Tilapia is a tropical fish. Its cold resistance is relatively poor. When the water temperature drops to 12°C, frostbite or freezing death occurs. In China, except in parts of Hainan, Taiwan, Yunnan, and Guangdong, where natural wintering can occur, tilapia in most areas cannot overwinter in natural environments and winter winter measures must be taken. The tilapia wintering pond built by Guangxi Fisheries Research Institute at Nama Freshwater Test Base is a hot spring pond with an average water depth of 1.8 to 2.2 meters. The outlet water temperature is maintained at 18 to 20 degrees Celsius all the year round, and some of the smaller wintering ponds In the absence of any other insulation measures, the winter water temperature is only 8 °C ~ 12 °C minimum. Tilapia broodstock has its special status. It is related to the production of seedlings in each tilapia fingerling farm in the coming year and even later. It can even be said to be directly related to the survival of a fish farm. Therefore, perfecting the wintering pond insulation measures is an important task in the management of tilapia wintering.
There are many wintering methods for tilapia, which vary according to the climate and wintering conditions. Since the Guangxi Institute of Fisheries in 2000 contacted tilapia broodstock winter management, it has adopted many wintering measures, including increasing the hot spring water cycle, or putting a shed over the water in the corner of the pond, or setting up a plastic film greenhouse for ponds, etc. Practice, found that the construction of pond plastic film greenhouse is a more successful wintering technology. In view of this, I would like to organize some of the operating procedures for reference.
Preparation before winter
Overwinter ponds are prepared for wintering. The pond area is 2,000 square meters to 2660 square meters, and the water depth is 1.5 meters to 2.4 meters. Each pond is equipped with an aerator (1.5 kW). In the first half of winter, the clear pond is cleaned with bleach. Since it is a hot spring pond, the pond water should be pumped to a minimum, and immediately clear the pond with an increased dose of bleach. Clear water after the pond is full, drain out, repeat twice, 5 days to 7 days after the fish can be tested. Due to the fact that the water quality will be more difficult to manage, the wintering pond water does not require the cultivation of fertilizer.
The preparation and construction of overwintering materials is mainly done as scaffolding arches. In the middle of Datang, wood piles are used to form a row of support frames. Then a small steel wire is placed on the top and the pond is fixed with wooden stakes. After the film is covered, the wire ropes are pressurized. Secure the upper and lower wire ropes with a small wire. Keep the film flat when covering the film to prevent rain from accumulating on the shed when it rains. During the winter, it is necessary to constantly check the film for loopholes and take appropriate measures in time.
Preparation of overwintering equipment is mainly to prepare oxygen, sewage and other equipment to be ready, such as aerators, water thermometers, water pumps, sewage filters and so on.
Prepare the broodstock before entering the pond
One month before wintering, the fattening and cultivating of the broodstock was strengthened, which promoted the growth of the broodstock, enhanced the ability of overwintering and resisting the cold, and gradually adapted to the living environment during the winter, and eliminated some of the broodstock that were weak or injured in advance.
When the broodstock is selected for pro-fishing, it must be carefully selected according to the requirements of the production seedlings to ensure that each broodstock meets the requirements. The proportion of male and female broodstock is selected according to the ratio of 2:1 or 3:1, and the male and female ponds will be overwintered to facilitate the mating operation in the coming year. The number of retained elections will increase by 15% to 20% on the basis of the planned amount of production fry to ensure that the seed production in the coming year reaches a predetermined plan. The operation must be light and careful so as not to injure the fish body, and to pay attention to the fish species that escape the screen.
When the fish body is disinfected over the winter, the broodstock must have varying degrees of injury during transportation and operation. Before the pond is unloaded, the fish body should be disinfected with drugs. The fish body can be soaked with 2%~3% salt solution for 5min~10min and then down the pond. Prevent disease from happening. Within one week after entering the pond, close attention should be paid to the activities of the broodstock in the pond, especially if the broodstock's wounds are infected when the water temperature is low, and appropriate measures shall be taken in time. One week after entering the pond, the situation of broodstock was basically stable and it was managed during the wintering period.
