| Zusammenfassung: | Introduction of nonindigenous crayfish species impacts freshwater ecosystems and can result in displacement of native crayfish. The crayfish Orconectes limosus and Cambarus bartonii are native to the Susquehanna River drainage in Pennsylvania. However, several nonindigenous crayfish have become established in this drainage. No comprehensive survey exists on crayfish species within the Fishing Creek watershed. Historic records report O. limosus and C. bartonii in this watershed; however, recent point surveys have documented the presence of the nonindigenous crayfish O. obscurus. We sampled crayfish in 15 sites from the lower reaches of Fishing Creek through its headwaters and major tributaries. We collected a total of 484 crayfish, representing the species O. obscurus and C. bartonii. We found O. obscurus within much of Fishing Creek and some tributaries, but absent from the upper reaches of the watershed, possibly due to a series of dams. C. bartonii were primarily found in the upper portions of the Fishing Creek watershed, but also found at low abundance with O. obscurus in the central portions of the watershed and in a small, first order tributary. We collected no O. limosus specimens in our samples, suggesting local extirpation via displacement by O. obscurus, as has been reported elsewhere.
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