The invasive apple snail Pomacea canaliculata in Indonesia: a case study in Lake Rawa Pening, Central Java.
The occurrence of the invasive apple snail Pomacea canaliculata in Indonesia was first reported in 1984. The species was introduced as an ornamental aquarium pet. Since then, people have begun to culture the snail in ponds usually adjacent to rice fields. When it was realized that the species multiplied rapidly and was a serious pest, this invasive apple snail had already spread widely. There are many cultural methods of controlling and preventing its distribution, but none are effective in keeping them at non-damaging levels. We mapped the distribution of P. canaliculata in Indonesia from the MZB's collections as well as literature references and found that the snail invaded almost all large islands, such as Sumatra, Java, Kalimantan, Sulawesi, Maluku, and West Papua. We also studied the impact of P. canaliculata on the native apple snails P. ampullacea, P. scutata, and P. virescens in Lake Rawa Pening (a popular tourism destination) as a case study. The results showed that two species of Pila already disappeared from Lake Rawa Pening. Only P. scutata occurs still in the region and was found alive usually in shallow water and rice fields surrounding the lake. To resolve the problem we recommend that cleaning the lake periodically from the invasive aquatic weed Eichhornia crassipes (known to locals as "eceng gondok") by a private company and harvesting the weeds for the local small craft industry by the local fishermen could be an alternative measure to reduce the population of the P. canaliculata, as well as collecting P. canaliculata for local food or for feeding ducks. Rearranging the number of fish-pens "karamba" and their location in the lake could be seen as an alternative way also for reducing the population of P. canaliculata, since the snails lay their egg masses on the bamboo stakes of "karamba." Such rearrangement could make the landscape more attractive for tourism.