Using Cleithrum Morphometrics to Identify and Estimate the Total Length of Yellow Perch Piscine Prey Items in Southwestern Lake Michigan

Reconstructing the composition and lengths of piscine prey items is essential for evaluating prey selectivity, percent composition, and biomass of predator diets. Bony structures including vertebrae, pharyngeal arches, dentaries, and cleithra have been used to accurately identify and estimate the total length of digested prey items. Within Lake Michigan, numerous non-native species have become established and contribute significantly to the diets of native piscivores such as yellow perch. We examined the relationship between cleithrum length and total length for yellow perch, round goby, alewife, and spottail shiner. Cleithrum morphometrics were then used to identify and estimate the total length of piscine prey items found in the diets of yellow perch. The relationship between cleithrum length and total length was significant for all species with coefficients of determination exceeding 0.90. Round goby were the most frequently consumed prey fish, found in the diets of yellow perch >70 mm total length. Our results indicate that cleithra preserved in stomach contents permit accurate reconstruction of prey identity and total length. Applied to yellow perch stomach contents, cleithrum morphometrics enabled us to evaluate size-selective predation and determine that non-native species allow yellow perch to transition to piscivory earlier in life than previously documented.