Occurrence of Invasive Red Swamp Crayfish (Procambarus clarkii) in the Susquehanna River Basin

Invasive crayfish are considered a serious threat to native crayfish and other aquatic organisms in North America. Here, we report what is, to our knowledge, the first formal documentation of Procambarus clarkii (Girard) (Red Swamp Crayfish) within the Susquehanna River basin in the eastern US. We collected 9 individuals consisting of multiple size classes (indicative of an established population) from a small public fishing pond situated in a wetland complex in Lycoming County, PA, adjacent to a tributary of the West Branch Susquehanna River. We speculate that this population was introduced via live bait, aquarium release, or commercial sportfish stocking. Red Swamp Crayfish may have adverse ecological impacts if further spread continues within the Susquehanna River basin.