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The combination of rice and fish production into one system is considered to be an efficient means of agricultural land use for small-scale farmers. In some of these so-called rice-fish systems rice and fish are grown in the same field, at the same time; in other systems they are grown in the same field, but in rotation. Rice-fish farmers pay most attention to the maximization of the rice yield. This is a logical choice because the rice field is not the most ideal environment for fish production as the rice crop shades the field floodwater, thus hampering aquatic primary production. Still, practically all-major freshwater species being farmed, worldwide, have been successfully raised in rice field ecosystems. Farmers usually opt to stock several fish species in a polyculture in an attempt to make optimal use of all ecological niches in the rice field. Fish yields are usually low but can be substantially increased when additional feed or manure is added to the system. One of the advantages of rice-fish culture is that it gives farmers new and sustainable opportunities to apply integrated pest management (IPM). Indeed, the presence of fish in the rice fields shifts the economic threshold for pesticide applications to a level which is unlikely to be reached by pest populations. Fish are also known to control weeds in rice fields. The rice yields in rice-fish systems are sometimes higher, and sometimes lower, when compared with those from rice monoculture systems. The mechanisms for this are not always well understood. The increase in household income might be substantial, but the high input costs associated with the system often deter farmers from adopting it. Nevertheless, rice-fish farming can provide a sustainable alternative to rice monoculture, both from an economic as well as an ecological point of view.
