Raising ducks on fish ponds on a small scale is an old practice in Europe and Asia, especially in China, but the interrelationships between ducks and fish and the commercial possibilities of such systems have only recently been evaluated. The first scientific experiments on duck-fish farming were made by Probst in Germany in 1934, but because of World War II, the results remained un-utilized. After the World war II, due to serious protein shortage in European countries, large-scale experiments were iniciated in Hungary (1952), Czechoslovakia (1953) and East Germany (1955) to determine optimal husbandry methods for raising ducks on fish ponds. The raising of ducks on fish ponds fits very well with the ecological niche concept of polyculture. In conventional polyculture, the major niches are all occupied by various species of fish, except for the water surface niche which is un-utilized. The ducks consume such organisms as tadpoles, mosquitoes, larvae of dragon flies and other insects, molluscs and aquatic weeds and thus do not compete significantly with the fish for any food items commonly found in conventional polyculture of carps. Duck manure fertilizes the pond and their disturbance of the substrate while feeding, helps to release nutrients from the soil and further increases fish production.
The results and experience obtained at Barrackpore Research Institute, India, suggest that 100 to 150 ducks can give adequate fertilization to 1 ha of water. This is comparable with the recommendation of Behrendt (1978): i.e. 300/ha average and 100/ha where natural food is limited. In the present experiment, 100 ducks provided approximately 10,000 kg of manure over 12 months. Ducks are likely to eat small fish and should be excluded from nursery ponds. Fingerlings of 10 cm or over are recommended for stocking in Duck-fish systems (Jhingran and Sharma, (1978).
Integrated livestock - fish farming not only increases fish production but also cuts down the cost of fish culture operations considerably. The average cost of production in conventional polyculture with supplemental feeding and inorganic fertilization was Rs. 2.93/kg in Eastern India (Anon, 1976). Murshed et al. (1977) have also recorded Rs. 2.67/kg as the cost of fish production by conventional methods in Nadia, district, West Bengal. Jhingran and Sharma (1978) have recorded the cost of production as Rs. 1.07/kg (Pig-fish) and Rs. 1.61/kg (duck-fish farming). Woynarovich (1979) reported that in Taiwan, duck-fish operations produce an average of 3,500 kg/ha/year of fish. Polyculture, selective harvesting and stocking, and high density of ducks ranging from 1,000 to 1,500/ha are practised. The fish yields from similar operations in Hong Kong are higher ranging from 2,750 to 5,640 kg/ha/year with about 2,000 to 2,400 ducks/ha.
Based on an estimated manure output/duck of 6 kg/40 day or 150 g/day (Woynarovich (1979), the level of duck-manure application in Taiwan is 150 to 225 kg/ha/day. In Hong Kong it is 300 to 360 kg/ha/day.
Information available from Allen and Hepher (1979) FAO (1977b), Moav et al. (1977) and Rappaport and Sarig (1978) shows that ponds receiving from less than 0.5 to more than 1.0 t/ha/day can give fish yields from 1,500 kg to more than 8,000 kg/ha/year according to local conditions.
Experiments conducted in the German Democratic Republic on duck-fish farming showed an average increase in carp production of 100 kg/hectare with 300 ducks/ha kept on the ponds. In Hungary, 300 to 500 ducks/ha give fish yields of 500 to 800 kg/ha in 150 days, (Woynarovich, 1979).
In Hong Kong, about 58% integrated fish farms raise ducks and about 8% raise geese. The number of ducks ranges from 2,500 to 3,500/ha/year to yield 5–6 t/ha of duck meat and 2,750 to 5,640 kg/ha of fish (Sin and Cheng, 1976). Table (7)given below shows economics of polyculture and duck fish system.
