What are the key technical points for farming freshwater pomfret (piaractus brachypomus)?

Freshwater pomfret (piaractus brachypomus) has the characteristics of good meat quality, large body size, fast growth, broad feeding habits, few diseases, tolerance to low oxygen, and easy harvesting. It is a valuable large-sized commercial fish, and its introduction and promotion play a positive role in improving economic returns, improving farming structures, and enriching the food supply.

Biological Characteristics of Freshwater Pomfret

1. Morphological characteristics: The body of the freshwater pomfret resembles that of a marine pomfret, oval-shaped, laterally compressed, with a small head, head length roughly equal to head height, a forked tail with the lower lobe slightly longer than the upper lobe, an adipose fin on the back, cycloid scales covering the body, saw-like ventral scutes from the base of the pectoral fin to the anus, a silver-gray body color, red pectoral, pelvic and anal fins, and a black-edged caudal fin. When young, the freshwater pomfret has black spots on the body surface, which disappear in the adult stage. Adults stocked in ponds display a striking combination of four colors: white body, silver scales, black tail, and red fins, making them very beautiful, hence they are also a good ornamental fish. According to reports, in its place of origin this fish can reach a maximum individual weight of 20 kg.

2. Living habits and feeding habits: Freshwater pomfret lives in the middle and lower layers of water bodies, likes to gather in groups and swim in schools, and individuals within the group do not kill each other. The freshwater pomfret has a well-developed digestive system and is an omnivorous fish, feeding both on animal food such as small fish, shrimp and benthic animals, and on plant food such as small grasses, vegetables and algae. Under artificial rearing conditions, it can be fed wheat bran, rice bran, soybean cake and compound feed.

3. Ecological habits

① Suitable temperature range: The growth temperature for freshwater pomfret is 21—32℃, the optimum temperature is 28—30℃, and the lowest critical temperature is 10℃. The normal feeding temperature is 16℃. In the middle and lower reaches of the Yangtze River and the Huaibei region, it enters a dormant state below 14℃, lying on its side on the pond bottom.

② Oxygen tolerance: Freshwater pomfret has a relatively strong tolerance to low oxygen; it can survive for several hours at a dissolved oxygen level of 0.5 mg/L, and the optimal dissolved oxygen for its growth is 4—6 mg/L.

③ Salt tolerance: It can grow normally in water with a salinity of 5—10‰, with no fish diseases, and dies within 16 hours at a salinity of 15‰.

④ pH adaptation range: pH 5.5—7.4, preferring slightly acidic or neutral water.

⑤ Catch rate: The freshwater pomfret is docile and fond of gathering in groups; generally the first net catches more than 90%, and two nettings can basically catch them all.

⑥ Tolerance to commonly used drugs: The freshwater pomfret is most sensitive to organophosphorus pesticides and trichlorfon; at 0.2 ppm it dies after 11 hours, at 0.5 ppm mass mortality occurs in only 3—4 hours, and at 1 ppm it dies immediately. At a water temperature of 20—25, 0.3 ppm malachite green will also poison freshwater pomfret. 0.135 ppm will cause "red head" symptoms. Soaking the fish in 10 ppm copper sulfate for 25 minutes causes no abnormal phenomena; bleaching powder (30% effective chlorine) at 2 ppm causes no abnormality, but at 4 ppm the fish lose balance after 20 minutes and die within 100 minutes. Mercurous nitrate at 0.2 ppm causes no abnormality, at 1 ppm all die within 10 hours, and 0.1 ppm has a special effect on preventing and treating ichthyophthiriasis.

Grow-out Farming of Freshwater Pomfret

1. Main stocking of overwintered fingerlings: Overwintered fingerlings generally weigh 15—20 g. In the middle and lower reaches of the Yangtze River and the Huaibei region, stocking generally begins in early to mid-May and harvesting takes place in mid to late October; the growth period is 5 months, and the average body weight reaches more than 750 g.

2. Polyculture of overwintered fingerlings in grow-out ponds: When polyculturing freshwater pomfret overwintered fingerlings in high-yield grow-out ponds, the size should be somewhat larger, preferably 40—50 g, with 50—60 fish per mu, without increasing feeding, which can increase production by 50—60 kg.

3. Cage farming: The freshwater pomfret has dense scales, is not suitable for injury, has strong disease resistance, likes to gather in groups, and readily eats artificial compound feed, so it is suitable for cage farming.

① Cage requirements: The freshwater pomfret has sharp teeth on the upper and lower jaws; to prevent it from biting through the cage, a single-layer steel wire mesh structure is generally used. The specifications are 4×4×2 or 4×6×2 cages, with a mesh size of 3 cm, mostly without a cover net. When setting up the cage, the top should be 0.5 m above the water surface.

② Fingerling stocking: Overwintered fingerlings are put into the cage in mid-May, preferably at a size of 15 g—20 g per fish, with a monoculture density of generally 150 fish per square meter.

③ Feed requirements: Artificial compound feed with a protein content of 25—28%.

④ Feeding method: Start training the fish to feed two days after they enter the cage, with small amounts and many times. When the water temperature is above 25℃, feed four times a day. Be patient when feeding, scatter while observing, until most of the fish are full and swim away. The three months of June, July and August are the best growth period, so the protein content should be increased and the feeding amount enlarged.

⑤ Daily management: Daily management should achieve the "three preventions": disease prevention, escape prevention, and theft prevention. The water body where the cages are set up must be pollution-free, disease-free, and the water quality must be fresh. When the fingerlings enter the cage, soak them in 3—5% salt water for 15—20 minutes; after they enter the cage, hang bleaching powder baskets; clean and inspect the cages regularly to prevent fish escape due to damage; assign personnel to watch over them and keep daily records.