Mitochondrial DNA Analysis Indicates Sea Lampreys Are Indigenous to Lake Ontario

Abstract

The parasitic sea lamprey Petromyzon marinus occurs throughout North America's Great Lakes, where it has an immense economic impact on commercially and recreationally important fishes. Sea lampreys indisputably invaded Lake Erie and the upper Great Lakes from Lake Ontario in the mid-1900s, but their official status as a nonnative species in Lake Ontario is based on circumstantial evidence and has long been subject to controversy. Presently, sea lampreys are considered by U.S. and Canadian government agencies to be an invasive species within the entire Great Lakes watershed, and millions of dollars are spent annually to suppress them. We sequenced 330 base pairs of the mitochondrial DNA control region of 224 sea lampreys collected from 10 locations (3 within the Lake Ontario drainage, 2 within the Lake Superior drainage, and 5 rivers between Quebec and New York that are tributary to the Atlantic Ocean). Eighteen haplotypes were revealed, of which 17 occurred in specimens from Atlantic coast rivers, 6 in specimens from Lake Ontario, and 2 in specimens from Lake Superior tributaries. Haplotype frequencies were not significantly different (P > 0.05) within regions, indicating low or no homing fidelity. But when haplotype frequencies were grouped within regions and compared along the hypothesized colonization pathway, significant differences were seen. Pronounced differences in haplotype frequency patterns between Atlantic coast and Lake Ontario drainage collections, together with arguments against the viability of canal passage, strongly support the idea of post-Pleistocene natural colonization by one of at least three hypothesized zoogeographic pathways. If sea lampreys are indigenous to Lake Ontario, management policies aimed toward intense suppression might need reevaluation.