Genetic dietary analysis has been a rapidly growing area of study due to several advantages it holds over conventional methods, such as enhanced taxonomic resolution and the ability to detect rare or degraded prey items. In this thesis, DNA metabarcoding is applied to investigate the dietary composition of parasitic, hematophagous sea lamprey (Petromyzon marinus) within the Great Lakes region. This approach aims to enhance our understanding of sea lamprey feeding habits by addressing limitations with traditional diet assessment methods, ultimately contributing to more informed management efforts. The first objective was to design a blocking primer that selectively suppresses amplification of sea lamprey DNA at the 12S rRNA gene region, allowing for clearer observations of host fish DNA detections. With a successful blocking primer, the second objective was to assess the influence of different environmental and biological variables on the retention of host fish DNA in sea lamprey digestive tracts within a controlled setting. Specifically, various temperatures and post-feeding fasting periods were examined in experimental aquaria, along with the ability to detect multiple hosts after sea lamprey had consecutively fed on different species. Results demonstrated that host DNA could remain detectable in sea lamprey digestive tracts for up to 30 days at temperatures between 5-15°C and still produce sequence reads from feedings on multiple host species. In the third objective, DNA metabarcoding was applied to wild-caught sea lamprey samples to assess the applicability of this technique in the field. Both adult and juvenile parasitic sea lamprey were collected from Lakes Huron, Superior, and Champlain during 2022 and 2023, with findings indicating potential sources of dietary differences among lakes and life stages for Great Lakes sea lamprey. Together, these results underscore the utility of DNA metabarcoding in detecting and distinguishing prey taxa, with valuable applications towards sea lamprey management strategies in the Great Lakes.
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