FAO Polyculture - Fish
One way to intensify fish culture without an input of expensive feed is through polyculture. In this way the natural food produced in the culture environment is utilized to a greater extent through compatible or complementary feeding habits of fish which do not compete with each other. In order to utilize natural food to its maximum, and as fish may change their food if their regular food resources become exhausted, it is very important to ascertain the correct ratio between the different species in the polyculture according to the ecological conditions in the pond and to adjust them so that they do not compete with each other.
Yields obtained by polyculture are usually much higher than those obtained by monoculture, especially if the right species have been chosen. Other benefits also may be gained by polyculture, as, for example, quite often the ecological conditions in a pond are improved by polyculture. It has been found that Tilapiaaurea in a polyculture system improves the oxygen balance by feeding on the detritus which would otherwise decompose and take up oxygen. Silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) also improve the oxygen balance by feeding on excess plankton. These fish may also gain by feeding on the excreta of common carp (Cyprinus carpio) or other fish.
The major drawback of polyculture is its complexity.