Habitat Suitability Criteria for Apache Trout
August 2011 to May 2014
In the past 60 years, native fish species endemic to the southwestern United States have declined in abundance and range, resulting in the federal listing of the majority of these species (70%) under the Endangered Species Act (ESA). Apache trout, Oncorhynchus giliae apache, a salmonid endemic to the White Mountains of east-central Arizona, is listed as threatened under the ESA. Major reasons for the decline and listed status of Apache trout include overfishing, drought, negative species interactions (nonnative salmonids and crayfish) and habitat degradation. In order to maintain and successfully manage populations, managers need to know the parameters for suitable Apache trout habitat so that fish are stocked in areas with the highest survival and reproduction probabilities. This study is designed to develop habitat suitability criteria for Apache trout that will give managers the information to make informed decisions about recovery stream selection and barrier placement. Also, comparing habitat suitability criteria for other species (non-native salmonids or crayfish) to that of Apache trout will aid in understanding habitat usage and potential problem areas among species. We sampled three Apache trout streams, the West Fork of the Black River and East and West Forks of the Little Colorado River, to identify where fish were located (occupied vs. unoccupied) and measured habitaft parameters (flow in ft/sec, depth, substrate,
instream cover, overhead cover and temperature) at these occupied locations and unoccupied locations. These data were analyzed to determine quantitative habitat parameters suitable or preferred by Apache trout. Apache trout are likely to be found in areas with instream cover such as large woody debris (fallen logs/log jams), overhanging banks or aquatic vegetation, deep areas such as pools, and are limited in their range by suitable temperatures. A thesis has been completed on this work, and now results are being prepared for publication.