Morphological characteristics: flat body, medium head size, mouth in the terminal position; Eyes are the same size, slightly higher than the head. The mandible of mature male fish is not enlarged, and the length of mandible is 29-37% of the head length. The scale is large and round, and the lateral line is divided into two sections. The upper line has a scale of 18-24, and the lower line has a scale of 12-22. The number of scales along the side line is 30-35, usually 32-33. The dorsal fin is developed, starting from the rear edge of gill cover and ending at the front end of caudal stalk, with hard spines 16- 17 and soft strips12-13; The end of the gluteal fin exceeds the caudal stalk, and there are 3 hard spines and 9- 1 1 soft strips. The pectoral fin is long, reaching or exceeding the end of the ventral fin, with no ridge and soft strip14-15; Chest position of ventral fin, hard thorn 1, soft strip 15. The tail fin is blunt and rounded at the end. The tail fin of young fish is flat, and that of adult fish is fan-shaped. Body color is yellowish brown to yellowish brown, from back to abdomen, from deep to light; Diphtheria with white chest. Adult fish males are red; There are 9 black belts perpendicular to the body axis on both sides of the body, including 7 under the dorsal fin and 2 on the caudal stalk; The edge of dorsal fin is black, and there are regular black stripes on dorsal fin and gluteal fin; Tail fin and pectoral fin have red edges, and salted fish males are particularly bright; The female fish is dark in color, dark brown when hatching, with obvious body stripes and some irregular black stripes on her head.
Living Habit Nile tilapia is a tropical fish, the suitable temperature range is 16-38℃, the optimum water temperature is 24-32℃, and it grows fastest at 30℃. The upper limit of lethal temperature is 42℃ and the lower limit is 10℃. 14- 15℃ loss of appetite. 10℃ without feeding.
Nile tilapia has a strong tolerance to hypoxia. When the water temperature is 22-25, the dissolved oxygen (DO) is 0.7 mg/L, and only the faint floating head is exposed, but it can still be eaten. When the dissolved oxygen is 2.24 mg/L, the food intake is vigorous. In order to maintain normal growth, dissolved oxygen in water must be kept above 3 mg/L and below 0. 1 mg/L to suffocate. The pH value is between 7.5 and 8.5 below ammonia nitrogen1mg/l. Carbon dioxide is less than 50 mg/L.
Nile tilapia is a euryhaline fish, which can adapt to a wide range of salinity changes and can be directly removed from fresh water with salinity of 15‰. In the sea, and vice versa. If the salinity is gradually increased from the lower salinity (1.5 ‰), after short-term domestication, it can grow normally in seawater with salinity of 30‰ and still survive at salinity of 40‰.
Nile tilapia generally lives at the bottom of the water. It swims to the upper middle layer with the change of water temperature in the morning, near the water surface at noon, to the lower middle layer at night, and rests at the bottom at night and dawn. Young fish like to swim in groups. When an adult fish encounters an enemy or trawl, it jumps first and then dives into the soft mud at the bottom, with its mouth sticking out of the mud.
In the larval stage, almost all of them feed on zooplankton-rotifer eggs, copepods, nauplii and small cladocera, and gradually become omnivorous with the growth of individuals. In natural water, the kind of food depends entirely on the kind and quantity of natural bait. Usually, phytoplankton and zooplankton are the main food, but also benthos, aquatic insects and its larvae, even small fish and shrimp, and sometimes aquatic plants. In the adult stage, phytoplankton are the main food, among which cyanobacteria account for 70%. Some algae, such as silver carp and bighead carp, which are difficult to digest and utilize, can be well digested and utilized. The assimilation efficiency of the fish to Chlamydomonas, Microcystis, Anabaena, Nitzschia and Chlorella is 75%, 70%, 75%, 79% and 49% respectively. Under the condition of artificial feeding, in addition to the above natural bait, a large number of commercial feeds, such as bran, oil cake, bean dregs, distiller's grains, artificial compound bait, etc., are also ingested. Using various commercial feeds to feed the fish can achieve remarkable results, and the combination of feeding and fertilization can also be used in production, which can achieve better economic benefits.
Distribution waters Nile tilapia is native to Lake Tanganyika in Jordan, Africa, and distributed in rivers along the coast of Africa and Israel. Mainly distributed in Senegal water system, Nile water system and lakes in Egypt; Also distributed in the volta river river system and the Niger river system. Widely introduced by other countries and regions, it is a high-quality aquaculture variety recommended by the United Nations.
