Distribution of aquatic pulmonate snail species in contrasting habitats within the Ross River Reservoir (stage 2a), tropical Northern Australia

Abstract

Monthly distributions of three snail species in three distinct habitat types from February 1992 to May 1993 were found to be variable, with peak abundances occurring predominantly in the late wet season (March to May) for Amerianna carinata and Gyraulus gilberti and in the late dry season (September to November) for Austropeplea lessoni. No consistently positive or negative patterns of correlation were recorded between numbers of snails and physico-chemical characteristics or the amount or composition of emergent and submerged macrophyte species. However, highest densities of A. lessoni and A. carinata were recorded in temporary ponds, where the biomass of periphyton was greatest. Significantly lower amounts of periphyton were recorded from open bays and permanent creeks. Highest densities of G. gilberti occurred in permanent creeks. Physico-chemical variables, rainfall patterns and macrophyte species were not good indicators of snail abundance in the Ross River reservoir. The best indicator of snail density appeared to be whether vegetated habitat is located within open bays, permanent creeks or isolated peripheral ponds.