nd-instar fish at a water temperature of 29.5°C, the critical value for asphyxiation was 0.81 mg/l.
3. Feeding: Olivia tilapia is an omnivorous fish with a wide range of food habits. It can eat a variety of algae, organic detritus and artificial feed. Juvenile foods, mainly rotifers, cladocera and copepods, but also a large number of smaller prey juvenile fish. Larger individual fish and adult specimens collected in the Nile Delta are mostly epiphytic algae; in Ababama's ponds, food is mainly fed feed and phytoplankton. It has also been found that ponds fed with artificial diets and fertilization are mainly composed of bottom layered substances such as benthic animals and organic debris. Few feeds are fed directly; however, artificial feeds and phytoplankton are also ingested when the stocking density is high and there is not enough food at the bottom of the pond.
4. Growth and development: It was determined that the stocking density was 1000 fish per 667 m2, artificial feeding was 4 months and the body length was 13.05 cm, the body weight was 89.75 g, and the average daily gain was 1.04-1.17 g. Under the conditions, the average daily gain of tilapia males was 86.03%-95.41%. Juveniles grow longer than their weight gains. Absolute growth in body length is fastest before July and gradually slows thereafter. The absolute increase in body weight was 9 months earlier, especially in August-September. There was no significant difference in body length and body weight between males and females of 1 year old Oreochromis niloticus. There was significant difference between the 2nd instar fish, male fish grew faster than female fish, and in the same batch of breeding stock, 2 winter male fish weight 443 - 622 grams, while females were only 52.43%-90.14% of the males.
Reproductive characteristics
When the Oriya tilapia was infertile, the male and female gonads matured in the second year. If the water temperature is appropriate, they breed and reproduce. The minimum age of reproduction is 1 winter, and the minimum body length for females is 12.6 cm and the body weight is 58 g. The male body has 10 body weights of 36 g. This shows that the spawning of the fish is not related to body length and body weight and is mainly related to age. In the case of dense cultivation, it grows slowly, and it can produce eggs even if it is small at a certain age.
The fish is a spawning type of fish. During different periods, the gonads of females were dissected. The eggs at different developmental stages can be seen. The fertility of individuals with different body lengths is very different. We use the IV ovary as the standard to dissect. Thirty-three fishes with a body length of 17-20 cm have 450-1764 eggs, a body length of 20.1-23 cm is 450-1890, a body length of 23.12-26 cm is 568-2142, and a body length of 26.1- 29 centimeters are 2028-2158 grains.
The fish can reproduce once every 30-50 days when the water temperature is 25°C-30°C, and the offspring sex ratio is 1:1. Sexual males have a higher mating color, body length, and weight than females in the breeding season. The ratio of body height to body length is also greater than that of females. The dorsal fins and anal fins are more distinct than females. The ratio of body height to full length was also greater for females than for females of the same color, body length and body weight. The dorsal fins and anal fins were longer than females (secondary sex). The minimum water temperature for breeding is 20°C-22°C. Guangzhou generally begins to breed from the spring and enters the peak period in early summer. After the summer temperature exceeds 30°C, the reproduction is reduced. During the breeding season, mature males set up a 0.7-1 meter area and dug a recessed spawning foe with mouth and fins. The male guards the territory and spawning nests, and occasionally swims to the fishes passing by from nearby, until he leads a mature female into the nest. After fertilization in the nest, the females leave the entrance of the fertilized egg. The male fish then went on to find other mature females and continue breeding activities. The incubation time of fertilized eggs depends on the temperature and it takes 13-14 days at 25°C-27°C. The juveniles are still intensively close to the head of the mother fish for about 3 days, and will be re-homed to the entrance in case of danger. This kind of parent-child relationship will end in 5 days. The females then enter a new breeding cycle.
Breeding technology
1. Fry reproduction: Choose bred fish that are robust, non-invasive, and have the typical characteristics of the fish. Each 667 square meters stocks 250-500 g/tail female fish with 600-750 tails, or 1,000 females with 150-200 g/tail. Feed artificial feed 1-2 times a day. Common feeds include bean cakes, rapeseed cakes, peanut cakes, rice bran, bran, and corn flour. At present, artificial propagation of tilapia has not been successful and can only depend on the natural reproduction of tilapia to obtain seed. When the water temperature is stable above 18°C, the female and male fish are placed into the spawning pond at a ratio of 3:1. The fish began nesting at a water temperature of 20°C and prepared for fertility. Spawning temperatures were above 25°C. Fertilized eggs hatch at a water temperature of 26°C to 30°C and leave the membrane for about 5 days. After 15 days, they leave their mother's mouth to live on their own.
Seedlings are usually taken in the morning or early evening to see more time.
2. Fish species cultivation: There is no special requirement for fish breeding ponds. Ponds, concrete pools, or cages can be used. The area can be large or small, and the water depth is preferably about 1.5 meters. It has good water source, convenient drainage and drainage, suitable water quality, and rich feedstuffs. If cages are used for cultivation, closed floating cages are usually used. The height is generally 1.5-2 meters and the volume is 10-30 cubic meters. The water depth of the set water area is 3-5 meters, which should be set at the leeward position in the waters.
