Composite Fish Culture, Stocking Density and Polyculture Systems
This domain tests species combinations, vertical feeding niches and stocking calculations. The core idea is that compatible species use different pond layers and food, so total yield rises without crowding one niche.
Core rules
- Indian major carp polyculture commonly combines catla (surface), rohu (mid-water) and mrigal (bottom).
- Composite fish culture adds exotic carps: silver carp (surface plankton feeder), grass carp (macrophyte feeder) and common carp (bottom omnivore).
- Stock healthy fingerlings of similar size; stock in the cool part of the day and acclimatize temperature.
- Stocking density is total fingerlings per hectare, not per species. A common range for composite carp culture is roughly 5,000–10,000 fingerlings/ha, adjusted for water depth, aeration and management.
- Use a species ratio that matches food supply; excessive grass carp can destroy aquatic plants, and too many bottom feeders can compete.
Worked example
A 1-ha pond is stocked at 6,000 fingerlings/ha with catla:rohu:mrigal = 4:3:3. Total ratio parts = 10. Catla = 6,000 × 4/10 = 2,400; rohu = 6,000 × 3/10 = 1,800; mrigal = 1,800. Reasoning: first find the total, then multiply by each share. Do not apply 6,000 to each species.
Traps
Do not add species without checking niche overlap. Do not treat the ratio as a percentage of pond area. Do not stock all-male or all-same-size groups without considering competition. Do not count total density as 6,000 of each species.