Habitat suitability criteria for Virile Crayfish, a non-native species in Arizona

Authors: Sally Petre, Scott A. Bonar

Year: 2013 (xlv)

Abstract

Introduction of non-native species can influence survival of native species. Virile Crayfish, Orconectes virilis, introduction in the southwestern United States, particularly Arizona, is a serious concern due to their potential negative effect on imperiled native fish and invertebrates. Although currently control methods have been unsuccessful in natural stream systems, certain habitat parameters might be altered to disfavor crayfish. Here we show habitat suitability criteria for Virile Crayfish in Arizona streams. Future research will compare favored habitat for Virile Crayfish with habitat criteria for other managed species. We sampled streams containing Virile Crayfish using a quadrat sampler to identify occupied and unoccupied locations and measured habitat parameters (water velocity, depth, substrate, in stream cover, overhead cover and temperature) at each location. For each parameter, habitat ranges occupied were compared to those available to assess preference. There were no significant differences in habitat use between sexes (P>0.05). Juveniles were more selective than adults, preferring shallower water than adults (P<0.001). Of the habitat parameters investigated, Virile Crayfish preferred a wide range of available habitat except for high velocity. With increasing velocity, we found decreasing crayfish abundance and low preference for high velocities. After a high flow event (high velocities) we found significantly less crayfish in an area than before the flood event, which suggests that the crayfish are swept downstream. Virile Crayfish are non-burrowing crayfish and have a low slip sleep, thus are easily washed downstream. Our management suggestion to significantly reduce Virile Crayfish abundance in an area is to trap them from an area after or during a high flow event. We hope to use this assessment of habitat suitability criteria as a tool to better understand environmental factors that limit Virile Crayfish and use this information to limit their interactions with other native species, especially Apache Trout, Oncorhynchus gilae apache.