Key Technical Points for Pollution-Free Pond Farming of Black Carp

Black carp, also known as qing huan, luosi qing, hei huan, or gang qing, is one of China's four major domestic carps and belongs to the subfamily Leuciscinae of the family Cyprinidae, order Cypriniformes. Its body is cylindrical, with a laterally compressed tail and a rounded belly; the back and the upper half of the flanks are blue-black, the belly is milky white, and all fins are grayish-black. It is a bottom-dwelling carnivorous fish; the fry mainly feed on zooplankton, chironomid larvae and nauplii, while at the adult stage it prefers snails, mussels, small fish, small shrimp and aquatic insects. Under artificial farming conditions, various compound feeds can be given.

The black carp is large-bodied, thick-fleshed, rich in fat, delicious, with few intermuscular bones, and highly nutritious: every 100 grams of flesh contains 19.5 grams of protein and 5.2 grams of fat, along with large amounts of vitamins and zinc. It is a top-grade freshwater fish and has the best flesh quality among the four major domestic carps, with very high economic value; pollution-free farming of black carp has broad prospects for development.     I. Farming Environment Requirements     The farming environment includes the atmospheric environment, the water environment for fish growth, and the water quality of fishery water sources, etc. The farming environment must comply with the provisions of the national standards "Safety and Quality of Agricultural Products - Environmental Requirements for the Production Area of Pollution-Free Aquatic Products" (GB/T184074-2001), "Water Quality Standard for Fisheries" (GB/T11607-89), and "Pollution-Free Food - Water Quality for Freshwater Aquaculture" (NY5051-2001).     1. Selection of Farming Waters Black carp farming waters should be chosen in areas with a good ecological environment, sufficient water sources, and no or no direct pollution from industrial “three wastes” as well as agricultural, urban domestic, and medical waste. Within the farming waters, as well as upwind and upstream of the irrigation water source, there should be no pollution sources that pose a threat to the farming water environment.     2. Removing Excess Pond Silt Silt is composed of dead organisms, leftover feed, feces, various organic debris, and various organic matter and soil sediments. Through bacterial decomposition and ion exchange, they continuously dissolve and release into the water, providing nutrients for the reproduction of feed organisms. However, too much silt will produce large amounts of hydrogen sulfide, methane, organic acids, low-grade amines, and mercaptans; when these substances accumulate in the water, they affect the health and growth of black carp. Therefore, excess silt should be removed. The specific measure is to drain the pond water every one or two years of farming and dig out the excess silt, so that about 20 cm of silt is retained at the pond bottom, which is more suitable. At the same time, let the pond bottom be exposed to the sun and frozen, to kill pests, parasites, and pathogenic bacteria.     3. Disinfection of Pond Water Body To improve the pond environment, eliminate harmful organisms, and prevent some bacterial diseases, the pond and its water body must be disinfected. Common disinfectants and their dosages are as follows: (1) Use quicklime at a concentration of 200 mg~250 mg per liter for clearing the pond with water, or use quicklime water at a concentration of 20 mg~25 mg per liter for whole-pond splashing disinfection; (2) Use bleaching powder at a concentration of 20 mg per liter for clearing the pond with water, or use bleaching powder water at a concentration of 1.0 mg~1.5 mg per liter for whole-pond splashing disinfection; (3) Use sodium dichloroisocyanurate solution at a concentration of 0.3 mg~0.6 mg per liter for whole-pond splashing disinfection; or use trichloroisocyanuric acid solution at a concentration of 0.2 mg~0.5 mg per liter for whole-pond splashing disinfection.     4. Water Quality Management The water environment is the basis for the black carp's life and growth in the pond, and all fish-farming measures act on the fish body through the environment. Therefore, water quality management is the “bridge” of pollution-free black carp farming. It is necessary to ensure that the pond water has abundant plankton and rich organic matter and nutrients; the transparency of the pond water should be maintained between 25 cm~40 cm. The dissolved oxygen content in the water should be greater than 4 mg, the pH value should be 7~8.5, and the water quality should meet the requirements of “fertile, lively, tender, and refreshing.”     II. Fry and Fingerling Cultivation     The production and introduction of black carp fry and fingerlings must comply with the provisions of China's "Fisheries Law," the "Quality Standard for Black Carp Fry and Fingerlings" (GB9956—88), and the "Measures for the Administration of Aquatic Fry and Fingerlings" promulgated by the Ministry of Agriculture. The broodstock used for reproduction must come from original and improved breed farms, and their quality must meet the standard of "Black Carp, Grass Carp, Silver Carp, and Bighead Carp Broodstock" (GB/T5055—1997). Production conditions and facilities should meet the requirements of production technical operating procedures, and the quality of fry and fingerlings must be inspected and quarantined by qualified professional technicians.     1. Selection of Fry and Fingerlings The quality of black carp fry and fingerlings can be judged by the size of the specifications when leaving the pond, body color, activity, and physical strength: high-quality black carp fry and fingerlings should conform to the "Quality Standard for Black Carp Fry and Fingerlings," with uniform specifications when leaving the pond, bright and glossy body color, lively movement, rapid diving to the bottom after being startled, and strong ability to compete for food. During sampling inspection, the fry and fingerlings jump wildly in a white porcelain basin, have plump bodies, complete fin rays, and no abnormalities. Otherwise, they are inferior fry and fingerlings.     