Experience sharing on self-breeding live bait for mandarin fish farming

Last year, the mandarin fish farming area in Wujiang City exceeded 10,000 mu. Zhang Qifang, a skilled mandarin fish farmer at the Sixth Branch of the East Taihu Aquaculture General Farm, farmed 20 mu of mandarin fish in 1999, with 83.5 mu of supporting ponds (of which 44 mu were used for restocking oriental river prawns), achieving a mandarin fish yield of 613 kg per mu and a per-mu profit of 3,163 yuan; the per-mu profit from mandarin fish alone exceeded 10,000 yuan. In 2000, he farmed 17 mu of mandarin fish, with a yield of over 700 kg per mu and an average per-mu profit of over 3,500 yuan.

Pond conditions: each pond is 7-10 mu, with a water depth of 1.5 m, clean water quality, and the ponds are sun-dried for half a month before fry stocking, with relatively hard bottoms. 7-10 days before stocking, 50 kg of quicklime per mu is used for dry pond disinfection.

Fry rearing and separation

In early May last year, 35,000 mandarin fish summer fry of 2-2.5 cm were purchased and placed in a 5.6-mu pond for fry rearing, with an average stocking density of 6,250 fry per mu. Before the mandarin fish summer fry were stocked, sufficient suitable forage fish were cultivated in the fry pond. In early June, 31,500 mandarin fish of about 7 cm were harvested from the pond, with a survival rate of 90%. Of these, 22,300 were placed in a 17-mu pond for grow-out (1,310 per mu), and 9,200 were sold. A total of 6 million forage fish were consumed (including fry, summer fry, fingerlings, etc.).

Feeding forage fish

Forage fish were reared in supporting ponds, generally at a size one-third of the mandarin fish body length. Forage fish were fed once every 3-4 days. During the high-temperature period from August to early September, the amount of forage fish fed was controlled to slow the growth rate of mandarin fish and reduce disease occurrence. Throughout the entire farming period, a total of 46,700 kg of forage fish were consumed (of which 38,000 kg were self-bred), with a feed coefficient of 3.9.

Water quality management

Clean water quality is required, with a pH of 7-7.5, a transparency of 35-40 cm, and sufficient dissolved oxygen. Every half month, 30 cm of water is added. Before adding water, the external river water is first pumped into a storage pond. After being biologically purified by aquatic plants and plankton in the storage pond for 5-7 days, it is then pumped into the mandarin fish pond. At the same time, bactericidal drugs and insecticidal drugs are each applied once to the mandarin fish pond. Each pond is equipped with 2 units of 3-kW aerators and 1 unit of 8-inch water pump. From mid-July to mid-September, the equipment is operated as appropriate according to the feeding and activity of the mandarin fish and weather conditions, generally 6-8 hours per day.

Fish disease prevention and control.

(1) Forage fish must not have water pumped into their pond within half a month before netting, and before being placed into the mandarin fish pond, they are bathed in 5 mg/L potassium permanganate for 15 kg.

(2) During fry rearing, when mandarin fish are 2.5-5 cm, the focus is on preventing and controlling parasites (Trichodina, Chilodonella); when above 5 cm, the focus is on preventing and controlling bacterial diseases.

(3) From June to mid-September, drugs are used regularly for disease prevention. First, Baidujing (or strong chlorine, Wanxiaoling, etc.) is used for water disinfection, and the next day, copper sulfate plus Yushuangling (or Diyuchong) is used to kill parasites. This is done once every 7 days.