Detailed Explanation of Key Technical Points for Bighead Carp Cage Culture
Cage fish farming technology is a three-dimensional aquaculture technique that makes full use of reservoir resources. It has the advantages of low farming cost and high benefits, and is deeply favored by the vast number of fish farmers. Among them, the technique of using cages to culture bighead carp is one of the most profitable among many farming projects.
How to Culture Bighead Carp in Cages
1. Get the cage structure right. The cage material is polyethylene, the netting twine diameter is 1.13 mm, the mesh size is 3-5 cm, and a cage specification of 4 m×7 m×2 m is more suitable. Use a single-layer cage, with a frame made of bamboo poles about 10 cm in diameter, several of them connected as one unit, and use sinkers to fix the cage position so as to prevent drifting.
2. Placement. The placement of the cage is extremely important and directly affects the growth rate of bighead carp. Generally, it is advisable to place it in a reservoir area with broad waters, slight water flow, good water quality, no pollution, abundant sunlight, shelter from wind and facing the sun, relatively high water temperature, sufficient bait organisms, relatively close to the shore, a water depth of 4-7 m, relatively little wind, and convenient transportation.
3. Scientifically stock fingerlings. The best time for stocking fingerlings is November-December each year, or February-March of the following year, when the water temperature is relatively low, transportation is convenient, the fish body is less injured, and the survival rate is high. The stocking specifications are about 80 g or about 350 g respectively. For 80 g fingerlings, stock 450-550 per cage; for 350 g fingerlings, stock 200-250 per cage. The stocked fingerlings should be guaranteed to be robust and uniform in specification, and strictly disinfected before and after entering the cage to prevent the occurrence of saprolegniasis and death. Before the fingerlings enter the cage, because transportation and loading cause injury to the fish body, saprolegniasis is very likely to occur under relatively low water temperature conditions.
4. Careful management. For the success or failure of cage culture of bighead carp, feeding management is very important. Good management can accelerate the growth of bighead carp, increase yield, and obtain better economic benefits. Otherwise, due to poor management, growth is slower, the incidence of disease is high, and the fish may even escape, resulting in farming failure. Feeding management mainly includes the following aspects:
1) Soaking the cage. New cages have a rough surface, and directly loading fish can easily cause injuries to the fish body surface. Therefore, they must be soaked in the reservoir 7-10 days in advance to let the netting twine soften.
2) Brushing the cage. After the cage is placed in the reservoir, due to the action of plankton in the water, much dirt adheres to the cage, affecting water exchange and causing a decrease in the number of plankton in the cage, so that bighead carp grow slowly due to a shortage of bait organisms. Therefore, the cage must be brushed and washed frequently. Generally, during the growing season, brush and wash once every 15-20 days.
3) Moving. There are two situations for moving. First, during the flood season, move the cage to prevent it from being destroyed by floods and strong winds. Second, by moving the cage, increase the content of bait organisms in the cage and accelerate the growth of bighead carp.
4) Feeding. If the reservoir water body is relatively lean or there are many cages, and other methods cannot increase the bait organisms in the cage, then it is necessary to pile or hang organic fertilizer or chemical fertilizer around the cage. Chemical fertilizer is hung in windless conditions.
5) Dividing the cage. After one year of culture, most fingerlings grow 10-20 times. In the spring of the following year, in order to ensure the normal growth of fish in the cage and avoid insufficient dissolved oxygen and bait in the cage, cage division must be carried out to ensure growth space.
6) Inspection and care. During the growing season, the cage needs to be checked frequently to observe the activity of the fish, and measures should be taken promptly when problems are found to prevent the fish from escaping. In winter, fish not yet sold should be gathered together for supervision to prevent strong winds from breaking the cage or theft.
5. Marketing and sales. By late autumn, when the reservoir water temperature drops to 10\u2103, bighead carp have stopped growing, and harvesting and selling of bighead carp begins. At this time, stocked 100 g bighead carp can grow to more than 500 g, and each cage can produce a net yield of more than 200 kg of bighead carp; after cage division the following year, they can grow to more than 1,500 g. Stocked 350 g bighead carp can grow to 1,000 g, and each cage can produce a net yield of more than 250 kg of bighead carp; after cage division the following year, they can grow to more than 2,500 g, and the farming benefits are very considerable.