2. Cultivation of Fry and Fingerlings According to the different feed requirements of black carp fry and fingerlings at different developmental stages, cultivation can be divided into 2 stages. (1) Fry stage. Stock newly hatched fry 3 days~5 days after hatching, at a stocking density of 1 million~1.5 million fry per hectare, with a pond area of 1334 sq m~2668 sq m being suitable. From the 1st day~10th day after entering the pond, feed soybean milk; for the first 5 days, 30 kg per hectare, and for the next 5 days, 40 kg per hectare; after 10 days, increase as appropriate, twice a day, splashing evenly over the whole pond. Every 5 days~7 days, add water 15 cm~20 cm, and by the time the summer fry leave the pond, raise the water depth to 1.3 m~1.5 m. According to the water quality of the cultivation pond, apply additional fertilizer in appropriate amounts. After about 25 days of cultivation, when the fry become summer fry, they should be thinned and divided into ponds, and before leaving the pond they should undergo two or three rounds of dense training. (2) Fingerling stage. Feeding habits gradually differentiate, and they begin to eat small snails. Stocking time is before the summer solstice, with an area of 2000 sq m~4000 sq m being suitable, a water depth of 1.5 m~2 m, black carp at 80,000~100,000 per hectare, bighead carp at 18,000~20,000 per hectare, and crucian carp at 5,000 per hectare. First use a small amount of concentrated feed to lure the black carp to the feeding platform, then feed soybean cake slurry twice a day, with 2~3 kg of soybean cake slurry per 10,000 fish each time; after reaching a size of 5 cm, mix in rapeseed cake; after 7 cm, switch to soaked rapeseed cake or soybean cake; after reaching 10 cm, mix in crushed snails and clams, starting with 30 kg per 10,000 fish and gradually increasing thereafter. Feeding should follow the “four fixed” principles. Fixed location: feed at the feeding platform or feeding ground; fixed time: twice a day, 8 a.m.~9 a.m. and 2 p.m.~3 p.m.; fixed quality: provide high-quality fresh feed according to different growth stages; fixed quantity: each feeding should be finished within 1.5 hours, and the proportion of monthly feeding amount to total feeding amount is: June 4%, July 15%, August 23%, September 25%, October 15%, November 10%, December 4%, January~March 4%. The feeding ground should be cleaned and disinfected regularly to maintain hygiene. Add water frequently, control the amount of fertilizer moderately, and keep dissolved oxygen sufficient. Patrol the pond twice a day in the morning and evening, observe carefully, arrange production according to the situation, and treat diseases promptly when found.     III. Adult Fish Farming     1. Pond Conditions The pond requires sufficient water sources and pollution-free water quality, a water depth maintained at 1.5 m~2.5 m, an area of 3335 sq m~6667 sq m, solid pond embankments that do not leak or seep water, sufficient sunlight, a flat pond bottom, and relatively little silt. Before stocking fingerlings, remove excess silt from the pond, expose it to freezing and sun for several days, add water to 30 cm, then apply 150 kg of quicklime per 667 sq m after mixing with water and splash it over the whole pond; after two or three days, inject filtered water, then use 50 kg of tea seed cake per 667 sq m, soak it for a day and night, and splash it over the pond. At the same time, power supply is required, with 1 3-kW impeller aerator and 1 feeder for every 2000 sq m~3335 sq m of water surface.     2. Fingerling Stocking Fingerlings should be stocked after the toxicity of the disinfectant has disappeared, and water should be injected through a filter to prevent wild fish from mixing into the pond. Fingerlings should preferably be stocked by around the end of February, because at this time the water temperature is lower, the fish scales are tighter, and the fingerlings are less likely to be injured during operations such as netting and transport. Per 667 sq m, stock 200~250 two-year-old black carp fingerlings weighing 1 kg each, together with 100 silver carp fingerlings weighing 0.3 kg each, 50 bighead carp fingerlings, and 20 snakehead fingerlings weighing 0.05 kg each. Before entering the pond, soak the fingerlings for 20 minutes~30 minutes in a mixture of copper sulfate (8 g per sq m) and bleaching powder (1 g per sq m), or disinfect them with 3%~5% salt water for 15 minutes.     3. Feeding Management (1) Feed selection. The feed must comply with the "Regulations on the Administration of Feed and Feed Additives," the "Safety Limit Standard for Fishery Compound Feed" (NY5072-2002), and the industry standards for aquaculture. Farming should be carried out strictly in accordance with the "Regulations on the Administration of Aquaculture Quality and Safety" promulgated by the Ministry of Agriculture, and the "Aquaculture Production Record" form should be filled in properly. The feed is required to have a uniform color, no off-odor, and no mold, deterioration, or caking; it should be granular, with a smooth surface and a high degree of cooking. The feed should not be too loose, and its water stability should be such that it does not disintegrate within 20 minutes. At the same time, the nutritional value of the feed should be evaluated. Different growth stages have different requirements for the nutritional value of feed. At the fingerling stage, feed with a protein content of 35%~45% is generally selected; at the adult fish stage, feed with a protein content of 28%~41% is generally selected.

