What Limits Invaders? Proposing Habitat Manipulation to Suppress Virile Crayfish, an Aquatic Nuisance Species in the Southwest

Approximately half of species listed under the U.S. Endangered Species Act (ESA) are at risk primarily due to competitions with introduced species. Furthermore, over the past century many fishes endemic to southwestern United States have been listed under the ESA.   Virile Crayfish Orconectes virilis, a southwestern aquatic nuisance species, negatively impact imperiled species, particularly Apache Trout Oncorhynchus gilae apache, a threatened salmonid.  Available control methods are ineffective at suppressing Virile Crayfish.  We developed Apache Trout and Virile Crayfish habitat suitability criteria and assessed criteria overlap to identify habitat management strategies that may favor Apache Trout and suppress Virile Crayfish.   Two parameters limited Virile Crayfish abundance: maximum temperature and water velocity.  Virile Crayfish selected high maximum temperature (>26C), which did not overlap lower maximum temperatures (<26C) Apache Trout selected.   Virile Crayfish selected slower velocity (0-0.2m/s) than Apache Trout (0.1-0.5m/s).  Flash floods displace Virile Crayfish downstream.  We suggest increasing overhead cover (streamside vegetation planting) to reduce stream warming; adding instream cover to increase water velocity; and trapping crayfish after flash floods as potential management strategies to suppress Virile Crayfish and favor Apache Trout.  Native and nonnative species habitat suitability criteria comparisons may provide insight to manage other species interactions through habitat manipulation.