| Large farms (over 4 ha) (unit/ha) | Medium farms (1.5 to 4.0 ha) (unit/ha) | Small farms (below 1.5 ha) (unit/ha) | |||||
| with ducks | without ducks | with ducks | without ducks | with ducks | without ducks | ||
| Area (ha) | 5.32 | 6.80 | 2.20 | 2.80 | 1.50 | 1.53 | |
| Number of ducks/ha/yr | 2,409 | - | 1,971 | - | 2,117 | - | |
| Duck yield: | Quantity (kg) | 6,071 | - | 5,002 | - | 5,354 | - |
| Value (HK$) | 36,720 | - | 29,508 | - | 33,777 | - | |
| Duck feeds: | Quantity (kg) | 27,320 | - | 23,509 | - | 26,235 | - |
| Cost (HK$) | 28,080 | - | 23,143 | - | 26,250 | - | |
| Feed conversion ratio (duck) | 4.5 | - | 4.7 | - | 4.9 | - | |
| Fish yield: | Quantity (kg) | 5,640 | 5,865 | 3,968 | 4,050 | 2,750 | 3,000 |
| Value (HK$) | 41,767 | 47,783 | 34,038 | 34,435 | 22,697 | 25,195 | |
| Fish feeds: | Quantity (kg) | 15,038 | 19,143 | 10,753 | 14,175 | 7,893 | 9,300 |
| Cost (HK$) | 11,278 | 15,893 | 7,209 | 10,208 | 5,523 | 7,068 | |
| Feed conversion ratio (fish) | 2.67 | 3.26 | 2.71 | 3.50 | 2.87 | 3.00 | |
| Feed cost/kg fish produced (HK$) | 2.00 | 2.71 | 1.82 | 2.52 | 2.01 | 2.36 | |
| Net income: | Fish | 15,892 | 18,155 | 13,461 | 9,117 | 5,156 | 5,644 |
| Duck | 2,352 | - | 1,965 | - | 2,025 | - | |
| Total | 18,244 | 18,155 | 15,426 | 9,117 | 7,181 | 5,544 | |
| Input-output: Ratio of net income/total costs | 0.61 | 0.61 | 0.65 | 0.36 | 0.29 | 0.28 | |
| Fish operation: Ratio of net income/running costs | 0.69 | 0.69 | 0.73 | 0.39 | 0.34 | 0.32 | |
Source: Sin and Cheng, 1976.
In Vietnam, raising 1,000 to 2,000 ducks/ha on ponds increased the average fish yield to 5.0 tonne/ha/year compared to 1.0 tonne/ha/year without ducks. (Pullin and Shehadeh, 1980).
Duck-fish farming is still at an experimental stage in India. Demonstration trials have yielded 4,323 kg/ha/year with 100 to 150 ducks/ha (Sharma et al. 1979). Nepal has also introduced duck - fish farming with assistance from the Food and Agriculture Organization of the United Nations (FAO) and United Nations Development Programme (UNDP) and initial production estimates of 1.0 to 1.5 kg/ha/year are considered feasible (Woynarovich, 1979).
Aquaculture in enclosures was introduced in Laguna de Bay lake (in Philippines) in 1971 and gave yields of 4 tonne/ha/year (Delmendo and Gedney 1974), making full use of the high productivity of the water.
There appears to be no significant difference in the taste and texture of flesh of fish grown in manured ponds and those fed commercial diets. Allen and Hapher (1979) report that fish from ponds receiving well-treated domestic wastes taste as good or even better than fish grown in waste-free ponds. Similarly, Moav et al., (1977) report good flesh colour and intramuscular fat-levels for fish grown in intensively manured ponds.
Sobol (Pers. Comm. Research Station, Dor, Israel) analysed the fat content of approximately 100 carps grown on manure, grains and on fish meal-enriched pellets. The fat concentrations were 6%, 20% and 15% respectively. The taste-quality of the manure grown fish was considered superior.
The aspect of off-flavor fresh water fish growing under various water qualities and nutritions was reported by Meyers (1975) with particular respect to consumer acceptance and a standard allowing the identification of the producer with other than conventional individual characteristics such as flavor, taste and appearance. The authors conclusions were as follows: if a ration formula such as the OMP (oregon moist pellet) is necessary for feeding bass artificial diets, it should be replaced perhaps with forage fish, a few days or weeks before the fish is to be consumed. The organoleptic quality of aquaculture crops is of no small significance and may pose serious problems in consumer acceptance. Attention must be given to maintenance of product quality to establish that the consumer receives products with identifiable characteristics of flavor, taste and appearance.
