Growth

Mandarin fish has a rapid growth rate, but growth is highly related to food sufficiency, temperature and stocking density. The fish can reach 50–100 g during the first year following hatching (in May to December), a weight of 500 g in the second year and 1–1.5 kg in the third year. However, the growth rate declines after the fourth year. In ponds under controlled conditions that practice intensive feeding, mandarin fish can reach 400–600 g in the first year (i.e. in 100–120 d) and 1–1.5 kg in the second year. The growth rates for both body weight and length decline thereafter. Males grow faster than females in the first year, while in the second and the third years females grow faster than males.

Growth rate has also been observed in cage culture in open waters. Practical performance showed superior growth as compared to that seen in pond culture. A trial was prepared with two types of cages, type 1 being a cage of 4 x 3 x 3 m with mesh size of 1 cm and type 2 being a cage of the same size having a mesh size of 1.5 cm. The initial size of the fish stocked was between 10–13 cm in body length, and the stocking density was 40 fish/m². At six weeks, the fish were transferred to the grade-2 cages at a density of 18 fish/m², where they were raised until week 28. In the first phase of six weeks, fish body length increased from 11.5 to 19.0 cm and body weight increased from 50 to 81.4 g. (i.e. the length doubled and the weight increased by 1.5 times). However, as the fish were reared to week 28, the body length only increased by 50 percent, while the body weight gained by a factor of 6. The growth performance reported by Cui et al (2000) is shown in Table 5. During the total farming period of 28 weeks, the total feed quantity was 1 683 kg of trash fish, the total weight of all fish reached 207 kg with a survival rate of 88 percent, 90 percent of the fish reaching marketable size. These 207 kg had a value of 8 713 yuan (RMB), the net profit gained (after deducting operating costs, feed costs and depreciation) was 5 292 yuan, giving a cost/benefit ratio of 1:1.5.