LAUSR

Abstract Limnoperna fortunei has been dispersing fast across South America by means of anthropic activities, invading aquatic ecosystems and causing substantial ecological and economic changes. Among these changes, L. fortunei has the potential to become an important prey species, and studies have verified their consumption by several fish in the South American continent. However, the impacts of fish predation on mussel densities have not yet been quantified. The present study had as a main objective the experimental evaluation of the potential impact of predation by piapara M. obtusidens on the densities of L. fortunei. Thus, a short-term experiment of predation in a fish farm was conducted in the upper Parana River basin, Brazil. The exposure to predation by adults of M. obtusidens consistently reduced the biomass of L. fortunei with the level of impact increasing significantly as the density of predators and period of exposure increased. The observation of several substrates with a total removal of mussels indicated that all size classes of shells were preyed. Megaleporinus obtusidens presents various determining characteristics for the predation success on L. fortunei in confined areas, such as resistance to non-natural conditions, and mouth apparatus able to both remove several sizes of mussels on rigid substrates, and break apart the shells. The results of this experiment indicate the important role of predation in reducing the population densities of L. fortunei, as well as the potential use of M. obtusidens as an auxiliary tool for the maintenance of integrated invasive species prevention mechanisms.