Artificial Breeding Methods and Breeding Environment Requirements for Sea Bass
Sea bass is one of the common commercial fish. Its flesh is delicious and rich in nutrients such as protein, vitamins, niacin, phosphorus and iron. It can tonify the liver and kidneys, strengthen the spleen and stomach, and can treat conditions such as restless fetal movement and insufficient milk after childbirth. Sea bass has the characteristics of fast growth, wide adaptability and strong disease resistance. It naturally feeds on small fish and shrimp, and artificial breeding offers high economic returns. So how do you carry out artificial breeding of sea bass? What are the requirements for the breeding environment?
1. Breeding environment requirements
The area of a sea bass breeding pond should not be too large. If the pond is too small, the water body is narrow and dissolved oxygen is insufficient, making high yield difficult; if the pond is too large and too deep, it is not conducive to production operations.
A pond of 8~12 mu with a water depth of about 2 m is suitable, with sandy loam soil as the bottom material, relatively little silt, a flat pond bottom sloping slightly toward the drainage outlet, a water depth of 1.54 m, a complete drainage and irrigation system, and sufficient, fresh, pollution-free water of good quality. The pond should preferably be equipped with inlet and outlet sluice gates leading respectively to the inlet and outlet rivers, without reusing the aquaculture water, so as to avoid secondary pollution.
Use fine nets to divide the pond into smaller sections to make it easier for fry to feed. Equip 1 aerator for every 1.2~1.5 mu of water surface, and also configure a water pump to ensure that new water can be replaced at any time, as well as a diesel generator to prevent pond oxygen deficiency during power outages.
Ponds used for breeding sea bass must undergo pond drying, dredging and sun exposure before fry can be released. Disinfection should be carried out half a month before fry release: apply 150 jin of quicklime per mu or use 20 mg/L bleaching powder with an appropriate amount of pond water for disinfection. If the pond has not been dried and sun-exposed, crushed tea seed cake should be soaked in water and splashed over the entire pond; if it has already been dried and sun-exposed, release about 10 cm of water 10~15 days before stocking, use 80~100 kg of quicklime per mu, and the next day add 5 kg of bleaching powder, dissolve in water and splash over the whole pond for pond clearing and disinfection, and thoroughly remove wild and miscellaneous fish.
2. Rearing and stocking fry
The fry release period is from early December each year to March of the following year. Sea bass fry caught from sea areas with a body length of 1.5~2 cm must be desalinated to a salinity of 4‰~7‰ before being put into a temporary holding pond with a salinity of 1‰ for transitional holding. The general stocking density is about 8,000 fry per mu. Choose midday on a sunny day to release the fry, when the water temperature and dissolved oxygen are higher, which can reduce discomfort to the fry. After disinfection with water, the fry are placed into the prepared mesh enclosures. Because high-density breeding involves heavy feeding, and sea bass rarely seek leftover bait at the pond bottom, after removing the nets, a small number of crucian carp, tilapia or bream (omnivorous) should be stocked per mu, along with a small number of bighead carp (filter-feeding), to reduce water pollution and increase breeding benefits.
Starting from the second day after being put into the pond, feed live bait such as zooplankton and bloodworms. Gradually mix fish paste and floating pellet compound feed with the live bait, then gradually acclimate them to being fed minced fish surimi and floating pellet feed. During the temporary holding period, splash 0.3 international units of strong chlorinated disinfectant or 15 international units of formalin for disinfection once a week. For 3 days before starting bait feeding, administer orally per 50 kg of fish 0.5 g of furazolidone, 3 g of oxytetracycline and 1 g of vitamin C, mixed into the feed once daily.
After more than 20 days of rearing, when they grow to 4~6 cm, they are screened and divided into ponds by size for rearing. The stocking density is generally 2,500~3,500 fry per mu, with a water depth of more than 1.5 m, maintaining suitable pond water fertility, with a transparency of 30 cm and a water color of oily green being suitable. Feed twice daily, mainly with minced fish surimi and floating pellet feed. Vitamin B and C should be added to the feed, with a daily feeding amount of 6% of the fish body weight. Mix oxytetracycline, erythromycin and vitamin drugs into the bait and feed twice a month, each time for 3 consecutive days, and regularly splash 0.4 international units of strong chlorinated disinfectant or 20 international units of formalin over the entire pond for disinfection. Carry out pond patrol management well every day, turn on aeration when air pressure is low at night, and promptly drain and replace water if pond water deteriorates, keeping the pond water fresh.
