Composite Fish Culture and Integrated Fish Farming
Composite fish culture
Polyculture uses species that feed at different levels: catla at the surface, rohu in the column, mrigal at the bottom; exotic carps add niche coverage-grass carp for macrophytes, silver carp for phytoplankton, common carp for bottom omnivory. A common six-species mix is dominated by catla and rohu, with mrigal and the exotics making up the rest. Stocking density depends on water depth, aeration and target size; 5,000-8,000 fingerlings/ha is a typical starting range for semi-intensive ponds.
Integrated farming
Paddy-cum-fish uses shallow flooded fields with refuge trenches; rice varieties and fish must be compatible, and pesticides must be avoided. Poultry-fish or livestock-fish integration uses manure to fertilize plankton, but excessive bird density raises ammonia and oxygen demand. Integration is a nutrient-transfer system, not a way to avoid water quality management.
Worked example
A 0.2 ha pond is stocked at 6,000/ha = 1,200 fish. Use 30% catla, 30% rohu, 20% mrigal, 10% grass carp and 10% silver carp: 360, 360, 240, 120 and 120. Reasoning: percentages must sum to 100 and be applied to total number, not to each other.
Traps
- Stocking all species at the same depth niche.
- Ignoring the oxygen demand of manure.
- Using pesticides in paddy-fish fields.
- Confusing number percentages with biomass percentages.