Since silver carp is filtering fish, fertilizer is the main method for producing natural food. Silver carp are normally reared in integrated, manure based, polyculture systems with other Chinese major carps and / or common carp. Chemical fertilizers can be used instead of animal manure. In general, 25 kg animal manure or 50 kg green manure is required to produce 1 kg of filter feeding fish. The application of 110 000 kg of animal manure or 2 250 000 kg of grass as green manure per annum is required to obtain a yield of 4 500 kg of fish/ha. Monthly rate of fertilizers vary on a seasonal basis. During the summer months almost twice as much fertilizer is applied as during the winter months (Zhan and Yang, 2002). Animal manure should preferably be fermented before use. Ammonium chloride has been found to be more efficient as a fertilizer than ammonium bicarbonate and urea (Pan et al., 1994).

The stocking density is around 1 200 000–1 800 000 individuals/ha (Aquaculture Department, Chinese Ministry of Agridulture, 1993). There are generally several ways including green manure, soybean slurry, organic fertilizer and inorganic fertilizer etc. (Table 4) (Cai, 1987).

Stocking density for fingerlings is around 210 000–225 000 individuals/ha (for whole period) or 750 000–1 200 000 individuals/ha (for two periods stocking, distributed during second period) or 2 250 000–3 000 000 individuals/ha (for three periods stocking, distributed during second and third period) and is normally composed of 70 percent silver carp, 15 percent grass carp, 5 percent bighead carp and 10 percent common carp. After stocking, the pond should be fertilized once every seven–ten days with 1 500 kg grass manure and 1.5–2 kg soybean (in slurry)/10 000 fingerlings (increase to 2.5–4 kg when fish getting bigger) (Cai, 1987).

The stocking density for Age I juveniles is depended on the harvest size and normally around 225 000–300 000 individuals/ha. The harvest size is around 8.3–9.9 cm. Age II: Age I juveniles could be stocked at 15 000 individuals/ha. Basal fertilizers is allocated at 750–1 500 kg animal manure/ha or 3 000–4 500 kg grass manure/ha 7–10 days before stocking After stocking, 1 500–4 500 kg/ha grass manure or animal manure is allocated once every 10–15 days during first month and once every 15 days during second month. During the second month, about 2–3 kg seed cake should be allocated per 10 000 individuals per day.

The stocking density for silver carp is around 75 000–120 000/ha. Basal fertilizer 5 days before stocking should be 3 000–37 500 kg grass manure and 5 250–6 000 kg/ha and the annual fertilizer should be around 110 000 kg animal manure or 2 250 000 kg grass manure for producing 4 500 kg fish (Cai, 1987; Zhan and Yang, 2002).

Silver carp broodstock ponds are best prepared by the application of 4 500–7 500 kg animal manure/ha followed by 10–13 tonnes/ha per month according to water colour. If inorganic fertilizers are used then 15–22 kg urea and calcium superphosphate are applied / ha /month (Zhan and Yang, 2002). Prior to the onset of winter the ponds are normally fertilized with 3 000 kg animal manure/ha to improve fish health and in spring the broodstock ponds should be fertilized every two or three days to promote plankton growth.

Under polyculture conditions silver carp is often used to optimize the use of nutrients provided by pellets used to feed other species (e.g. common carp) and also benefit from the nutrients added to the water by faeces from other species (Hu et al., 1997).

Net fish yield (FYn, kg/ha/year) of silver carp is depended on gross photosynthesis (PGv, mg O₂/L/day) and is described by Log10FYn=0.047PGv+2.44 (n=18, r2=0.76, P<0.001) (Liang et al., 1981).

Huang and Hu (1991) attempted to predict filter feeding fish production on the basis of detritus and plankton carbon cycling and Wang and Liang (1995a,b) compared different models to evaluate filter feeding fish production capacity. Results so far have been inconclusive. Food conversion ratios for phytoplankton and zooplankton by filter feeding fishes have been calculated at 40 and 10:1, respectively (Wang and Wang, 1994).