1. Biological characteristics of tilapia Tilapia is native to Africa. It is also known as an African trout in the shape of a catfish. 1.1 Tilapia is a tropical fish with a suitable temperature of 20°C-35°C, an optimum temperature of 25°C-32°C, and a slow growth below 20°C. It stops feeding at temperatures below 16°C and begins to die at the end of 14°C. 1.2 Tilapia is resistant to hypoxia and can still survive under 1.5 mg/L of dissolved oxygen. It starts to float at 1.0-1.2 mg/L and begins to die at 0.3 mg/L, which is much lower than that of the four major fishes. demand. 1.3 The tilapia has a wide range of food habits. Insects, phytoplankton, zooplankton, epiphytic algae, and organic detritus in the water can all be used, and cyanobacteria that cannot be used by other fish can be used. 2. Species of tilapia At present, domestically cultivated tilapia are Nile tilapia, Oreochromis aurea, and some hybrids such as Jifu fish, Fushou fish, and rainbow trout. 2.1 The main characteristics of Nile tilapia: Brownish yellow under normal conditions, with 9 black stripes on the side of the body, 7 under the dorsal fin, 2 tail caudal stalks, and more than vertical black stripes on the caudal fin. 2.2 The main characteristics of Oreochromis odoratus: there is an ancient bronze patch behind the lid, with dark blue pelvic and anal fins, white spots on the dorsal fin, reddish rims of the fins, truncated trailing edge of the caudal fin, pale orange with yellow, fins. It was covered with neat light yellow spots. 2.3 Longevity fish: Hybrids of Nile tilapia (female) and Mozambique tilapia (male) have an all male rate of 90%, which is characteristic of Nile fish, and there is no obvious advantage in growth rate. 2.4 Gyrofish, also known as Onyx: a hybrid of Nile tilapia (female) and Oriya tilapia (male), with large individuals, fast growth, high male rate, high yield, and strong cold tolerance (The extreme temperature of 8°C) is characterized by the characteristics of the Nile fish, and its second generation lost its breeding significance due to impure broodstock. 2.5 The rainbow trout (also known as red Luofei): is a variant of the self-variation of Mozambican tilapia cross hybrid with Nile tilapia, its color traits are unstable, offspring will produce separation, red Luofei body surface was Red or red, white and black. Good breeds, individuals with bright colors, golden patches on the body surface, fluorescent spots on the dorsal caudal fins, white peritoneum, and fast growth rate are excellent breeding species. 3. Tilapia fingerlings Because tilapia is a tropical fish, its annual growth cycle is short. Therefore, choosing different seedlings according to different conditions is the key to culture. There are three species of tilapia based on their source and culture. 3.1 The seed produced in the fall is overwintering in the greenhouse and put into seedlings in the second year. The rapid growth of this seedling and strong disease resistance are particularly suitable for fishing pond stocking. The disadvantage is that if it is not an all-male seed, it will easily produce a large number of seedlings in the pool. 3.2 Early propagation seedlings, that is, the use of plant waste heat or geothermal breeding in early spring, the individual growth of this fry is fast, but the resistance is not as good as the former, the advantage is that in the breeding process basically no seedlings or only a small amount produce. 3.3 Small seedlings propagated in early summer, this seedling population has a high multiple of weight gain. After a breeding cycle, the product specifications cannot be reached. It is necessary to continue cultivation in the greenhouse and develop commercial fish before and after the Spring Festival. In the breeding, the first two seedlings are generally selected and there is an after-winter condition available for use. 4. Tilapia populations control tilapia because of its early maturation and over-breeding, leading to impediments to colony growth and often failing to meet the required commodity specifications within the intended culture period. 4.1 Population control by genetic means China now mainly promotes the offspring of the hybrids of Nile tilapia with the male of the Oreochromis auratus, which is characterized by a high male rate and effective control of reproduction. Force, combined with its hybrid advantages, has the characteristics of fast growth, low temperature resistance, high population output, and easy catching. 4.2 Non-genetic means to control tilapia populations 4.2.1 Use of androgens for induction of functional male fish To avoid the breeding of tilapia, oral male hormones are used to treat tilapia fry and induce Its genetic females are converted into functional males. Tilapia fry treated with drugs, size is the key to the success of inducible conversion, the fry must be applied prior to sexual differentiation (including sex differentiation), if the fry after sexual differentiation is invalid. Tilapia fry in the first 10-25 days after hatching, that is 7-11 mm in total length, the highest success rate, feeding male feed for less than a month is appropriate. At present, some feed manufacturers are trying their best to launch full-scale male feeds that are extremely irresponsible to farmers and consumers. One is that males do not work on sexual induction at the later stage of culture. The second is the increase in the chance of full-female rations leading to fish fulminant fish disease. Third, the accumulation of male hormones in fish poses a risk to consumers. 4.2.2 Polyculture of predatory fish, juvenile diarrhea Tilapia in tilapia culture, can be appropriately matched with carnivorous fish, can be used with 3-5 Tara argus, white locust and so on. However, FeSO4 cannot be used in the ponds of Wuyi, and trichlorfon, dichlorvos, and malachite green cannot be used in the fish ponds that are used in white turtles. 4.2.3 Selection of male fingerlings Breeding can be conducted manually at the initial stage of breeding. This is a waste of female seedlings. Second, it is time-consuming and the fish is easily injured. 4.2.4 Cage culture of fish, high-density pond stocking The use of tilapia in cages can effectively limit its fertility; in the case of high-density pond culture, the breeding juveniles are devoured by large-scale fingerlings or adults. There is a certain effect. 4.2.5 Collect the young fry in the pond where the second-instar fish is to be thrown, and remove the fry at any time along the pond in the season when the tilapia produces small seedlings. 5. Production of Tilapia Chifeng City Ningcheng County hot-water fish farms have 300 species of tilapia broodstock, with an annual output of 6 million tilapia sprays, 2 tons of fish species and 8 tons of adult fish. Species are rainbow trout and Nile tilapia.
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