Walleye diet stable isotope analysis on Black Lake, MI

Abstract

Walleye populations have been decreasing in Black Lake. A diet analysis of Black Lake walleye could show the walleye’s place in the food web and potentially help determine the reason for their decline in population. This study examines diet to determine what walleye are eating in the lake. By looking at the overlap of stable isotope signatures of walleye (average δ15N 8.2, average δ13C -31.27) and possible prey species, walleye were found to eat common shiner (average δ15N 7.4, average δ13C -30.3). At least one prey species was missing from the analysis since there was no expected clumping around the walleye stable isotope signature. In a study conducted on a Canadian Shield Lake, the signature for the most commonly cited prey species, yellow perch was determined (average δ15N 11.3, average δ13C -28.4). Since this isotopic signature is close to that of walleye, and assuming that yellow perch in Black Lake have similar isotopic ratios, it was analyzed in place of yellow perch from Black Lake. Using a linear mixing model walleye in Black Lake could hypothetically be eating a higher percentage of common shiner. Further analysis of isotope signatures of larger, pelagic fish such as yellow perch should be done in order to find the missing walleye prey species.