Potential Impacts of the Invasive Rusty Crayfish (Orconectes rusticus) on the Native Gastropod Communities of the Susquehanna River

Elaine Langone Center, Terrace Room

The rusty crayfish (Orconectes rusticus) is a well-studied and highly invasive species of the Susquehanna drainage in Pennsylvania. It can survive in lakes, rivers, and streams and is capable of outcompeting native species such as Orconectes obscurus for food and habitat. O. rusticus is discernibly larger and more aggressive than O. obscurus, and can survive in a wide variety of habitats and extreme conditions, more so than other species of Orconectes. We sought to investigate predation rates on different gastropod species native to the Susquehanna River system, by both O. obscurus and O. rusticus. In addition, gastropod densities and communities were assessed at 7 longitudinal sites along roughly 200 miles of river. Through laboratory mesocosm experiments, we assessed predation rates on Physella acuta, Leptoxis carinata, and Pleurocera virginica, three snail species common to the Susquehanna drainage. We placed a mixed size-class of adults and/or juveniles into a mesocosm with one crayfish (O. rusticus or O. obscurus) for a 48 hour period. O. rusticus was found to have a mean predation rate of >90% on P. acuta, >35%on L. carinata, and 0% on P. virginica. O. obscurus was found to have a mean predation rate of >65% on P. acuta, >10% on L. carinata, and <1% on P. virginica. Consequently, O. rusticus exhibited higher mean predation rates on smaller, softer-shelled gastropods than O. obscurus. Our preliminary findings show P. virginica exhibiting the highest densities throughout our sites, and P. acuta exhibiting the lowest densities. Our findings suggest that an invasion of not only has the potential to outcompete and extirpate native crayfish species, but also to decrease species diversity among native gastropods to the Susquehanna watershed.