Date Approved


Graduate Degree Type


Degree Name

Biology (M.S.)

Degree Program

Annis Water Resources Institute

First Advisor

Carl Ruetz III

Second Advisor

Tomas Höök

Third Advisor

Devin Bloom

Academic Year



To better understand stock structure and identify potential selective pressures, I characterized the morphological variation of adult Yellow Perch (Perca flavescens) inhabiting Lake Michigan and connected water bodies. I collected Yellow Perch from nearshore Lake Michigan and littoral and profundal habitats within six drowned river mouth (DRM) lakes. I quantified the morphological diversity of Yellow Perch using both geometric morphometrics and linear measurements. I found that Lake Michigan Resident Yellow Perch had slender bodies, short heads, small eyes, and long pectoral fins. Lake Michigan Migrants had intermediate body depths, downward pointed heads, and a range of pectoral fin lengths and eye sizes. Littoral DRM Residents had deep bodies, long and downward pointed heads, large eyes, and short pectoral fins. Profundal DRM Residents had deep bodies, long and upward pointed heads, and large eyes. My results show that littoral habitat (in DRM lakes) likely favors deep body depths, long heads, and large eyes, which matches expectations for divergence between shallow- and deep-water habitat. Deeper habitat (i.e., nearshore Lake Michigan and DRM-profundal) likely favors longer pectoral fins, which was unexpected and may be due to foraging on the benthos in profundal habitat. Additionally, Yellow Perch that moved between Lake Michigan and DRM Lake habitat (Lake Michigan Migrants) generally exhibited a comparatively large amount of morphological variation, which I hypothesize is due to the diverse ecological challenges fish face by inhabiting both habitats. My findings indicate that morphological variation is present among adult Yellow Perch inhabiting Lake Michigan and connected water bodies, providing further evidence of intraspecific variation within this species in the Laurentian Great Lakes and that the number of morphologically distinct types extends beyond those identified through genetic analysis in the same area.

Available for download on Wednesday, May 12, 2027