Time and density of broodstock entering the pond
According to the climate change, the time of entering the pond can be selected from the end of October to the beginning of November in the local pond. The water temperature is suitable when the water temperature is 20°C~22°C. Pro-fish into the pond should be selected in the weather is stable, there are strong sunshine days, generally in the 9:30 ~ 16:30 operation, the higher temperature during this time, favorable for broodstock.
Stocking Density The density of broodstock entering the pond depends on the conditions of the wintering environment, fish size and management level. Wintering in the film, Datong, hydrostatic oxygen, generally can be placed broodstock 3kg ~ 5kg / cubic meter, but because the broodstock in the late winter period in the original pond before the seedlings to strengthen the cultivation, so the conditional unit should reduce the parental stocking density. The wintering pond in this test is a hot spring pond with convenient drainage and drainage. The stocking density is relatively large, ranging from 2800 to 3000 tails/mu, and the specification is 500 to 600 grams/tail. If you consider pairing seedlings in the original overwintering greenhouse, consider the number and weight of the female and male parent.
Feeding management during wintering
Tilapia has a relatively long wintering period, usually from the end of November to late March in Guangxi, which lasts for about 4 months. In production, winterization is generally divided into three stages, namely, early winter, mid-winter and late winter. In the early winter and when the water temperature is about to exit the pond, the temperature of the water should be higher and the water quality should be appropriately adjusted. In the middle of winter, the temperature should be reduced. Feeding should be appropriately reduced to prevent the deterioration of water quality. The management of the late winter is particularly important. Before going out of the pond, it is necessary to strengthen the quantity and quality of the feed to promote the recovery of the physique of the broodstock and the development of the gonadal. This ensures that the broodstock will begin to grow and grow in a relatively short period of time after leaving the pond. Throughout the winter, there must be someone responsible for doing a good job of recording, controlling water temperature, regulating water quality, feeding materials, and preventing diseases.
The water temperature controls the broodstock in the early period of the pond. The water temperature of the hot spring pond can be controlled by adjusting the amount of the hot spring water. When the broodstock enters the pond within 10 days, the water temperature should be controlled between 20°C and 25°C. This will help the fish body's wounds heal as soon as possible and inhibit the occurrence of watery mildew. After the situation is basically stable, the water temperature can be controlled between 18°C ​​and 20°C. The water temperature cannot be changed too quickly, it cannot be suddenly cooled, nor can it be controlled for more than 20°C for a long period of time. Long-term high temperature is not conducive to overwintering management. Because the water temperature is high, the fish’s ability to move is strong, and the amount of food consumed is increased, thereby increasing feed intake. With the investment, the water quality will also deteriorate rapidly. The use of plastic film greenhouses, due to the increase in temperature during daytime sunlight, greenhouse temperature sometimes up to 30 °C, the water temperature will rise accordingly, this time the film should be opened part of the air circulation, the greenhouse temperature is controlled at around 22 °C The water temperature is controlled at 18°C~19°C. Whenever there is a sudden change in the weather or in the event of a sudden change in the weather, the film should be covered in time.
Water quality regulation overwintering ponds should keep fresh water and sufficient dissolved oxygen. During the winter, the water quality can be adjusted and the vitality of water can be increased by regularly using a number of microbial preparations, such as vitamins and cultured treasures. When the water becomes thick, you can drain away 1/4 to 1/5 of the old water. If the water color is still too strong, change the water again after 3 days to 5 days. The outlet must be covered with a strainer to prevent miscellaneous fish from swimming backwards into the pond.
