Streamflow Complexity Associations with the Northern Leatherside Chub at Multiple Spatial Scales

The northern leatherside chub is a species of conservation concern that purportedly has been impacted by anthropogenic activities.  Microhabitat studies have shown the species to select areas with complex streamflows in addition to other habitat features.  While several studies have evaluated the influence of instream habitat on northern leatherside chub at the reach-scale, few have explicitly evaluated associations with habitat complexity at this scale despite field observations suggesting its importance.  We studied the effect of reach-scale complexity in streamflow, water depth, substrate, and cover, in addition to other habitat factors, on northern leatherside chub occurrence in the Goose Creek watershed of the Upper Snake River Basin.  Of the habitat complexity measures we evaluated, streamflow complexity (SD of velocity) in the reach was the predominant factor associated with the species’ occurrence.  Multiple regression revealed that streamflow complexity increased in larger streams and in the presence of beaver dams, but was negatively associated with streambank condition and percent fine substrates.  Our study suggests that streamflow complexity across multiple spatial scales is important to the distribution of northern leatherside chub and that land and wildlife management will play an important role in future conservation efforts for the species.