Crowley, S.; Kess, T.; Bentzen, P.; Neville, V.; Bloom, C.; Smith, N.; Fahner, N.; Berghuis, L.; Hobrecker, K.; Hajibabaei, M.; Duffy, S.; Bradbury, I.

American and European Eels (Anguilla rostrata and Anguilla anguilla, respectively) are sister species of conservation concern, as they have declined in abundance in recent decades. Although there is evidence of gene flow between the two species, most previous hybrid detections have been found in Iceland. Here we expand upon existing reports of interspecific hybrids using a combination of an environmental DNA (eDNA) survey and whole genome sequencing of 347 eels from Newfoundland and Labrador. Metabarcoding of eDNA samples at multiple loci detected the presence of European Eel mitochondrial DNA (mtDNA) at eight locations primarily along the south coast of Newfoundland. Genome sequencing of eels collected in the region revealed three hybrid individuals with levels of European admixture consistent with one first generation hybrid and two North American backcrosses, all with European mtDNA. This work supports the presence of a previously unknown, seemingly localized region of hybrid occurrence in southern Newfoundland and expands our understanding of the relationship between these species across the North Atlantic.