Oxygenation measures wintering ponds are generally higher in density and must be equipped with aerators. In the cold season, due to the lower surface water temperature, the pro-fish anoxic floating surface exposed after the water surface, very prone to frostbite, resulting in the gradual death of S. muridae. In the late winter, due to the increase of water temperature, the feeding amount will increase, and the broodstock will become fat during the prenatal culturing process, which will result in severe hypoxia and affect the cultivation. Therefore, oxygenation during the winter is very important. An aerator can be opened around 23:00, and the next day at 9:00, it is possible to extend the boot time by running into a rainy day. In order to prevent power outages and other accidents, it is also necessary to prepare pumps, generators, oxygenating agents, etc.
Proper feeding of broodstock should be properly fed with nutrient-rich concentrate during the winter and supplemented with quantitative green fodder (ie, greens). Usually take more than two, feeding less in the middle way. In the early winter period, feed more properly and feed twice a day. The daily feed amount is about 2%, and a small amount of green feed is fed. Try to feed the whole pond as much as possible so that all fish can eat. The broodstock will continue to receive more nutrients during this period to accumulate enough fat to cope with the arrival of the cold season. During the middle of winter, when the water temperature is low and the broodstock activity is reduced, the amount of feeding must be reduced. At this time, the adjustment can be made according to the feeding condition of the broodstock, and it is advisable to eat within 1 hour. In the late winter, the water temperature rises and the broodstock activity increases. This period is also the prenatal incubation period. At this time, feeding should be adjusted according to the broodstock's shape, plumpness, and gonadal development. If the broodstock is thin and the gonadal development is not good, the amount of feed must be increased. If the broodstock body shape is partial fat, it will not be conducive to the emergence of seedlings after the pond, must increase the amount of green feed, reduce the amount of pellet feed.
Daily management
Pay attention to the temperature change and measure the water temperature and temperature in the morning and evening. Pay special attention during the cold, rainy season.
Adhere to the early, middle and evening patrol pond inspection whether the shed is solid, rainy days to promptly let go of the roof of the water, to prevent the shed can not withstand heavy pressure and collapse. Observe the broodstock's vitality and food intake regularly, monitor the wintering ponds' dissolved oxygen, ammonia nitrogen, organic matter, etc. regularly, make records, and identify problems and take timely measures.
Pay attention to ventilation and ventilation In good weather days, the temperature in the greenhouse often rises quickly at noon, sometimes up to 30°C or more, and the air will be dull. At this time, it is necessary to turn a part of the membrane open to cool down because of ventilation. The rapid increase in temperature will lead to a corresponding increase in water temperature. During the overwintering period, the increase in water temperature must be controlled within a certain range, otherwise the brooders will be released from overwintering in advance, and will enter the overwintering state the second time when the water temperature is declining, which is not conducive to overwintering and management of broodstock. In the afternoon, cover the film.
Pay attention to the prevention of disease over the winter season, due to the small pond area, high density, low water temperature, coupled with less activity and less feeding, broodstock easier to get sick. Therefore, we must adopt the principle of prevention and prevention. During the overwintering period, choose a strong noon with strong sunlight. Every half a month, whole ponds will be splashed with lime for 1 time. The usage volume will be 10 kg to 15 kg/mu. After 7 days to 10 days, the concentration of 0.25 ppm to 0.30 ppm of carbon dioxide will be used. Chloride Quantang spilled once. Always check the activities of broodstock, find abnormalities, and deal with them promptly.
Conclusion
Due to its importance, tilapia broodstock makes its wintering a major task in winter management of various tilapia fingerlings. In Nanning, the average depth of a pond is generally more than 2 meters. Tilapia can spend most of its wintering time safely. However, there will always be a very low temperature for a period of time. The duration lasts from 10 days to 15 days, and sometimes up to a month. Tilapia's frostbite and even death will occur during this time. Therefore, it is not possible to carelessly or arbitrarily exist, and do a good job in protecting winter tilapia. The construction of pond plastic film greenhouses for tilapia broodstock wintering is currently a relatively broad approach.
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