Country of origin: Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Democratic Republic of Congo, C? te d 'Ivoire, Egypt, Ethiopia, Gambia, Ghana, Guinea, Israel, Kenya, Mali, Mauritania, Nigeria, Rwanda, Senegal, South Sudan, Sudan and United Republic of Tanzania.
Introduction: Bangladesh, Belgium, Bolivia (Plurinational State of), Botswana, Brazil, Brunei Darussalam, Cambodia, China, Colombia, Goma, Congo, Costa Rica, Cuba, Cyprus, Czech Republic, Dominican Republic, Ecuador (Galapagos), El Salvador, Eritrea, Fiji, Gabon and Grenada. Italy, Jamaica, Japan, Kiribati, Korea, Lao People's Democratic Republic, Madagascar, Malaysia, Mauritius, Mexico, Myanmar, Nepal, Nicaragua, Pakistan, Panama, Peru, Philippines, Puerto Rico, reunion island, Saint Lucia, Saint Vincent and the Grenadines, Sao Tome and Principe, Saudi Arabia, Singapore, Slovakia, South Africa and Singapore.
The first sexual maturity of Nile tilapia is 4-6 months. High temperature, good nutritional conditions, fast growth and early maturity, otherwise it will mature late. The first sexual maturity150-200g, the male fish matured earlier and the individual was larger. After overwintering, due to the long overwintering period, the mature age of fish species has generally reached or exceeded 6 months, and the growth is slow or even stopped. Therefore, individuals weighing only about 50 grams can mature and lay eggs when the water temperature is suitable and the feeding conditions are improved. It can be seen that the development and maturity of gonads are not only related to the growth of individuals, but also play a decisive role in age.
The male-female ratio of young fish is 1: 1, salted fish is 1.2: 1, and fish over 28 cm is 0.47: 1. In Guangdong. In Fujian, they lay eggs 3-4 times in 1 year with an interval of 30-40 days each time. In the Yangtze River basin,/kloc-0 spawns 2-3 times a year, with an interval of 30-50 days each time. The second spawning is more than the first. The fecundity of Nile tilapia varies with individual size. The individual fertility of body weight100g is 800- 1000. Individuals weighing 200 grams can conceive 1200- 1500 eggs, up to more than 2000 eggs.
The reproduction of Nile tilapia is not limited by other ecological conditions except temperature. When the water temperature reaches 22-32℃, it can lay eggs all the year round. The water temperature is above 38 or below 20, and few or no eggs are laid. The spawning cycle is about 30 days, but there are great differences among individuals. The shortest spawning cycle is only about 15 days. In an earthen fish pond, before laying eggs, males usually dig holes to build nests, but fish nests are not necessary for laying eggs. In cement ponds or aquariums, they can lay eggs and fertilize normally without nesting environment. The reproductive behavior of this kind of fish is very special. The male fish of * * * is particularly bright in color and is busy digging holes to build nests. When there are mature females in the fish, he will tease and eventually form a partner. When laying eggs, it is next to the female fish. When the female lays eggs 1 time and turns back to contain eggs, the male ejaculates. Sperm eggs are put into the mouth by the female fish, and this process must be repeated for more than 5-6 times before laying eggs. The fertilized eggs hatch in the female fish's mouth. When the water temperature is 25-30℃, the fry can hatch for about 100 hour. The newly hatched fry are tender and weak, and continue to hatch in the female's mouth. After about 5-6 days, the fluidity of the fry increased, and the female fish spit out the fry, but when she gave an alarm, the female fish would put the fry in her mouth again. After hatching 10 day, the mother fish can safely leave and live an independent life.
Breeding technology The breeding of fry selects pure fish with strong physique, no damage and typical characteristics as the parent fish. 250g for females (minimum not less than 150g) and 400g for males (minimum not less than 250g). Or 2-year-old fish with 350-400g female fish and 2-year-old fish with 750g male fish. Choose a fish pond with an area of about l333 square meters (2 mu) and a water depth of 0.8- 1 m. After the pond is cleaned and disinfected, 300-500 kilograms of base fertilizer is applied every 667 square meters. When a large number of plankton appear in the pond water and the water temperature is stable above 65438 06℃, the parent fish can be released, and the selected parent fish can be released according to the ratio of (4-5): 60.
