Common carp Cyprinus carpio (L.) and Nile tilapia Oreochromis niloticus (L.) were evaluated in
the Philippines in replicated field plot trials as biocontrol agents of the golden apple snail (GAS)
Pomacea canaliculata (Lamarck) in rice-fish culture. Carp are more adapted to consume snails
than tilapia by possessing pharyngeal jaws and they frequent the benthos where more GAS
reside. GAS densities at rice harvest were lowest in paddies stocked with carp irrespective of
stocking density (0.5 or 1 fish/m2
), and the predation rate rose more to increased snail infestation
levels than was the case with tilapia . Even as a less effective predator, Nile tilapia significantly
reduced snail numbers compared to the no-fish control particularly in the dry season and at the
higher fish stocking density. Measuring the sizes of surviving snails showed that both fish species
could not prevent larger snails from occurring. By allowing larger snails to survive, biocontrol
with these two species of fish needs to be supplemented by hand removal or screens on inlets.