Date of Award:

5-2005

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Department name when degree awarded

Aquatic, Watershed, and Earth Resources

Committee Chair(s)

Chris Luecke

Committee

Chris Luecke

Committee

Wayne Wurtsbaugh

Committee

Frank Messina

Abstract

Benthic Bear Lake whitefish (Prosopium abyssicola) and Bonneville whitefish (P. spilontus) are closely related, yet the extent of ecological separation remains poorly understood. We described their spring and summer distribution and diet in Bear Lake and examined how these were related to environmental growth conditions, and predation risk. In spring and summer, Bonneville whitefish dominated shallower depths (5-30 m), whereas Bear Lake whitefish dominated deeper depths (45-55 m). At intermediate depths (35-40 m), low numbers of both species occurred. Bonneville whitefish ate mostly Chironomidae, whereas Bear Lake whitefish ate mostly Ostracoda. Habitats occupied by Bonneville whitefish had better growth conditions, but higher predation risks compared to Bear Lake whitefish habitats. Avoided habitats had poor growth conditions and high predation risk. These data describe an ecologically distinct, whitefish community in an ecoregion different from those studied before. Whitefish may maintain higher survival at shallow or deep but not middle depths.

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