When ponds are used for cultivation, 10 days before transplanting, dry ponds and lime-cleared ponds are used. After 3-4 days, the water is discharged 70-80 cm deep, and 4-5 days before planting, 400-500 kg of manure per 667 square meters of fertilization, or green manure is used. 400 kg. When laying the seedlings, the fry that has lived for one week after independence is picked from the broodstock spawning pool. Fishing seedlings are generally selected when the fish clusters swim in the morning or early evening. Stocking densities range from 30,000 to 50,000/667 square meters, with a maximum of 80,000 tails. Soymilk is used as an open feed, 1.5-2 kg of soybeans per 667 square meters. After the fry grows to more than 2 cm, it should be fed with a cake or a rapeseed cake. When the transparency of the water body is less than 25 centimeters, new water should be added, about 15 centimeters at a time, and water should be added 3-5 times throughout the incubation period. After 30 days or so, the pond can be dredged to 5 cm or more. Change the stocking density to 7000/667 square meters and cultivate to 100 grams. Feeding artificial compound feed, 3 times a day, the daily amount of feed is 3% -4% of the fish's body weight.
3. Commercial fish rearing: The pond area is 3333-13334 square meters (5-20 mu), the water depth is 1-3 meters, the stocking density is 500-700 tails/667 square meters, and the feeding amount is 3%-5% of the fish weight, generally Every day at 9 a.m. and at 2 a.m., each feeding is performed once. The feed type is the same as that of the broodstock. The management must pay attention to fertilization, and the water transparency is 25-30 cm.
The stocking density of cages varies with the environment of the water body, ranging from 30 to 80 tails per cubic meter. Feeding is done 2-4 times a day, and the daily feeding amount varies by 3% to 10% of the fish's body weight. Day-to-day management is mainly to prevent escape. Wash the cage once every 5-7 days.
Disease and Prevention
Tilapia fishes generally have strong disease resistance, but they also have the following diseases when stocking densities are relatively high. The fish is more sensitive to drugs and should generally use drugs with reliable and mild effects. The dosage of drugs is lower than that of other fish.
1. Bacterial diseases
(1) The incidence of gill disease in spring and summer is high. The pathogen was columnar fibrobacterial infection. Control methods: General Quanchiposa disinfectant (chlorine), while oral antibiotics, such as furazolidone, norfloxacin and ciprofloxacin, etc., have a good effect, continuous feeding for 3-5 days.
(2) The incidence of enteritis is high in spring and summer. Control methods: Furazolidone or allicin + 2% sodium chloride is usually fed continuously for 3-5 days, or 0.1 g of sulfadiazine and 0.3 g/kg of fish fed with trimethoprim are cured after 3 days; then Quanchipid is used to disinfect the drug. , improve the water environment.
2. parasitic disease
(1) The incidence of echinococcosis is usually early winter and early spring. The pathogen is a parasite infection of many small melons. Control method: 0.2 kg of lime per cubic meter of water, splashed in Quanchipue; soaked with 2 g of Hg(II) solution for 2 hours, or 3 mg/L of methylene blue for Quanchiposa, and spilled once every 3-4 days. 3 times.
(2) It refers to the incidence of cysticerosis in spring. The pathogen is parasitic infection of the worm. Control methods: 1 meter deep fish ponds use 150 kg of clear lime per 667 square meters, fish species before sowing are soaked with 20 mg/elevated potassium manganate solution for 15-30 minutes, or use 0.2-0.3 mg/L crystals Insect Quanchiposa.
(3) The third generation of helminthosis generally occurs in spring, and the pathogen is the third generation parasitic infection. Control methods: Use 0.2-0.3 mg/l crystal trichlorfon Quanchiposa.
In addition, there are non-pathogenic diseases, such as frostbite, nutritional diseases, such as malnutrition, which usually occur in the wintering period.
Pure breeding and utilization of heterosis
Because tilapia males grow 40% to 50% faster than females, if they can produce all-male species, pond production can be significantly increased without any additional investment. This is an equally tempting task for super rice cultivation. At present, the method of obtaining all-male offspring is the induction of chemical drugs (such as male hormones). This technology has an impact on the safety of human food; the second is the use of male and female development techniques to produce super-male fish, but it is technically difficult. The third is the use of different gender mechanisms of different species of tilapia, through hybridization, to produce all male offspring. For example, the sex chromosome of Oreochromis aurea is composed of homogametes (zz), and the sex chromosomes of females of Nile tilapia are homogametes (XX), and the sex of the two hybrids is theoretically 100% ( ZX) Male. This technology is relatively simple and easy for producers to master, but the key point is the germplasm purity of the two varieties; the males of the non-pure hybrids only have a male rate of only about 80%, and due to the breeding of females in the hybrid offspring, And it affects the yield of the pond. Therefore, pure breeding has become the key to the utilization of heterosis in the two varieties. Pure breeding is the key to selecting the best from generation to generation and maintaining the advantages of using hybrids. Pure breeding is to select the best from generation to generation, keeping the male rate of hybrids stable at 95%. Oni hybrids grew rapidly. In 1997, they were kept for 120 days in the ponds in Jingshui, Guangdong, accounting for 30% of individuals weighing 0.75 kg or more, 50% of those weighing more than 0.6 kg, and 20% of those weighing 0.5 kg or more. On average, the output was 682.8 kg per 667 square meters, of which Otani fish accounted for 89% and in 1998 it accounted for 91%.