The fish pond for cultivating fingerlings has an area of 1333-2000m2 (2-3mu), a water depth of 1m and a flat bottom. Plankton has been cultivated, and 80,000-65,438+10,000 fish fry are stocked every 667 square meters. The fry are fished out from the spawning pond of the parent fish with a net or a dragnet, and the fry size is 2-4cm; Pulling the net too early, the fry are tender and weak, causing heavy casualties; It was too late to pull the net, and the fish was scared to dive to the bottom of the pool and it was not easy to catch it. 15 days later, the body length can reach 3-4 cm, and then the fry of this specification are put into the fish pond for secondary cultivation. When it grows to 6-7 cm, it will be put into a fish pond to develop commercial fish. At the stage of 0.5- 1.5 cm, soybean milk and soybean milk powder should be fed; Feed 1.5-2 kg of rice bran per 10,000 fry with a body length of 2-3 cm; Feed rice bran 65,438+0-65,438+0.5 kg per 1,000 tails per day if the body length is 3-5 cm. At this time, you can also feed a proper amount of turnip or duckweed or crushed and sieved granular bait powder. After 5 cm, feed 1- 1.5 mm pellet bait. Pay attention to killing scorpion, safflower, centipede and pine algae in time. In addition, fresh water must be injected regularly.
Adult tilapia can be cultured in seawater and fresh water ponds, cages, factory warm water and rice fields.
Pond culture: the pond area is not more than 3,333-6,667 square meters (5- 10 mu), the water depth is 1.5-2 meters, the bottom of the pond is flat, and the silt is not more than 20 cm. Convenient injection and drainage, and the water quality meets the fishery water quality standards. It can also be cultivated in waste pits, depressions, small ponds and ditches. It can be polyculture or monoculture, and polyculture is adopted at present. Polyculture fish usually include grass carp, herring, silver carp, bighead carp, carp, crucian carp, bream and so on. Every 667 square meters, 200 summer Nile tilapia and 400-600 other fish are released, and the yield can be increased without increasing fertilization and feeding, 15-. If fertilization and feeding are properly increased, the yield can be increased by more than 50%. Good results can also be obtained by single culture. 2,000-4,000 summer flower fingerlings are put into every 667 square meters, and the average weight is 150-300 grams, and the yield is 300-350 kilograms per 667 square meters. By increasing fertilization and feeding, the yield per 667 square meters can reach more than 800 kilograms. If spring seedlings are stocked, the yield can be increased by more than 15-20%, and the specifications of commercial fish can be improved by more than 1 times. Raising this kind of fish in the pond is easier to achieve high yield than the four big fish, and the high yield can reach more than 500 kg under the condition of sufficient fertilizer bait. Cage culture: This kind of fish can be cultured in cages in rivers, lakes, reservoirs, bays, estuaries and other water bodies. The location of the cage should be in Kuwan, Huhan or Bay where the leeward is sunny, the water body is slightly flowing, the water quality is fresh and the water depth is 5- 10 meters. Don't put the cage at the entrance of rapids or floods. The bottom of the pool is at least 2 meters away from the bottom, the water transparency is 1.2-2 meters, and the dissolved oxygen is 5-8 mg/L. The arrangement of cages is at right angles to the direction of water flow. The cage row spacing is 3m, and the cage spacing is 2.5m Every 8- 10 cage has 1 units, and each unit is 30m apart. The total area of cages shall not exceed 3% of the total water area to prevent eutrophication of water bodies. Each row of cages must be fixed by piling. The cage size is generally 10-30 cubic meters, and the cage height is 2 meters. The stocking amount of natural bait is 200 pieces/m3; Artificial feeding, 1000 /m3. Fish below 50g are fed at 5% of body weight, fish above 50- 100g are fed at 4% of body weight, and fish above 100g are fed at 3% of body weight. Adjust every 2 weeks 1 time. Check whether the cage is damaged and the frame is loose every day. Clean the cage regularly. At the end of 1980s, the output of tilapia cultured in cages was only 25-50kg/m3, and that of Shanghai Fisheries Research Institute reached 97kg/m3. The output of cage culture can reach about 150kg/m3, and the output of small-volume cage culture in Shandong Province is 180-220kg/m3, with the specification of 500g/ tail. It broadens the ways of reservoir culture. Mariculture: Drainage channels in bays, salt ponds and beaches can be used to raise this kind of fish. Fish ponds on the beach should be 6667- 13333 square meters (10-20 mu), and the water depth should be above 1 meter. The fish grows fastest in 15‰ seawater, and 100% survives. Transferring from fresh water to seawater or from seawater to fresh water must be domesticated. Stop feeding 