Rice/Fish Farming in Malaysia, Improving a Time-Tested Technique
Malaysians have been practicing low-input rice/fish farming for over 1,500 years. Fish provide more than 50% of the animal protein consumed in Malaysia, as well as an important seasonal supplement to the income from rice harvests, as much as 9% of the farmers' income. As sea fish resources are depleted and fuel costs rise, inland aquaculture systems are becoming increasingly important. However, fish productivity has decreased in these inland systems since the 1970s, as government-mandated double cropping of rice has shortened the growing season, followed by the increased use of pesticides.
The North Kerian irrigation area in Perak state is one of the major fish production areas in Malaysia. Ironically, productivity and efficiency are the lowest in this area despite the fact that it exports both fresh and dried fish to countries such as Singapore and Thailand.
Ahyaudin B. Ali of the Malaysia University of Science conducted a study on the rice/fish farming systems in the North Kerian area to describe the system and obtain basic ecological data. The study covered three growing seasons: from September to December 1985 (season 1); February to May 1986 (season 2); and September 1986 to January 1987 (season 3).
Rice plots that were studied averaged 1 ha, with sump ponds about 6.5 to 8 m in diameter and 2 m deep. Farmers prepared the fields by using a paraquat-based herbicide (Gramoxone) to control weeds and removing the dead weeds by hand. Two to four weeks after transplanting rice seedlings, they applied chemical urea and NPK at a rate of 56 and 112 kg/ha, respectively. They also applied Furadan, now a restricted use pesticide in the U.S., at a rate of 5.6 kg/ha along with the fertilizers.
Wild fish enter the flooded rice fields at the beginning of each season, where farmers retain, grow and harvest them. The system requires minimal inputs and is both cost- and ecologically efficient. Farmers provide no supplemental feed for the fish, but rely on the productivity of their rice fields to feed them. Several indigenous fish species are well-adapted to the system, each occupying a specific ecological niche. They have different feeding habits and physiological adaptations that complement each other.
Of the seven dominant native species found in North Kerian, the most profitable is live catfish (Clarias macrocephalus), followed by live snakehead (Channa striata), and then snakeskin gouramies (Trichogaster pectoralis).
At the end of the rice-growing season, when the fields are dry, fish take refuge in the canals and sump-ponds. Farmers harvest some of these fish immediately, some during the dry season, and some remain to stock the rice-fields in subsequent seasons.
The average amount of fish of all kinds harvested during the study period ranged from 88.3 kg/ha in season 1, to 128 and 174.6 kg/ha in seasons 2 and 3.
Fish yields in the Kerian are low because of the low natural productivity of the system. Despite seasonal fertilization of the rice crops, data suggest that nutrient availability in the water remained low, as did phytoplankton productivity and zooplankton production levels. The low phytoplankton production may be due more to shading and plant competition than to the low nutrient levels. Many fast-growing weeds, dominated by Salvinia molesta, Bacopa monnieri, and Hydrilla verticillata, can colonize the water column by mid-season. Zooplankton are crucial for larval and juvenile fish growth and their low levels may explain the preponderance of small fish at harvest.
Recommendations focus on increasing productivity:
Management should focus on cultivating rather than capturing fish.
Higher dikes would prevent fish from escaping.
Perimeter trenches should be dug to provide additional refuges for fish, and for plankton production.
Liming and applying organic matter should decrease soil acidity and improve the plankton environment.
Herbicides should be used sparingly. Less toxic pesticides should be used.
Weeds should be cleared early in the cycle to allow fish larvae and juveniles to feed on plankton .
In addition to low productivity, the short growing-season resulting from double-cropping rice also affects fish yields.
Since returning to a longer single-cropping system is not a legal option, stocking with fingerlings and providing supplementary feed could result in larger quantities of marketable fish in the shorter season. Farmers have practiced these methods for centuries at no cost, for this reason a cost-benefit analysis should be done before any of these recommendations are implemented. Such a study is being carried out in Kerian .
New practices to further integrate aquaculture and agriculture in Kerian include planting fruit trees on the dikes surrounding the sump ponds. Farmers also plant the perimeter dikes with tapioca, squash and sweet potato. Others have begun feeding the snakeskin gouramy rice bran. These are recent innovations and their economic feasibility has yet to be determined, but they indicate a large untapped potential for improving productivity.
Ahyaudin B. Ali, Rice/Fish Farming in Malaysia: A Resource Optimization, Ambio Vol. 19 NO. 8, Dec. 1990.
Ali B. Ahyaudin
School of Biological Sciences
University of Science Malaysia