Document Type

Thesis

Date of Degree Completion

Summer 2013

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Kristina Ernest

Second Committee Member

Lixing Sun

Third Committee Member

Paul James

Abstract

Beaver reintroduction programs are increasingly being viewed as a way to enhance salmonid habitat and production. However, the actual effectiveness of using beavers as a habitat enhancement tool for ESA listed steelhead Oncorhynchus mykiss populations is unknown. We examined the type of habitat, at both the microhabitat and mesohabitat levels, preferred by steelhead in three small streams in the upper Yakima Basin, WA through standard snorkel surveys and habitat measurements. Our results suggest that steelhead in small streams strongly prefer (relative to availability) microhabitats that have deeper water(> 30 cm), slow stream velocities(< 0 .05 mis), and complex cover types. Habitat partitioning among the size-classes (small< 50 mm, medium 50-90 mm, large> 90 mm total length, TL) principally operated around water depth and to a lesser extent around stream velocity, with larger steelhead (> 90 mm TL) occupying slower and deeper water than smaller steelhead (< 90 mm TL). Mesohabitat analyses indicate that all size-classes of steelhead avoid riffles and strongly prefer pool habitat, while only large steelhead (> 90 mm TL) strongly prefer beaver pond habitat and small steelhead (< 50 mm TL) prefer glides. Consequently, in small streams the creation of deep pool habitat, either through artificial means or through beaver reintroduction programs, will be beneficial for increasing the amount of highly preferred habitat for steelhead populations.

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