Sea lampreys (Petromyzon marinus) are primitive, jawless fish that are parasitic to other fishes during their adult life stage. They use an oral disk to attach to larger fish and sharp teeth to rasp through the scales and skin of host fishes to feed on their body fluids. Massive fluid loss and infections at the wound site often result in death to the host fish. During its life as a parasite, each sea lamprey can kill the equivalent of 40 or more pounds of fish.

Sea lampreys are native to the Atlantic Ocean and ascend streams and rivers to spawn. They were first found in Lake Erie in 1921, after traveling through the Welland Canal. From Lake Erie, sea lampreys invaded the three remaining Great Lakes. By the 1940s, sea lampreys were abundant in all of the upper Great Lakes, contributing to severe reductions in the lake trout, whitefish, and cisco populations. Commercial catches of lake trout from Lakes Superior and Huron declined from 4.5 million pounds annually before sea lampreys invaded to about only 300 thousand pounds annually in the early 1960s. Motivated by the resulting collapse of commercial fisheries in the Great Lakes, the governments of the United States and Canada created the Great Lakes Fishery Commission by bilateral agreement in 1955 to protect the fisheries resources of the Great Lakes Basin.

Because larval sea lampreys remain burrowed in the sediments of streams and rivers for 4-7 years, the control program focused on this life stage. A program was begun to identify a chemical that could be used to control larval sea lamprey. In the process of screening more than 6,000 chemicals during the 1950s, U.S. Fish and Wildlife Service scientists discovered the compound TFM (3-trifluoromethyl-4-nitrophenol), which demonstrated significant selectivity in killing sea lampreys without affecting other aquatic organisms. A chemical control program based on TFM had begun. Since that time, another lampricide, niclosamide (2',5-dichloro-4'-nitrosalycylanilide), was also identified, followed by the development of a number of specialized formulations of both chemicals. Of the 5,747 streams and tributaries of the Great Lakes, about 250 are chemically treated on a 3-5 year cycle.

An aggressive and far reaching research program by U.S. Geological Survey scientists at the Upper Midwest Environmental Sciences Center (UMESC) in La Crosse, Wisconsin, is designed to provide technical assistance to U.S. and Canadian sea lamprey control biologists. Scientists at the UMESC work closely with colleagues in the U.S. Fish and Wildlife Service and the Canadian Department of Fisheries and Oceans to develop specialized formulations of lampricides and application strategies to maximize lampricide impacts to larval sea lamprey communities while minimizing treatment effects to native fauna.

The sea lamprey control and research programs of the Great Lakes Fishery Commission and its agents, the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and the Canadian Department of Fisheries and Oceans, have been highly successful in revitalizing the Great Lakes commercial and sport fisheries. Chemical control continues to play an integral role in limiting the sea lamprey populations in the Great Lakes.

Lake trout populations in Lake Superior, already in decline from overfishing and environmental problems, were decimated by the sea lamprey invasion. Initiation of the sea lamprey control program resulted in a quick decline in the numbers of sea lamprey and allowed some recovery in the numbers of lake trout in Lake Superior.

Reports

• Boogaard, M.A., C.S. Kolar, and D.L. Waller. 2004. Acute toxicity of 3-triflouromethyl-4-nitrophenol (TFM) and a TFM-1% niclosamide mixture to the giant floater (Pyganodon grandis), fragile papershell (Leptodea fragilis), and pink heelsplitter (Potamilus alatus) unionid mussels and sea lamprey (Petromyzon marinus) larvae. Completion report submitted to the Lake Champlain Fish and Wildlife Management Cooperative and the Great Lakes Fishery Commission. 21 pp.