Methods and Technical Points for Rearing Black Carp Fry and Fingerlings in Ponds
The black carp is a fish with a bluish-black color, mainly distributed in the plains south of the Yangtze River in China, and relatively scarce north of the Yangtze River; it is an important fishery resource in the middle and lower reaches of the Yangtze River and the lakes along the river, and a major culture species in various lakes and ponds. It is one of the “Four Major Chinese Carps” of freshwater aquaculture in China. In addition, in Anhui it is commonly called “wuhun”, “heihun” or “luosihun”, named for its black body and fondness for eating river snails; the “qingyu” commonly found in Northeast China is not the black carp and should be written as “qingyu” (mackerel), a deep-sea fish. Within China, the largest black carp specimen weighed 218 jin; it was caught in 2005 at Jinniu Lake in Luhe District, Nanjing, measuring 1.86 m in length and weighing 218 jin, and was estimated by scale examination to be about forty years old. The black carp is also called heihuan or luosiqing. Class Osteichthyes, family Cyprinidae. Body subcylindrical, up to more than 1 m in length. Bluish-black, fins grayish-black. Head broad and flat, mouth terminal, no barbels. Pharyngeal teeth molar-shaped. It inhabits the middle and lower layers, feeding mainly on river snails, mussels, shrimp and aquatic insects. It reaches sexual maturity at 4-5 years of age, spawns in the upper reaches of rivers, and can be artificially bred. Individuals are large and grow rapidly, with the largest reaching 70 kg. The flesh is delicious. It is a major freshwater fish culture species in China. It is distributed in all major river systems of China, mainly produced in the plains south of the Yangtze River. The fish gall bladder is toxic.
So how are black carp fry and fingerlings reared in ponds?
Fry rearing
Preparation of the fry pond
1. Disinfection of the fry pond: 15 days before stocking fish, carry out pond clearing and disinfection with quicklime at a concentration of 180 g-230 g/cubic meter or trichloroisocyanuric acid at 3 g-5 g/cubic meter.
2. Fertilization of the fry pond: apply green manure 5 days before stocking; organic fertilizer should be fermented and decomposed, and disinfected with 1%-2% quicklime; 2-3 days after fertilization, deepen the pond water to 0.5 m, and after 5 days deepen it to 0.6 m-0.7 m; when adding water, filter it through a 60-mesh fine net.
Source of fry and fingerlings
Fry obtained from the propagation of black carp broodstock that meets the regulations, or purchased from outside. Their quality should meet the regulations. Purchased fry and fingerlings should have a quarantine certificate from the relevant department. Stocked fry and fingerlings should be uniform in size, robust in constitution, and free of disease and injury.
Fry stocking
Choose a sunny day and release fry 5-7 days after hatching at the windward spot; the stocking density is 60,000-100,000 fish/667 sq m; the water temperature difference when releasing the fry must not exceed 2°C.
Feeding management
Feeding. After the fry are stocked, feed them with soybean milk every day. For the first 5 days after stocking the fry, the amount of soybeans used is 2 kg/667 sq m, and after 10 days increase as appropriate, twice a day, splashing evenly over the whole pond.
During operation, first soak the soybeans in water until soft, that is, at a water temperature of about 25°C, soak them in water for 5-7 hours, then grind 10 kg-15 kg of soybeans with water in one pass into 160 kg-250 kg of soybean milk.
For every 10,000 summer fry fingerlings of over 3 cm raised, 7 kg-8 kg of soybeans and soybean cake and 30 kg-40 kg of manure are needed.
Pond patrol. Observe whether the activity state of the fry entering the pond is normal. If normal, the stocked fry immediately swim and disperse in all directions, and within 1 hour the fry can be observed moving about, swimming regularly, and beginning to feed.
After the fry are stocked, the pond should be patrolled multiple times a day to observe the water quality and the activity of the fish, promptly remove water centipedes, frog eggs, weeds, Spirogyra, water net algae, etc., check the feeding, growth and disease and pest conditions of the fry, take timely measures when problems are found, and keep records.
Water addition in stages. One week after the fry are stocked, water should be added once every 5-7 days, each time deepening by 10 cm-15 cm. When the fish reaches a total length of 3 cm, keep the pond water depth at 1.3 m-1.5 m.
Seine net training. When the fry have been raised for about 25 days and become summer fry fingerlings, they should be thinned and transferred to separate ponds. Before leaving the pond, seining must be carried out. Crowd and train them 2-3 times.
Prevention and treatment of fish diseases. In the early stage of fry rearing, there are fewer fish diseases but more enemies, while in the later stage fish diseases increase somewhat.
In the early stage of fry rearing, the main fish disease is gas bubble disease; the enemies are aquatic insects represented by water centipedes, algae represented by Spirogyra, water net algae and lake bluish-green algae, and even large zooplankton, aquatic grasses and waterside weeds also pose harm to the stocked fry. In addition, wild miscellaneous fish, shrimp, snails, mussels, shellfish, tadpoles, etc. are all enemies of the fry.
