Investigation of Crayfish Populations in the Middle Creek Watershed and the Potential Impact of Invasive Orconectes Rusticus on Native Ecosystems

Orconectes rusticus is an invasive species whose presence has spread and grown in many areas of the United States and Canada, and has impacted waters in southeastern Pennsylvania. The rusty crayfish (Orconectes rusticus) has had a significant negative impact on native crayfish populations and has had great success outside of the species’ native Ohio River Basin habitat, thus native ecosystems and food webs have been effected. Orconectes rusticus has been documented in the Middle Creek watershed, though to what extent they have invaded the watershed and whether or not they have completely decimated native populations remains generally unexamined. This study comprehensively assessed the current crayfish population composition, distribution, and density across the Middle Creek watershed. A sum of 20 tributary and main branch sites were chosen to analyze the entire spread within the watershed. A 1.0 x 1.0 m2 quadrat sampler, consisting of a metal frame, mesh netting, and a mesh bag, was utilized to collect crayfish from each site. The placing of the frame was chosen based upon representative habitat, and the crayfish were collected by first hand-netting within the frame and then raking the substrate to a depth of 20 cm. Orconectes rusticus were found throughout the watershed, and populations of the native Cambarus bartonii bartonii were found in some areas, as well. Population health of Orconectes rusticus and Cambarus bartonii bartonii was assessed quantitatively through population densities, length, weights, and sex ratios. To determine the potential impact of Orconectes rusticus on native aquatic food webs through foraging and predation, diet assessments will be conducted through dissection and identification of stomach contents