Date of Award

2012

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Earth and Environmental Sciences

Keywords

Lake Erie, PCR, stomach contents, yellow perch

Supervisor

Daniel D Heath

Supervisor

Timothy B Johnson

Rights

info:eu-repo/semantics/openAccess

Abstract

The western basin of Lake Erie receives input from two main tributaries (Maumee and Detroit River), which differ greatly in their nutrient and sediment loading. The higher turbidity of the Maumee River plume is thought to reduce predation on early-stage juvenile yellow perch (Perca flavescens), consequently increasing their survival. For this reason, my overall objective was to evaluate the effect of the Maumee River plume on the overall recruitment of larval yellow perch to the juvenile stage. However, traditional diet analyses are not effective for evaluating larval predation rates. I therefore review genetic and non-genetic diet analysis techniques, and how they have evolved with technological advances, allowing researchers to effectively explore trophic interactions and energy movement in aquatic ecosystems. This provided a framework for my doctoral research for which I used a variety of molecular genetic techniques to estimate survival of larval yellow perch using population genetics and predation rates through stomach content analysis of predator fish. Using yellow perch microsatellite markers, I measured temporal and spatial genetic structure in larval yellow perch, while Bayesian genotype assignment provided relative larval survival estimates for yellow perch inhabiting the Maumee and Detroit River plumes. Overall, genotype assignment of Age-0 yellow perch establishes that, in the western basin of Lake Erie, larval recruitment to the juvenile stage is significantly higher for fish inhabiting the Maumee River plume relative to those in the Detroit River plume. In addition, I utilized molecular genetic techniques to accurately identify highly digested early-stage juvenile prey to the species level which was not possible with a more traditional approach (visual inspection of gut contents). Specifically, I use polymerase chain reaction (PCR), cloning and sequencing, to demonstrate the diversity of prey consumed by several freshwater fish species. Finally, using species-specific single nucleotide polymorphism (SNP) assays and microsatellite markers, I quantified predation and cannibalism experienced by larval yellow perch in the Maumee and Detroit river plumes. The combination of markers showed generally higher predation and cannibalism in the less turbid waters of the Detroit River plume, indicative of river-plume effects (possibly mediated through turbidity) reducing larval yellow perch predation mortality. My doctoral research shows the likely mechanism that river plumes in the western basin of Lake Erie contribute to larval yellow perch survival and consequently potential recruitment; however, temporal and spatial variability indicate that other factors also contribute.

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