The Importance of Dams to Sea Lamprey Control in the Great Lakes

The Great Lakes Fishery Commission implements a program to control the invasive, parasitic sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes.  The primary method of control is periodic applications of selective pesticides (lampricides) that kill larval sea lampreys in their natal tributaries.  Equally important is the use of barriers to prevent adult sea lamprey from accessing hundreds of Great Lakes tributaries suitable for spawning.  Low-head barriers built specifically to block adult sea lampreys are operated in about 70 tributaries around the Great Lakes. Seasonal barriers have been implemented, but are less effective than permanent low-head barriers.  Dams built for other purposes, however, also restrict the spawning success of sea lampreys and are crucial to the control program.  Removal of these dams will (i) increase habitat available to spawning sea lamprey, (ii) risk increases in the abundances of parasitic, juvenile sea lampreys in the lakes, and, (iii) risk elevating the demand and cost of lampricide treatments to the point of being unfeasible.  A basin-wide dam removal strategy is needed to ensure that removal decisions balance the use of dams for sea lamprey control and removal of dams to restore valued riverine fishes and habitat.