Living Habits of Silver Carp
1. Feeding habits: Silver carp is a mid-upper layer fish and feeds on plankton throughout its life. At the fry stage, it mainly eats zooplankton. When it grows longer than 1.5 cm, it gradually shifts to eating phytoplankton, and it likes to eat the feces of grass carp and the applied chicken and cow manure. It is very interested in sour foods and also has a good appetite for distillers' grains feed. Its bait has obvious seasonality. In spring and autumn, in addition to plankton, it also eats large amounts of detritus-type bait. In summer, the lower the water level, the greater its food intake; in winter, it overwinters with little eating and little movement.
2. Water temperature: Silver carp likes high temperatures, and the most suitable water temperature is 23-32\u2103. In hot summer, the appetite of silver carp is most vigorous. It has a lively temperament, likes to jump, and has the habit of swimming upstream, but its movements are not very agile and it is relatively clumsy. Silver carp likes fertile water, and individuals of similar size often gather and swim in schools to the middle and upper layers of the water, especially in clear-water areas with relatively fertile water quality. It is timid and afraid of disturbance, and its tolerance to low oxygen is extremely poor. When there is insufficient oxygen in the water, it immediately surfaces to gasp, and some soon die.
3. Reproduction: Silver carp grows fast and has high yield. Its sexual maturity age is 1-2 years earlier than that of grass carp, and mature individuals are also smaller. Generally, female fish above 3 kg can reach maturity. A female fish of about 5 kg has a relative fecundity of about 40,000-50,000 eggs/kg body weight. It spawns in April-May each year, and the eggs are floating eggs. Under pond culture conditions, if bait is sufficient, the fish of the year can grow to 500-800 g, and three-year-old fish can reach 3-4 kg in body weight. In natural rivers, it can reach 30-40 kg.
Nutritional Value of Bighead Carp
Bighead carp is sweet in taste and warm in nature, and can warm the stomach, tonify deficiency, resolve phlegm, and relieve asthma. It is suitable for symptoms such as deficiency-cold of the spleen and stomach, excessive phlegm, and cough. People with weak constitution had better eat more bighead carp fish head; its warming and tonifying effect is very good, and it can also play a role in treating tinnitus and dizziness. People with excessive phlegm and dizziness can cook and eat bighead carp together with tofu.
Bighead carp has a protective effect on the cardiovascular system. It is rich in phospholipids and posterior pituitary extract that improves memory. In particular, the brain marrow content is very high. Regular consumption can warm the stomach, eliminate dizziness, benefit intelligence, aid memory, delay aging, and moisten the skin.
Culture Technology of Silver Carp
1. Selection and retention of broodstock: Select natural original species for broodstock, requiring health and good gonadal development. Individuals should weigh more than 6 kg for silver carp, more than 10 kg for bighead carp, more than 15 kg for black carp, and more than 8 kg for grass carp. The annual renewal rate of broodstock should reach about 10%.
2. Clearing and preparing the fish pond: The broodstock pond should have convenient irrigation and drainage. For silver carp and bighead carp ponds, a bottom mud depth of 20 cm is sufficient. For black carp and grass carp ponds, the bottom should contain little or no mud. The area is 1-5 mu, the water depth is about 1.5 m, and the pond should be cleared before stocking.
3. Mixed stocking: The ratio of female to male silver carp, bighead carp, black carp, and grass carp broodstock is generally 1:1-1.5. At the same time, stock 8-10 mandarin fish and about 150 bighead carp per mu to control the breeding of wild trash fish and large zooplankton.
4. Feeding management: Before stocking, 500-700 kg of decomposed organic fertilizer should be applied per mu to silver carp and bighead carp broodstock ponds to cultivate plankton, and appropriate fertilization should continue afterward. In addition, soybean cake slurry should be fed in clear and warm weather to promote gonadal development.
5. Early induced spawning: When the female fish's abdomen is enlarged and the genital pore is relaxed, induced spawning can be carried out. Generally, female fish are injected with 1,000 international units of chorionic gonadotropin per kg body weight, or 40-50 micrograms of LRH-A, and male fish receive half the dose.
6. Incubation management: Incubation water should be filtered with a filter net to prevent floating matter and wild trash fish from entering. Before each incubation, clean the incubation jars and incubation troughs. During incubation, provide a suitable water flow rate, and frequently turn the water body to check whether eggs and fry have accumulated at the bottom corners, and maintain water quality.
In China, bighead carp farming is relatively common, and there are many techniques for bighead carp farming. Cage culture is also one of the more commonly used methods. Therefore, farmers can exchange with one another and learn from each other's experience and techniques, so that farming can be done better.