Name the six species of fish cultivated in composite fish culture systems.

Composite fish culture systems in India typically cultivate six compatible species that occupy different feeding zones of a pond: Catla (surface feeder), Rohu (middle zone feeder), Mrigal (bottom feeder), Grass Carp (vegetation feeder), Silver Carp (plankton feeder in upper water layers), and Common Carp (bottom feeder consuming detritus and decaying matter). This combination maximizes productivity by utilizing all ecological niches within the pond ecosystem without competition for food resources.

The selection of these six species represents decades of aquaculture research demonstrating how different feeding habits can be leveraged in a single water body. Catla feeds on zooplankton near the surface, while Rohu consumes phytoplankton and decaying vegetation in mid-water. Mrigal and Common Carp scavenge the bottom layers for different food types, while Grass Carp controls aquatic weeds and Silver Carp filters phytoplankton. This polyculture approach yields 3-5 times more fish per hectare compared to monoculture systems, making it economically superior for small-scale farmers.