(2) Feed feeding. Build a feeding platform extending three to four meters toward the center of the pond using wooden boards and bamboo boards, and use a taming method to make the black carp gather and float up to compete for food, gradually gathering at the feeding platform for fixed-point feeding with a feeder. The daily feeding rate can be implemented as follows: March 1.5% of fish body weight, April 2.0%, May 3.0%, June 4.5%, July 5.5%, August 6.5%, September 5.0%, October 3.0%, November 2.0%, and flexibly adjusted according to water temperature, water quality, fish growth, and feeding activity. Feed three or four times a day. Each feeding should let the fish eat until they are 70% to 80% full. Feed evenly, with the feeding duration controlled at 30 minutes~45 minutes.

(3) Daily management. Pond patrol: patrol the pond every morning and evening, check the water quality, and observe the fish conditions. Aeration: from June~September, turn on the aerator for one or two hours at noon on sunny days, turn it on in the middle of the night on cloudy and rainy days, and when floating head is severe, it must be turned on until dawn. Water quality management: regularly add new water so that the water quality meets the requirements of “fertile, lively, tender, and refreshing”; from June onward, splash quicklime over the whole pond once every 15 days~20 days (15 kg~20 kg per 667 sq m).     

IV. Disease Prevention and Treatment     The use of fishery drugs should comply with the national industry standards "Pollution-Free Food - Guidelines for the Use of Fishery Drugs" (NY5071-2002), the "Specifications for the Use of Feed Drug Additives," and the "List of Veterinary Drugs and Their Compounds Prohibited for Food Animals." Farming should be carried out strictly in accordance with the "Regulations on the Administration of Aquaculture Quality and Safety" promulgated by the Ministry of Agriculture, and the "Aquaculture Drug Use Record" form should be filled in properly.     1. Prevention of Fish Diseases In the seasons when fish diseases occur frequently, from late April to early May and from September~October, splash 90% crystalline trichlorfon over the whole pond at a dosage of 0.5 mg per liter to prevent and kill parasites such as anchorworms and Sinergasilus. Two days later, splash a chlorine-containing preparation (bleaching powder, sodium dichloroisocyanurate, trichloroisocyanuric acid, chlorine dioxide, dibromohydantoin, etc.) over the whole pond once to prevent secondary bacterial infection. From mid-May to the end of August, twice a month, alternately splash quicklime and chlorine-containing preparations over the whole pond to prevent the occurrence of bacterial diseases such as enteritis and gill rot; the quicklime concentration is 20 mg~30 mg per liter.     2. Drug Treatment Black carp fry and summer fry stages are often parasitized by parasitic fish diseases such as trichodinids and dactylogyrus; the fry-rearing stage may develop "running horse disease"; black carp fingerlings are often infected with viral hemorrhagic disease; large-size black carp fingerlings and one- to two-year-old adult fish are prone to bacterial enteritis, gill rot, and red skin disease. If fish are found to be sick, diagnose and treat them immediately.