Long-Term DNA Retention in Sea Lamprey Digestive Tracts

Sea lamprey (Petromyzon marinus) are a parasitic invasive species in the Great Lakes, causing significant damage to native fish populations and fisheries. Traditional diet assessments rely on wound observations, which may not allow for a comprehensive understanding of the impacts from lamprey predation. Recent advances in molecular technology, such as DNA metabarcoding, may allow for the indentification of host fish species from DNA extracted from sea lamprey digestive tracts. However, questions remain on the persistence of DNA within sea lamprey digestive tracts given factors such as temperature fluctuations or fasting duration. Additionally, sea lamprey can feed on multiple hosts, potentially leading to biases in DNA detection.To address these uncertainties, we used controlled feeding experiments to examine how long host fish DNA remains detectable in sea lamprey after feeding and how these factors affect DNA degradation. Lamprey were fed on lake trout (Salvelinus namaycush) and subjected to fasting periods of up to 30 days at different temperatures (5C, 10C, and 15C). Additional trials tested whether DNA from multiple hosts could be detected when lamprey fed on different species consecutively.Results showed that host DNA remained detectable for up to 30 days post-feeding, with detection probability decreasing over time. Temperature influenced DNA degradation, but its effect varied depending on fasting duration. Lamprey that fed on multiple host species retained DNA from both, allowing for the reconstruction of feeding histories beyond the most recent meal. These findings confirm that DNA metabarcoding is a powerful tool for assessing sea lamprey diets, even when individuals have fasted for extended periods.This study improves dietary analysis methods for sea lamprey and enhances our understanding of their ecological impact. By refining techniques for host species detection, these results will help improve estimates of lamprey-induced fish mortality and support management strategies aimed at controlling their populations in the Great Lakes.