Abstract
The apple snail, Pomacea canaliculata (Lamarck), is an important exotic pest in paddy fields in Japan. In Shizuoka Prefecture after the first occurrence in 1983, the distribution area of the snails has been increasing year by year. We conducted a mark-release-recapture study of the snails in paddy fields with plot-to-plot irrigation to investigate their dispersal ability. The recapture rates were about 60% at two weeks after the release. About 30% to 60% of the snails moved from a released field to the adjoining fields through water inlets. After the invasion to the adjoining fields, they dispersed widely over the paddy fields. The maximum movement distance was 68m, although most of the snails moved less than 30m.
