From Catastrophe to Recovery: Stories of Fishery Management Success

Restoration of Anadromous Sea Lamprey to the Connecticut River and Adjacent Watersheds

Stephen R. Gephard


Abstract.—Anadromous Sea Lamprey Petromyzon marinus spawning runs in the Connecticut River and other streams in the state of Connecticut, USA were decimated by the construction of dams, which were built from 1720 to 1920 for a variety of reasons, notably hydropower. Many of these dams blocked migratory routes to spawning grounds. Government fish management programs begun in the 1960s and 1970s to restore other anadromous species to the Connecticut River did not initially target Sea Lamprey for restoration. The installation of fishways intended for Atlantic Salmon Salmo salar and American Shad Alosa sapidissima at barrier dams resulted in coincidental upstream passage of Sea Lamprey. The public knew about the destructive invasion by Sea Lamprey into the Great Lakes and initially questioned the wisdom of letting Sea Lamprey move upstream into areas where they were not present. The Connecticut Department of Energy and Environmental Protection (CTDEEP) engaged in a public education campaign to inform about the benefits of Sea Lamprey restoration, which include increased biodiversity and forage base for other fish species, importation of marine-derived nutrients into the freshwater ecosystems, and beneficial physical habitat modification through nest building. By the 1990s, the species was officially targeted for restoration, reflecting evolving public perceptions and state agencies’ embrace of increased biodiversity as a program goal. The CTDEEP pursued Sea Lamprey restoration in other watersheds in addition to the Connecticut River watershed. The main strategies for restoration have been provision of fish passage, transplantation, and public education. Restoration efforts have succeeded in increasing the number of adult Sea Lampreys in specific watersheds and expanding their geographical range within these watersheds. Monitoring and research have advanced our knowledge of anadromous Sea Lamprey, including details of the juvenile and adult migrations. Results in Connecticut suggest that individual Sea Lampreys will move upstream beyond any pheromone signal when the run has been previously established in that river below the dam, but they tend not to enter a river from the ocean without a pheromone signal. Many reasons exist why Sea Lamprey runs expanded into vacant habitat more quickly than other anadromous species, but the fact that Sea Lampreys do not home to natal rivers has limited the subsequent increase of the Connecticut River annual run. Lessons learned include specific tools for restoring Sea Lamprey, how to combat negative public perceptions of a parasitic animal, and how to promote support for restoring runs of ecologically valuable but uncharismatic species.