Fish as biological control agents of golden apple snails in Philippine rice fields
2006
Halwart, M., Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome (Italy)
Common carp and Nile tilapia feed on juvenile Pomacea snails under laboratory conditions, but their effects on snail populations under actual rice field conditions were not known. The major objective of this study was to determine the impact of Cyprinus carpio and Oreochromis niloticus (stocked at 5 g individual weight) on Pomacea populations in rice fields using factorial experiments with fish species, initial snail infestation level (0.18, 0.48, and 1.32 snails/sq m), and fish density (5,000 and 10,000 fish/ha).Results showed that total snail abundance was significantly lower in the presence of common carp than with Nile tilapia at low and medium snail density. There was no significant (P0.05) effect of fish density on snail abundance. Analysis by snail size class generally showed the decreasing effect of fish species on the smaller snail size classes, with common carp being the more efficient predator than Nile tilapia. However at i ncreasing levels of initial snail infestation the abundance of snails above 4 cm shell height at harvest increased where common carp were present. It is concluded that fish can play an important role in snail management, and a density of 5,000 fish/m is considered adequate for overall snail control at an infestation level of 0.5 snails/sq m. The most promising option of using for sustainable snail biocontrol appears to be the stocking of fewer but larger fish in combination with other control measures that particularly aim at reducing the larger snails.
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