At first glance, the lush, jade-green rice fields in South Sumatra seem like those of any other in Southeast Asia. But a closer look reveals fish popping and lashing about in the wet fields. Rice-fish farming is a farming method by which a flooded rice field, or paddy, is used for raising both rice and fish.
To begin a rice-fish operation, the farmer digs a small pond or trench about 0.5-1 metre deep in a low-lying area of the rice field, to function as a deeper water 'refuge' for the fish. The excavated soil is used to raise the banks of the field to allow water control and to create a raised area above flood level, which is suitable for planting other crops like vegetables and fruit trees.
The rice fields are then flooded to form shallow bodies of water in which warm-water fish such as the common carp can live. The fish, in search of food, loosen the soil and eat the seeds of weed plants and the larvae of the rice midge. Their excrement fertilises the soil.
The presence of fish results in an increase in rice yield. When the fish are fed and the fields are fertilised, fish productivity increases per hectare of water.