2-3 days before domestication. If it is in a fertilizer pond, it should be moved to a clear water pond for 2-3 days and then domesticated. Domestication began with seawater with salinity of 5- 10‰, and moved into seawater with salinity of 15‰ ten days later. Growing up in high salinity seawater. Increase the salinity by 3-5‰ every L day until it is fully adapted to seawater. Feeding is not allowed during domestication, especially in the early stage, to avoid death caused by dehydration and indigestion of internal organs. Can be mixed with shrimp, mullet and barracuda. Paddy field feeding: under the condition of not increasing bar and feeding, the yield per 667 square meters is about 25 kilograms, which can increase rice yield. This kind of fish plays a more prominent role in the symbiosis of fish and rice than other fish. Raising tilapia in paddy field is of great significance to solve the problem of people eating fish in hilly and mountainous areas and increase economic income. Factory running water feeding: anything that can form a certain flow and is suitable for fish farming can be used as running water for fish farming, but the most ideal and economical way is to use factory warm drainage to raise fish without additional power equipment, which can realize automatic exchange of pool water and can be produced all year round, greatly improving the utilization rate of equipment. This fish culture mainly relies on artificial compound feed, with crude protein of about 30%, daily feeding rate of 5-7% and output of 25-50k g/(m3/ month). Overwintering tilapia is a work with high technical content, great difficulty and high cost. It is best to use waste hot water from factories, geothermal water or groundwater for wintering, which is both economical and effective. Where the water temperature is lower than 65438 06℃ in winter, heat preservation measures must be taken to protect species from overwintering. Healthy pure fish are selected for wintering, and the water temperature is kept at 18-20℃ during wintering. In this temperature range, fish can eat normally, maintain good water quality and sufficient oxygen, and increase their wintering ability. In general, species do not need to survive in winter, but it cannot be lower than 16℃. If the temperature is lower than this, the fish's physique will be reduced and it is easy to get sick. Fish should be soaked in 10 mg/l bleaching powder or 2-3% salt solution for 5 minutes before overwintering. The wintering pond also needs disinfection. In a fish pond with a water depth of 1 m, 30-40 parent fish of 200-250g and 300-400 fish of 4-5cm are put into each cubic meter of water. Feed at 0.5-3%, keep dissolved oxygen above 2 mg/L ... Remove feces and residual bait regularly and replace them with fresh water.
Prevention and treatment of hemorrhagic septicemia: It is caused by Aeromonas hydrophila infection when the breeding density is high, the water quality is deteriorating and some essential vitamins are lacking in feed. It can also be caused by extreme microorganisms, β -hemolytic streptococcus and Edwardsiella tarda infection. The more serious the illness, the more difficult it is to treat. Prevention and control methods: reasonable breeding density, good water quality, feeding full-price compound feed, adding oxytetracycline or sulfanilamide to eliminate sick fish. Canker: It is easy to occur in high-density feeding water. Caused by Aeromonas hydrophila infection. Control method: Spraying 0. 1-0.2 mg/L furazolidone in the whole pond, feeding furazolidone bait, and injecting 75,000 units of streptomycin into the back of untreated parent fish, with the curative effect of 100%. Cucumber disease: the main common disease in winter. When the water temperature is 15-25℃, many cucurbits invade the skin and gills, forming white punctate vesicles, increasing mucus on the body surface and gills, dark red gills, slow movement of fish, difficulty in breathing and floating on the water. Prevention and control methods: Before overwintering, the solution made of 200mg/L quicklime is spread all over the pool to kill melon insects. After the onset, 0. 1-0. 15 mg/L mercurous nitrate was sprinkled into the water once a day for 3 days. Trichinellosis: Trichinella spiralis invades the skin and gills, causing a lot of mucus secretion, forming a gray-white film on the body surface, with red and white gills floating all day. When the water temperature is 15-20℃, it will die within 3-5 days, and a large number of fish will die. Prevention and control methods: Before fish enter the wintering pond, soak them in 8mg/L copper sulfate solution 15-30 minutes. After the onset, the mixture of copper sulfate and ferrous sulfate (5:2) was sprinkled all over the pool water to make the concentration of the pool water reach 0.7 mg/L; Or soak the sick fish in 2% salt water or 0.4-0.5% formalin for 5 minutes. Rotiferosis: caused by rotifers parasitic on the body surface and