History of and Advances in Barriers as an Alternative Method to Suppress Sea Lampreys in the Great Lakes

The Great Lakes Fishery Commission (GLFC) continues to seek additional methods of sea lamprey ( Petromyzon marinus) control to reduce reliance on chemical lampricides (pesticides) and increase the efficiency of the program. Barriers to migrating sea lampreys in tributaries can significantly reduce the spawning potential of sea lamprey in the Great Lakes. These barriers can be any natural or man-made structure that restricts the access of migrating sea lampreys to spawning habitat in streams. During the past four decades, the GLFC recognized a greater need to maintain current barriers to sea lamprey spawning migration and develop new, less intrusive devices to enhance the integrated sea lamprey control program. The “standard” sea lamprey barrier uses a fixed-crest height and overhanging lip to maintain a vertical drop of about 30 cm from headwater to tailwater over the period of lamprey migration. Although most sea lamprey barriers are of fixed-crest design, alternative designs (i.e., electrical, adjustable-crest, velocity, and combined fixed-crest and electrical barriers) have been built and are being tested. Between 1958 and 1999, 61 barriers of various design have been modified or installed in Great Lakes streams. The GLFC plans to add to the 61 current barriers by building additional barriers on 90 candidate streams (Lake Superior, 10; Lake Michigan, 24; Lake Huron, 23; Lake Erie, 3; Lake Ontario, 24). As we seek to expand the role of barriers in sea lamprey management, we must remain vigilant to the hundreds of existing dams known to limit stream habitat available to sea lampreys. The current movement toward dam removal and fishway construction without regard to sea lampreys could result in additional habitat becoming available to sea lampreys. The loss of one or two large dams could easily overshadow the gains made through all the purpose-built sea lamprey barriers to date.