Absence of shared mitochondrial DNA haplotypes between sea lamprey from North American and Spanish rivers

Sea lamprey Petromyzon marinus from the River Miño and Sella, Spain, showed an almost identical frequency for three observed haplotypes. None of these haplotypes were found among three North American populations. These results indicate an absence of exchange among sea lamprey populations spawning in the west and south‐east Atlantic coasts. The similarity between the collections from the two Spanish rivers suggests that homing does not occur in anadromous sea lamprey.