Negative effects of Corbicula fluminea over native freshwater mussels

The global decline of freshwater mussels is related with a great variety of factors, including the introduction of invasive species. However, the possible effects of other invasive bivalves, such as the Asian clam Corbicula fluminea (Muller, 1774), remain mainly unknown and highly speculative with very few manipulative experiments addressing this issue. In this study, field and laboratory experiments were conducted to assess the possible negative effects of C. fluminea on the native freshwater mussel Unio delphinus Spengler, 1783. Growth, physiological condition, and the locomotor activity were assessed in U. delphinus at increasing C. fluminea density. U. delphinus exhibited lower growth, lower physiological condition, and higher locomotor activity at higher C. fluminea density, which may suggest that this unionid is negatively affected by C. fluminea and may be displaced to less favorable habitats. Although we were not able to establish the main mechanism(s) responsible for these results, possibilities include competition for food resources, competition for space which may result in mussel displacements and/or changes in microhabitat features as a result of bioturbation activities, and production of feces and pseudofeces by C. fluminea.