Growth, production and food preference of rohu Labeo rohita (H.) in monoculture and in polyculture with common carp Cyprinus carpio (L.) under fed and non-fed ponds

An experiment was carried out in 18 earthen ponds to investigate the effects of the addition of common carp Cyprinus carpio (L.) and artificial feed on natural food availability, food utilization and fish production in rohu Labeo rohita (Hamilton) ponds. Ponds were fertilized fortnightly with cow manure, urea and triple super phosphate. Rohu was stocked in all ponds at a density of 1.5 rohu m−2. All treatments were carried out in triplicate. Treatments were: rohu with and without formulated feed, rohu plus 0.5 common carp m−2 with and without feed, and rohu plus 1 common carp m−2 with and without feed. The time period between stocking and harvesting was four and half months. Stocking 0.5 common carp m−2 enhanced natural food availability in the pond, food utilization and rohu growth and production (P0.05) but increased zooplankton and benthic macroinvertebrate availability (P