Data from: Distribution, population dynamics and potential impacts of the invasive snail, Tarebia granifera in aquatic ecosystems of north-eastern South Africa

Aquatic ecosystems globally have been invaded by molluscs. Tarebia
granifera is a highly successful invader, often becoming the dominant
aquatic invertebrate species in an invaded ecosystem. Resultingly, it has
been suggested that T. granifera may have severe negative impacts on these
invaded ecosystems. Limited information is available regarding the
population structures and densities of T. granifera, particularly in
invaded countries such as South Africa, and information on this could
assist in developing management and control strategies for this invasive
species. The aim of the present study was to assess the current
distribution, densities, and population structures of T. granifera in
invaded habitats on the Limpopo and Phongolo River systems, South Africa.
This was accomplished by collecting aquatic benthic molluscs from sites
across these systems. Water quality parameters were measured at each site
and water samples collected for chemical nutrient analyses. The density of
snails was determined for each site and the population size and structure
as well as birth rate was calculated for T. granifera. Tarebia granifera
was found to be the dominant molluscan species in habitats where it was
present and all size classes from new-born to mature adults were found
throughout at some of the highest densities globally. Worryingly, native
molluscan species, were often absent or in much lower densities than
reported in literature at sites where T. granifera was present, suggesting
a negative effect on the native molluscan density and diversity. Contrary
to most previous studies, there were no significant correlations between
T. granifera and the selected water quality parameters. Higher densities
and new-born recruitment of T. granifera were observed in the spring than
autumn, likely in response to shifts in environmental conditions. This
study provides crucial insights into the population structure and dynamics
of T. granifera in invaded habitats, particularly for relatively newly
invaded regions such as southern Africa.