Habitat Selection by Apache Trout in Six East‐Central Arizona Streams

Abstract

Abstract Information on habitat selection by Apache trout Oncorhynchus gilae apache is needed to help recovery efforts for this federally threatened species. We investigated Apache trout habitat selection in six White Mountain streams in east‐central Arizona. We measured environmental characteristics at used sites and randomly selected available sites and modeled habitat selection using forward step‐wise logistic regression, for two size‐classes of Apache trout (≤100 mm and >100 mm total length [TL]). We also compared overall habitat type selection using contingency table analysis and G ‐tests. Our logistic regression models correctly predicted habitat selection by 100‐mm TL or smaller Apache trout for 62.8% of sites over all streams surveyed and that by Apache trout larger than 100 mm TL for 75% of sites. Logistic regression models determined that larger width, lower width: Depth ratio, more eddy flows, and more cover in the form of overhanging vegetation, debris, and boulders were significant predictors for locations of Apache trout larger than 100 mm TL. Slower current velocity was the only significant predictor for locations of Apache trout 100 mm TL or less. Contingency table analysis indicated that in five of six streams, Apache trout had a greater frequency of occurrence in pool habitat. Habitat management techniques that shift stream conditions toward slower current velocities, larger widths, lower width: Depth ratios, more eddy flows, and increased cover (overhanging vegetation, debris, and boulders) should be implemented. This may mitigate for Apache trout habitat loss and may lead to an increase in the species' production.