Introduced alien ringed crayfish (Orconectes neglectus neglectus [Faxon, 1885]) threaten imperiled coldwater crayfish (Orconectes eupunctus Williams, 1952) in the Eleven Point River drainage, Missouri, USA

Abstract

The Eleven Point River drainage in the Ozarks ecoregion of North America contains the largest known populations of and critical habitat for the globally imperiled coldwater crayfish (Orconectes eupunctus). We present here the discovery of an introduced population of alien ringed crayfish (Orconectes neglectus neglectus) in Jolliff Spring Branch in the upper reaches of the drainage. Sampling was conducted at eight sites throughout the tributary to determine the extent of the alien species’ range in the stream. Orconectes n. neglectus were found at four sites extending along 3.4 km of stream, with reproducing populations confirmed at two upstream sites, and few individuals found at two others. This invasion represents a threat to O. eupunctus, which occurs a few kilometers further downstream in the drainage and has been recorded from only the lower reaches of Barren Fork and throughout the mainstem Eleven Point River. Introduced O. neglectus were previously associated with localized extirpation of O. eupunctus in another drainage. Study results warrant monitoring of the invasion and possible reassessment of the conservation status for O. eupunctus.