Date of Award

7-2020

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Biology

First Advisor/Chairperson

Brandon Gerig

Abstract

The widespread establishment of dreissenid mussels (Dreissena spp.) in Lake Michigan has strongly altered energy flow by sequestering nutrients in nearshore benthic habitats. Despite these ecosystem changes, little is known about their influence on resource partitioning in nearshore fish communities. Here we use stable isotope analysis to characterize the contemporary fish community and historic walleye (Sander vitreus) population of Lake Michigan’s Little Bay de Noc. We found species-specific differences in the δ15N and δ13C values for 14 fish species. High degrees of niche overlap between walleye, northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu) and yellow perch (Perca flavescens) indicating shared use of common prey items including round goby (Neogobius melanostomus)]. As length increased, northern pike and smallmouth bass increased their reliance on nearshore resources, while walleye increased reliance on pelagic resources. Isotope analysis over a 31-year time series coincident with the invasion of dreissenid mussels suggests that alterations in energy dynamics influencing walleye were dictated by varied responses from dominant prey items. Furthermore, sex-specific differences in walleye spawning movements indicated that females make significantly greater movements than males possibly driven by higher energetic and reproductive demands. This study improves our understanding of the Lake Michigan ecosystem by informing how whole-scale shifts drive trends in important sport fish communities.

Access Type

Open Access

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