How to farm silver carp? A full analysis of high-efficiency farming techniques
Silver carp is one of the famous Four Major Chinese Carps, also known as white carp, water carp, jumping carp, etc. It is a typical filter-feeding fish. At the fry stage it mainly eats zooplankton, and when it grows longer than 1.5 cm it gradually switches to eating phytoplankton. It also eats soybean milk, soybean residue powder, wheat bran and rice bran, and it prefers artificial micro-pellet compound feed. Let us take a look together at the high-efficiency farming techniques for silver carp.
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, and when it grows longer than 1.5 cm it gradually switches to eating phytoplankton, and it likes to eat the feces of grass carp and the chicken and cattle manure that is applied. It is very interested in sour foods and also has a good appetite for distiller's grains feed. Its bait has obvious seasonality; in spring and autumn, besides plankton, it also eats large amounts of detritus-type feed. In summer, the lower the water level, the greater its food intake; in winter it eats little and moves little during overwintering.
2. Water temperature: Silver carp likes high temperatures, and the most suitable water temperature is 23-32°C. In hot summer, the appetite of silver carp is at its strongest. It is lively in temperament and likes to jump, and has the habit of swimming upstream, but its movements are not very agile and it is rather 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 body, 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 oxygen in the water is lacking it immediately surfaces to gasp, and some die quickly.
3. Reproduction: Silver carp grows fast and has high yield. Its age of sexual maturity 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 of body weight. It spawns from April to May each year, and the eggs are pelagic. Under pond culture conditions, if feed is sufficient, the fish of the year can grow to 500-800 g, three-year-old fish can reach 3-4 kg in body weight, and in natural rivers they can weigh as much as 30-40 kg.
Farming techniques for silver carp
1. Selection and retention of broodstock: Select natural original stock for broodstock, requiring health and good gonadal development. The individual weight of silver carp should be above 6 kg, bighead carp above 10 kg, black carp above 15 kg, and grass carp above 8 kg. The annual replacement rate of broodstock should reach about 10%.
2. Clearing and preparing the fish pond: Broodstock ponds must have convenient irrigation and drainage. For silver carp and bighead carp ponds, a bottom silt depth of 20 cm is sufficient; for black carp and grass carp ponds, the bottom should contain little or no silt. 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 male-to-female ratio of 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, on clear and warm days, soybean cake slurry should be fed to promote gonadal development.
5. Timely early induced spawning: When the female fish's abdomen is distended and the genital pore is relaxed, induced spawning can begin. Generally, female fish are injected with 1000 international units of chorionic gonadotropin per kg of body weight, or 40-50 micrograms of LRH-A, and male fish receive half the dose.
6. Incubation management: The incubation water must be filtered through a filter screen 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, frequently turn over the water body to check whether eggs or fry have accumulated in the bottom corners, and maintain water quality.
Disease prevention and control of silver carp
1. Branchiomycosis
[Symptoms] Sick fish do not feed and swim slowly. The gills show congestion and hemorrhage, the gill filaments are somewhat congested, and they lose their normal bright red color and appear pink or pale. In severe cases the gill filaments necrose, affecting respiratory function and leading to death of the sick fish.
[Prevention and control] ① Thoroughly clear the pond and disinfect it, keep the water clean, and prevent water quality deterioration. ② To cultivate water quality, apply fermented and decomposed organic fertilizer; do not apply it raw. ③ In affected ponds, quickly add fresh water to improve water quality, or transfer the sick fish to ponds with fresh, clean water. ④ Sprinkle 20-30 mg/L quicklime over the whole pond, which can reduce the organic matter content in the water and improve water quality.
2. Print disease
[Symptoms] Sick fish have nearly round red spots on the body surface behind the dorsal fin. Scales fall off at the lesions, and finally ulcers form, even exposing bones or internal organs.
[Prevention and control] ① When applying the feces of herbivorous animals to fish ponds, it must be mixed with quicklime and fully fermented, and only applied after it is decomposed, to prevent pathogens from entering. ② When fingerlings are transferred between ponds, they can be soaked in 2% salt water for 5-10 minutes, which can effectively prevent this disease. ③ Sprinkle 0.5 ppm of Jun Du Qing or 0.3 ppm of dibromohydantoin over the whole pond.
3. Dactylogyrus disease
[Symptoms] When the disease is severe, the gill filaments of sick fish swell and mucus increases, and breathing becomes difficult, which can cause mass death of fry and fingerlings.
[Prevention and control] ① Sprinkle 0.3-0.7 ppm of 90% crystalline trichlorfon over the whole pond. ② Sprinkle Chong Sao Jing at 130-170 mL/mu/m over the whole pond; in severe cases it can be used again every other day.
4. Bothriocephalus disease
[Symptoms] From the external appearance of affected silver carp, the abdomen is distended with local bulging. After the ice melts in early spring, the body condition is noticeably thin, and the abdominal distention becomes even more obvious, with extremely thin abdominal muscles. When the abdomen is pressed firmly, sparganum can emerge from the pectoral fin area.
[Prevention and control] ① Do a good job at the fry stage; before fry are stocked into ponds, the first intermediate host, copepods, must be killed. ② In areas where tapeworm disease occurs frequently, quicklime must be consistently used to clear the pond.