Catla
Explanation
Composite fish culture, or polyculture, is a method of fish farming where compatible species of fish are reared together in a single pond. The selection of species is based on their feeding habits and the specific zone of the water body they inhabit, ensuring that all available food resources are utilized without competition.
Analysis of Options:
- Catla (Catla): This species is a surface feeder. It primarily consumes zooplankton and other food available in the upper layer of the water column. Therefore, it is selected to utilize the surface zone.
- Rohu (Labeo rohita): This species is a column feeder (middle zone). It feeds on filamentous algae and decaying vegetation found in the middle layer of the pond.
- Mrigal (Cirrhinus mrigala): This species is a bottom feeder. It utilizes food available at the bottom of the pond, such as decaying organic matter and detritus.
- Common Carp (Cyprinus carpio): Like Mrigal, the Common Carp is also a bottom feeder and consumes food from the pond bed.
Key Takeaway:
In composite fish culture, Catla occupies the surface zone, Rohu occupies the middle zone, and Mrigal or Common Carp occupies the bottom zone to maximize the utilization of food resources in the pond.