6th Grade - Science

LESSON PROBLEM: Biology: How is combining fish farming and rice farming beneficial?


Raising rice and fish in fields together is a practice of natural symbiosis. Catching fish in rice fields that had found their own way into flooded fields gave farmers the idea of purposefully introducing fish into their rice fields. In Asia and other developing countries, this practice has evolved and expanded resulting in ecological, financial and social benefits.

Rice fields are complete ecosystems supporting a food chain. Through the mechanics of this ecosystem soil is fertilized, the need for pesticides is reduced through natural weed and insect control and human health is improved.

Through rice-fish farming, a natural, balanced way of farming has emerged. Manure is the main fertilizer used in rice-fish farming. With manure in a rice field, plankton reproduce rapidly and offer a food source for the fish. Fish in rice fields also decrease the amount of mosquito larvae, which reduces the number of malaria cases. Malaria is an infectious disease transferred to people by mosquitoes. Before, insecticides were used to control mosquitoes, but after a while those had no effect on the insecticide resistant strains that developed. Fish effectively control mosquitoes.

Because fish feed on insects, insect problems are lower in rice fields that contain fish. One example of how fish solved a near devastating problem is in the infestation of many Asian rice paddies by the Latin American Golden Apple Snail. The problem with this snail arose 20 years ago, but recently it has been found that the common carp is effective in reducing the snail population by as much as 90 percent. They are particularly effective with younger snails, as they have smaller shells. The fish are the snails' natural predators. It is up to the rice farmers to exploit this predator relationship to benefit their rice fields. Many methods were tried with the aim of controlling the snails, but most often the farmers ended up having to replant the rice plants.

The Food and Agriculture Organization of the United Nations had a large role in reaching out to farmers in countries like Vietnam and the Philippines, making them aware of the seriousness of the Golden Apple snail problem. Then training them on how to use fish farming to control these pests.

Fish also control weeds. Some feed on weed roots and offer an extra service by tilling the soil around the rice plants. Fish-rice fields are constantly being weeded in this manner. The fish's activity in the field helps mix the manure and soil. Fish also excrete manure that is high in nutrients which the plants use.

Because the water in rice fields is shallow and replenished frequently, it is fresh and contains low levels of bacteria. This reduces the occurrence of fish diseases. Rice fields are actually healthier habitats for fish to live in than many common fish ponds.

Rice-fish farming is dually beneficial because it also supplements the farmer's diet and creates another profitable crop. Fine, market-size fish are produced which can greatly increase the farmer's income, sometimes doubling it.


List four advantages to raising fish in a rice field.

What would you say to a rice farmer to convince him that it is a good idea to have fish live among his rice plants?


What other animals that live in rice fields can be beneficial in weeding and ridding the field of pests? What can a farmer do to introduce or attract these other animals to his field?


  • pest
  • predator
  • pesticide
  • symbiosis

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Baldo is actually a type of specialty rice grown right here in the U.S. Other types include basmati, jasmine and arborio.
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