Evaluation of different species of fish for biological control of golden apple snail Pomacea canaliculata (Lamarck) in rice

The concept of rice-fish farming was employed to evaluate five species of fish for biological control of golden apple snail in rice. Aquaria trials were initially used to observe the predation potential of the individual fish species, followed by replicated field trials. In the aquaria studies all the fish species preyed upon the hatchlings of the golden apple snail, but at the field level only common carp and African catfish consumed snails significantly more than the other species. Common carp, which attained a recovery rate of 90% was the only fish species suitable for biological control of snail in rice. African catfish was not adaptable to the rice field conditions; the fish suffered a low recovery rate of 17% even when the plots were covered with nets to protect the fish from natural predators. The density of common carp recommended for biological control of snail in rice was 2041 fish/ha. However, it was essential to set up a pond refuge to improve survival rate and to enhance fish production. The study revealed that under direct seeding planting method, the increase in plant density restricted the foraging activities of the fish. Consequently, the number of snail sampled in direct seeded plots was significantly greater than in transplanted plots. Throughout the studies, the fish neither caused a significant increase in rice yields nor a reduction in stem borer, case worm and stink bug infestations. Common carp was however, an effective predator of the golden apple snail in rice. (c) 2006 Elsevier Ltd. All rights reserved.