Date of Award:

8-2020

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Sarah E. Null

Committee

Sarah E. Null

Committee

Jeffery S. Horsburgh

Committee

Brett B. Roper

Abstract

Rivers provide habitat for aquatic species, but widespread human water development degrades aquatic habitat, fragments stream networks, and threatens native fish populations. Habitat suitability models are commonly used to identify current instream habitat conditions, but are often species-specific, data-intensive, and rarely suitable to the large spatial scales required in conservation and water resources management. Thus, there is need to develop and validate habitat suitability models that provide ecologically-meaningful estimations of aquatic habitat, but are simple enough to apply at large geographic areas and flexible to incorporate different species. I tested the accuracy of 15 habitat suitability models estimating Bonneville Cutthroat Trout and Bluehead Sucker monthly habitat suitability in Utah perennial streams using unique combinations of four modeled environmental variables; percent mean annual discharge, velocity, gradient, and stream temperature. Modeled discharge and stream temperature matched observed values well, explaining 78-89% of variability in the observed data. Habitat suitability model accuracy varied considerably, but simple models including fewer variables than considered in this study most accurately predicted Bonneville Cutthroat Trout and Bluehead Sucker habitat suitability. Temperature best predicted Bonneville Cutthroat Trout habitat suitability, while gradient and percent mean annual discharge best predicted Bluehead Sucker habitat suitability. Utah stream networks were highly fragmented by instream barriers, but connectivity decreased significantly in May and June when habitat suitability was considered. This work demonstrates that habitat suitability models can accurately estimate habitat suitability when generalized for multiple species and large spatial scales, and that additional variables do not necessarily improve model accuracy. The modeling approach expands current methods for quantifying aquatic habitat conditions for use in conservation and water resources planning.

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