Status of Native and Invasive Crayfish in Ten National Park Service Properties in Pennsylvania

Lieb, David; Carline, Robert; Ingram, Hannah

This study examines the impact of introduced exotic crayfish on native crayfish populations in 42 Pennsylvania streams located within 10 widely spaced National Park Service (NPS) properties. A collection of 1,246 crayfish belonging to seven species were found, including a threatened and reproducing population of Cambarus (Puncticambarus) sp. at VAFO. Efforts to prevent future introductions of exotic crayfish are needed if the NPS’s aquatic resources are to be preserved. We surveyed 42 streams located within 10 widely spaced National Park Service (NPS) properties in Pennsylvania. Our goal was to collect a sample of all the surface-dwelling crayfish species from each site. Our surveys resulted in the collection of 1,246 crayfish belonging to seven species. Cambarus bartonii was found at most sites and was usually the most abundant crayfish collected; whereas, other native species were either limited to NPS properties in the western (Orconectes obscurus) or eastern (Orconectes limosus) part of the state and were often less abundant. Exotic species (Orconectes rusticus, Orconectes virilis) dominated most of the sites where they were found but were generally restricted to southcentral Pennsylvania. Collections of Cambarus (Puncticambarus) sp. and Procambarus sp. were limited to a few individuals from a few sites. These results indicate that at least 60% of the surface dwelling crayfish species that are known to occur in Pennsylvania are found on NPS properties. The presence of a reproducing population of Cambarus (Puncticambarus) sp., which is probably one of the most threatened aquatic species in the state, at Valley Forge National Historic Park (VAFO) is particularly noteworthy. Unfortunately, exotic crayfish are a major problem for some NPS properties with several streams that support high densities of exotics completely devoid of natives. Additionally, one rusty crayfish was found in the Upper Delaware Scenic and Recreational River (UPDE) property indicating that the park may be in the very early stages of a rusty crayfish invasion. Efforts to prevent future introductions of exotic crayfish and protect existing populations of native crayfish from urbanization and associated habitat destruction are needed (particularly at VAFO) if the NPS’s aquatic resources are to be preserved.