The Role of the Champlain Canal and Erie Canal as Putative Corridors for Colonization of Lake Champlain and Lake Ontario by Sea Lampreys

The origin of populations of the landlocked Sea Lamprey Petromyzon marinus in Lakes Champlain and Ontario, whether by artificial canals or by natural colonization following the last ice age, is controversial, in part because the related history and ecology had been poorly documented. This situation favored a native classification for the populations in both lakes based mainly on genetics. A native classification for the Lake Champlain population was predicated on either of two erroneous dates of first record, 1841 and 1894, whereas the correct date, 1929, was much more recent and strongly supports a nonnative classification. The detection of the Sea Lamprey in Lake Champlain occurred shortly after the opening in 1916 of the Champlain Barge Canal, which opened the upper Hudson River to fish passage. The case for a native Lake Ontario population did not account for a watershed breach in 1863 between the Susquehanna River, where the Sea Lamprey had been common, and the Lake Ontario drainage. Shortly after this canal-related connection was made, Sea Lamprey populations became abundant, nearly simultaneously, in four locations in the Lake Ontario drainage, suggesting this breach was the entry point for the founding population. The genetic distances between the landlocked populations and the Atlantic Ocean population appear to have been caused by recent bottlenecks rather than long-term residence; a recent genetic bottleneck was detected in the Lake Ontario population. Native classifications rested, in part, on extraordinary ecological scenarios, whereas nonnative classifications are consistent with experience in the upper Great Lakes and with well-known vectors of range expansion (canals, dam openings, watershed breaches). These findings in aggregate favor a nonnative classification of the Sea Lamprey in both lakes. Received November 7, 2013; accepted December 16, 2013