Wednesday, June 6, 2007 - 2:15 PM
263

Competition among juveniles as a potential mechanism for crayfish species displacement in an Ozark river drainage

Eric R. Larson, Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701 and Daniel D. Magoulick, Department of Biological Sciences, USGS, Arkansas Cooperative Fish and Wildlife Research Unit, University of Arkansas, Fayetteville, AR.

The coldwater crayfish Orconectes eupunctus is endemic to the Spring and Eleven Point Rivers of Arkansas and Missouri, and appears to have been displaced from a portion of its range by the recently introduced ringed crayfish Orconectes neglectus. We examined competition among juveniles as a potential mechanism for this crayfish species displacement through laboratory and field experiments. Orconectes eupunctus juveniles survived and grew in stream cages in their former range, implicating biotic interactions rather than habitat degradation in the displacement. Laboratory experiments revealed O. neglectus juveniles were most likely to capture limited food (χ2=11.0, P<0.001), whereas O. eupunctus juveniles were more likely to occupy limited shelters (χ2=11.4, P<0.001). In a field experiment of competition that paired juveniles of both species in stream cages for the summer and fall of 2006, O. neglectus juveniles did not inhibit growth or reduce survival of O. eupunctus juveniles (F=0.588, P=0.455). Results of this study indicate that competition may not be a major factor in this crayfish species displacement and that laboratory evidence of dominance does not necessarily translate into competition in the field.

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