After releasing the fry, turn on sufficient aeration, preferably using air diffuser stones for bottom aeration. Generally no bait is fed on the first day, and after one day, feeding and feeding training begin gradually, requiring fixed locations and fixed times, generally 4 meals. The best opening bait is water fleas, or fish paste mixed with part of eel feed can also be used as opening bait. When the fry reach 5~6 cm, expanded feed can be gradually fed. During the fry stage, enteritis-preventing drugs should be appropriately added to the feed, and the mesh enclosures should be gradually removed as the fry grow.
3. Strengthen daily management
When sea bass fry are reared to a body length of about 10 cm and placed into ponds for adult fish breeding, the survival rate is high. The stocking size should be as uniform as possible to prevent them from cannibalizing each other. The suitable stocking density is 1,000~1,500 fish per mu, along with 40 large-size bighead carp fingerlings, 20 silver carp fingerlings and 200 Pengze crucian carp, to make full use of the water body, regulate water quality and increase yield.
September to October, when the temperature is suitable, is the rapid fattening stage for sea bass, and water quality regulation must not be neglected. After disinfection, the pond is filled with fresh water filtered through a net, with a water depth of about 80 cm, and some compound fertilizer is applied to cultivate plankton. Sea bass is a bottom-dwelling fish that likes to live in clean water with relatively high dissolved oxygen (4~6 mg per liter, transparency of 30~40 cm). New water should be added flexibly and promptly according to water color and transparency. In the early stage, because the fish are small and the temperature is low, water quality is easy to control, so the cycle for adding and changing water can be longer. As the fish grow and the pond biomass increases, pond patrols should be done frequently, new water should be injected often, and aerators should be used reasonably for aeration.
Feeding must achieve “fixed location, fixed time, fixed quantity”. Generally, feed 2 meals a day, at 6~7 in the morning and 6~7 in the evening respectively. A feeding bridge should be set up in the pond, and each meal should normally be fed until about 80% full. In case of high temperatures or cooling, the feeding amount should be appropriately reduced. At each feeding, pay attention to observing the fish school's feeding and health status, so that timely countermeasures can be taken. Water quality should be kept fresh and dissolved oxygen sufficient. When breeding density is too high, a large amount of leftover bait and excrement tends to remain at the pond bottom, and harmful substances decompose at high concentrations, consuming large amounts of oxygen in the water. As the fish grow, increase the frequency of turning on the oxygen machines. Biological agents can also be appropriately applied to effectively degrade ammonia nitrogen and nitrite and maintain good water quality. At night, especially from 2~3 in the morning, inspect the operation of the aerators.
4. Scientific disease prevention
Sea bass are prone to overeating and are susceptible to enteritis. During the day, observe changes in the sea bass's feeding to judge their health status. Sick fish have a swollen abdomen and red and swollen anus, and when the abdomen is pressed, pale yellow mucus flows out. This is caused by feeding spoiled feed or overfeeding. The feeding amount should be appropriately controlled, which helps reduce costs, avoid polluting water quality and reduce the occurrence of gastrointestinal diseases. For treatment, first reduce the feed, preferably skipping one meal, and feed broad-spectrum antibacterial drugs mixed into bait for 3~5 days to recover. At the same time, inspect whether any fish are swimming at the surface. Generally, before a large-scale outbreak, a small number of fish will swim at the surface. This is the best time for diagnosis and medication, and also a key period for prevention.
In autumn, hepatobiliary syndrome is prone to occur, mainly manifested as reduced feeding, followed gradually by fish swimming at the surface and unexplained deaths. The main cause is frequent application of drugs under high-density breeding, with toxic and harmful substances in the water body chronically accumulating in the fish, leading to organ dysfunction and tissue damage. Or it may be caused by long-term overfeeding, with the fish liver under long-term overload leading to metabolic disorder and metabolic chaos. The water environment should be well regulated, feeding should be scientific, and regularly feeding Chinese herbal medicines for soothing the liver and promoting bile secretion mixed into the feed has a certain preventive effect.
Parasitic diseases are prone to occur in autumn, so disinfection and deworming work should be done well. Generally, disinfect once every 15 days, with the frequency depending on the fish's feeding condition. Parasitic diseases mostly occur on the body surface and gill filaments of fish during the intermediate rearing stage, manifested as emaciation, darkened body color and erosion at the mouth end.
Generally, parasites easily cause secondary bacterial infections, so disinfection is generally required after deworming. Prevention is mostly carried out by changing water to improve water quality. For treatment, 0.77~1 mg per liter of a copper sulfate and ferrous sulfate mixture (5:2) can be evenly splashed over the whole pond, or 20~25 mg per liter of formalin can be splashed over the whole pond.