Turbid River Plumes Benefit Fish Recruitment through Reduced Larval Predation: A Novel Molecular Genetic Approach

Predation on larvae appears critical to predicting fish recruitment in freshwater and marine ecosystems. However, its quantification via stomach content analyses often fails due to rapid digestion rates. Here, we use novel molecular genetic methods to quantify predation on larval yellow perch Perca flavescens inside and outside of the Maumee River plume (MRP) in western Lake Erie, testing the hypothesis that turbid river plumes benefit recruitment.  We analyzed >1700 stomachs from common predators (walleye Sander vitreus, white perch Morone americana, and white bass M. chrysops) during the larval yellow perch production period over 3 years. We screened stomach content DNA for yellow perch using a single nucleotide polymorphism (SNP) marker. Stomachs positive for the SNP marker were genotyped at five microsatellite loci and the alleles recovered were used to estimate the number of larval yellow perch in each predator’s stomach.  Our results showed reduced predator abundance combined with lower predation rates explain enhanced recruitment of larval yellow perch inside versus outside of the MRP. Our findings highlight the power of molecular genetics in the study of trophic interactions and how turbidity associated with river plumes can benefit fish recruitment by reducing predation mortality during the larval stage.