gills. It is most likely to happen in the case of small area, shallow water and high stocking density. The sick fish swam alone, floating on the water and moving slowly. Precautionary measures: thoroughly clean the pond with quicklime. Use mixed compost to feed fry and fingerlings, not big grass or fertilizer. Rotifers were killed with 0.7 mg/L copper sulfate or a mixture of copper sulfate and ferrous sulfate (5:2). Fish louse disease: parasitic body surface caused by large number of fish louses. Control method: clean the pond with quicklime, and spray 90 pieces of crystal trichlorfon in the whole pond at the dosage of 0.25-0.5 mg/L. Lepidopteran anchovies: caused by the invasion of Lepidopteran anchovies. Its optimum breeding temperature is 20-25℃, it can breed at 65438 02-33℃, it can overwinter on fish, and its longest life span is 5-7 months. Prevention and control methods: the same fish lice disease. Water mold: Water mold invades the skin from the wound of injured fish, breeds into floc, and can spread to the whole body in severe cases. The sick fish is restless and swims slowly. To avoid this disease, we must first avoid hurting fish when pulling nets, transporting and operating; After the onset, raise the water temperature to above 20℃ or spray methylene blue solution with the concentration of 0. 1 mg/L in the whole pool once a day for 2 days. You can also soak in 3-4‰ salt solution for 5 minutes. Squamous disease: caused by bacteria, which occurs all the year round. Scales stand upright, with rotten fins, hyperemia at the root of fins, abdominal swelling and other symptoms. Prevention and control methods: avoid hurting fish when pulling nets, transporting and stocking; Soak the sick fish in the mixed solution of 2% salt and 3% baking soda 10 minute. Bubble disease and eyeball white candle disease: Nile tilapia that overwinters directly with hot spring water or groundwater is prone to nitrogen bubble disease. The water in the wintering pond is old, and there is too much ammonia in the water, so the fish eyes are prone to white turbidity. Prevention and control methods: the water in the wintering pond must be fully aerated in advance, and the recycling of the original pond water should be stopped, and new water should be injected, or ammonia nitrogen should be removed by filtration, and ozone should be sent to the water for forced oxidation; Feed fresh feed. Protection status and protection level: included in the IUCN Red List of Endangered Species (IUCN 2065438+VER 3.1in 2008)-No Danger (LC).
The main value of Nile tilapia is the largest variety of tilapia, and it has few bone spurs, tender and elastic meat, delicious taste, and its flavor can be comparable to that of sea snapper and flounder. Every100g of meat contains 20.5g of protein, 6.93g of fat, calcium, phosphorus, iron, vitamins, etc., and has high nutritional value. Tilapia muscle is rich in protein, complete in amino acids and rich in essential amino acids. The proportion of essential amino acids is basically in line with FAO/ WHO standards, and it is rich in delicious amino acids such as glutamic acid, glycine, alanine and aspartic acid. It is a comprehensive and high-quality protein source and an ideal animal food for human beings.
The main species Nile tilapia is the offspring of a cross between a pure male Nile tilapia and a pure female Nile tilapia. The male chromosome of the offspring is XZ type, which is due to the fact that the male of Nile tilapia is ZZ homozygous and the female is XX homozygous, resulting in XZ heterozygosity of hybrid gametes. The weight gain of hybrid male is 1 1.32-24.45% higher than that of female parent Nile tilapia, 17.76-72.7% higher than that of male parent Oreochromis aurea and 16.97-40.8% higher than that of Fushou fish. The yield of the population is higher than that of the female parent 18.72-37.05%, that of the male parent/0.54-85.39%, and that of Shoufu fish/Shoufu fish/Shoufu fish/Shoufu fish/Shoufu fish/Shoufu fish.
Longevity Fish Longevity Fish is the hybrid offspring of female Mozambican Roffi and male Nile Roffi, which has heterosis. Its growth rate is 96.5% faster than mosaic tilapia, 56.7% faster than Nile tilapia and 36.5% faster than its reverse hybridization. The meat content, protein content and fat content of the first generation of Fushou fish were higher than those of Nile tilapia. The second generation of Fushou fish still has heterosis, but it is slightly inferior to the first generation of Fushou fish, so the breeding of two parents should be strengthened.
YY type super male tilapia Super male tilapia is a sex chromosome YY type super male fish produced by hybridization between Mosbick tilapia and Nile tilapia, and its growth rate is 26-58% faster than that of Nile tilapia.
Red tilapia Red tilapia is a hybrid of red mutant of Mo subic tilapia and Nile tilapia with normal body color, which is a new variety formed by long-term directional cultivation.