In the later stage of rearing, as the fish body continues to grow and its feeding habits change, fish diseases gradually increase, such as common parasitic fish diseases like Trichodina, Chilodonella, and Cryptobia branchialis, and common bacterial fish diseases like white head and white mouth disease and white skin disease.
Rearing of one-year-old fingerlings
Stocking time and stocking density
Stocking time. After the summer fry fingerlings of black carp have been trained by seining, they can be transferred and stocked in separate ponds; when the total length reaches more than 3 cm, they should be stocked even more promptly, and generally stocking should be completed before the summer solstice.
Stocking density. For every 666 sq m of water surface, stock 5,000-7,000 black carp summer fry fingerlings, with 1,200-1,400 silver carp and bighead carp fingerlings as companion species.
Feeding management - feeding
Feed types. The feed for black carp includes soybean milk, soybean residue, soybean cake paste, crushed river snails, yellow clams and black carp compound feed, etc.
Feeding principles. Adhere to the “four fixeds” of “fixed time, fixed location, fixed quality, fixed quantity”:
Fixed time: feed once each day from 8 to 10 a.m. and from 2 to 4 p.m.;
Fixed location: feed should be placed on feeding tables at fixed positions. After the summer fry fingerlings are stocked, first splash around the feeding table, then gradually narrow the range to guide the fish to feed on the feeding table;
Fixed quality: all kinds of feed should be nutritionally complete, clean and hygienic, and moldy and spoiled feed must not be fed;
Fixed quantity: feeding should be appropriate and uniform, and with compound feed it is best if it is eaten within 2-3 hours after each feeding. On rainy days and when fish diseases are prevalent, the feeding amount should be reduced as appropriate.
Feeding amount. In rearing black carp fingerlings, compound feed should be the main feed, with appropriate feeding of animal feeds such as river snails and yellow clams. The feeding amount for rearing black carp fingerlings is shown in the table.
The compound feed for feeding black carp fingerlings should be mixed with water into a paste or moistened into strips and placed on the underwater slope at the pond edge or on feeding tables at fixed positions; if compound pellet feed for fingerlings is used, it is likewise placed on them, making it convenient for the fish to eat and grow normally.
Proportion of monthly feeding amount in the total feeding amount: April 3%, May 4%, June 5%, July 15%, August 23%, September 20%, October 15%, November 10%, December 3%, January to March 2%.
Daily management
Pond patrol. Once the fingerlings are stocked in the pond, daily management begins immediately. Through morning and evening pond patrols, observe water quality changes and fish activity, take corresponding management measures, and keep production records.
Regular water addition. Add new water once about every 15 days, each time deepening the pond water by 10 cm-15 cm (including partial water exchange), keeping the water level at about 1.5 m.
Adjust the feeding amount. Regulate the feeding amount and feeding frequency according to the activity, feeding and growth of the fish and the weather conditions. Control the satiation of the fish at 70%-80%.
Observe the water color and regulate water quality. The water color should be kept greenish-brown or tea-brown, with a transparency of 30 cm-35 cm.
Prevention and treatment of diseases. Fish diseases should be discovered in time and prevented and treated early. Adhere to the principle of prevention being more important than treatment, and do well in the “three disinfections”, namely pond disinfection, fingerling disinfection, and feeding table (feeding frame, feeding ground) disinfection.
Fingerling screening
Starting from early August, seining inspection of the growth of various fingerlings should be carried out every 10-15 days; if the sizes differ greatly, fish screens should be used in time to sort and rear them separately, and the amount of feeding and fertilization should be adjusted to ensure that the pond-out sizes of various fingerlings are uniform.
Pond-out and pond merging of fingerlings
After the fingerlings are screened and classified, they should be carefully verified and classified. When the temperature drops to 10°C-5°C, they should be ponded out for stocking, or merged into ponds for concentrated rearing, or transferred to the rearing of two-year-old fingerlings.
Rearing of three-year-old fingerlings
Stocking density
Stocking density for mainly rearing two-year-old black carp fingerlings. For every 667 sq m of pond, generally stock 1,000-1,200 two-year-old black carp fingerlings, with 200 silver carp and bighead carp fingerlings, 20 grass carp fingerlings, and 200 crucian carp fingerlings (or 300-500 yellow catfish) as companion species.
Stocking density for mainly rearing three-year-old black carp. For every 667 sq m of pond, generally stock 380-420 three-year-old black carp fingerlings, with 200 silver carp and bighead carp fingerlings, 20 grass carp fingerlings, and 200 crucian carp fingerlings (or 300-500 yellow catfish) as companion species.
Feeding management
Mainly feed animal feed and compound feed, with plant feed as a supplement. The feed should be nutritionally complete and fresh, and meet the provisions of feed hygiene standards. During the high-incidence seasons in spring and autumn, appropriately increase easily digestible food, and the feeding ground area should be larger. Keep the water quality fresh, and frequently disinfect the feeding ground with drugs or use medicated bait to prevent and treat enteritis.