American Eels consume invasive Sea Lamprey larvae

Abstract Objective Little is known about potential predators of Sea Lamprey Petromyzon marinus in Lake Champlain and the Laurentian Great Lakes. However, such information could provide valuable insights for a wider view of ecosystem-level lamprey control. We hypothesized that American Eels Anguilla rostrata could be major predators of Sea Lamprey larvae. Methods We tested our hypothesis using laboratory experiments and field observations. Specifically, we tested whether (1) eels would consume lamprey in experimental mesocosms, (2) eels would eat lamprey when alternate prey were available in the same mesocosms, and (3) lamprey could be detected in the guts of wild-caught eels using genetic analysis of gut contents. Results Our results indicate that eels can and will consume lamprey under experimental settings even when alternate prey are provided; lamprey were consumed in 26% of lamprey-only trials and 21% of trials where alternate prey were available. Genetic analysis of gut contents collected by gastric lavage from wild-caught eels in areas overlapping larval lamprey habitat identified lamprey DNA in 40% of samples, confirming that eels do consume lamprey in the wild. Conclusions Given the observed prevalence of lamprey consumption by eels, our study suggests strong potential value in conservation efforts for native predatory fishes, such as the imperiled American Eel, as an additional tool for Sea Lamprey management.