The sea lamprey is one of the few aquatic invasive species that is being successfully controlled. In the late 1940s the State of Michigan began investigations into the biology of sea lampreys. In 1950, this became a federal program. In 1955, the Great Lakes Fishery Commission (GLFC) was created under a convention between the United States and Canada for the purpose of restoring fisheries. One of the GLFC’s primary duties was the control or eradication of sea lampreys. It currently manages sea lamprey populations across the Great Lakes to about 10% of their former levels. Control is delivered through its control agents, the U.S. Fish and Wildlife Service and the Department of Fisheries and Oceans, Canada.
Control depends on breaking the life cycle. The first control efforts attempted to do that by blocking access to the spawning areas in streams. This was only partially successful because the weirs used to do this were impossible to maintain 100% of the time. There were attempts to use electric fields alone or in conjunction with the weirs, but that was eventually abandoned as too dangerous. A second vulnerable point in the life cycle is during the larval stage, when sea lampreys spend at least three years burrowed in the stream sediment. During the 1950s, over 6,000 chemicals were screened before finding one that was selectively toxic to sea lampreys. That chemical, TFM, has been carefully applied to infested streams, beginning in Lake Superior in 1958. Treatments quickly decreased sea lamprey numbers to 10% or less of their former numbers. Reduced lamprey numbers allowed native and stocked lake trout to survive and the lake trout populations to rebound. Recently, the restoration of lake trout in Lake Superior was declared a success and federal stocking of lake trout was stopped. Lake trout stocks in Lake Superior are once again selfsustaining.
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| Locations of dams preventing the spread of spawning sea lamprey. |
Treatments with TFM start with electrofishing surveys of the Great Lakes tributaries known to potentially produce sea lampreys. Based on estimates of the number of metamorphosed sea lampreys to be produced and on treatment costs, a list of streams to be treated is made each year. Because of the duration of the larval stage, streams are treated at intervals of 3 to 5 years or longer.
Ineffective and labor-intensive screen weirs have been replaced with low-head barriers that block sea lampreys but allow jumping fish to pass. A combined low-head and electrical barrier was constructed on the Ocqueoc River, which functions effectively as a low-head barrier but also blocks sea lampreys during high water on this flood-prone stream. This combination of proven technologies allows effective blockage of migrating sea lampreys and passage of jumping fishes under a much broader range of stream flows. Under normal flows, the low-head barrier is functional, no current flows to the electrical barrier, and jumping fish can pass. During flood conditions, when the low-head barrier is inundated, the electric barrier automatically turns on and blocks sea lampreys.
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