A multi-indicator approach to dietary assessments within Lake Michigan's nearshore area

Fundamental to understanding species ecology, is the evaluation of predator-prey interaction strengths and their spatial heterogeneity. Traditional dietary assessment methods of examining individual’s stomach contents provide valuable data quantifying relationships, however what is incorporated into organisms is not always proportional to what is consumed. Biochemical compounds have recently been explored in marine and terrestrial systems to obtain relatively less variable data than stomach contents and provide multiple meal integrated data associated with growth, development, and condition of predators. Stable isotope ratios have been used to infer community structure for decades, while fatty acid signatures have only recently been used in terrestrial and marine systems to explore dietary trends. Using a data set collected from Lake Michigan throughout the 2010 intensive sampling year, I: 1) examined foraging patterns of juvenile yellow perch (Perca flavescens) using stomach content, fatty acid signature, and stable isotope analyses; 2) employed stomach content, fatty acid signature, and stable isotope analyses to examine how dietary overlap questions can be addressed through multiple dietary indicators. With this data set I was able to depict a spatial divide in juvenile yellow perch diets based on shoreline and habitat, demonstrating the utility of combining stomach content and fatty acid signature analysis. Throughout the methodological studies, stomach content data was found to provide highly variable data, but was invaluable in identifying prey taxa. Fatty acid signature analysis proved highly useful in its ability to describe intraspecific dietary trends, however without further experimentation, dietary overlap indices are impractical. Stable isotope ratios extended turnover rates encompassed migrations and ontogenetic shifts which need to be taken into consideration when future dietary studies are being designed. Overall, it is highly advisable to use biochemical techniques in tandem with stomach content analysis in order to strengthen our abilities to describe and quantify diets of species