Controlling the Noxious Sea Lamprey on the Great Lakes

By Terry Hubert, Cindy Kolar, Jane Rivera, and Mike Boogaard

From April through October each year, personnel of the sea lamprey control units of the U.S. Fish and Wildlife Service (FWS) and the Department of Fisheries and Oceans-Canada (DFO) head into remote areas along streams and rivers in the Great Lakes basin. Facing harsh weather, bugs, and an occasional bear, their mission is to locate and kill as many sea lamprey (Petromyzon marinus) larvae as possible. The effort is part of a successful binational program to control this destructive Great Lakes invader. The ability of the control agents to carry out their mission has, in large measure, been due to the efforts of scientists at the USGS Upper Midwest Environmental Sciences Center in La Crosse, WI, and the USGS Great Lakes Science Center in Ann Arbor, MI. For over 60 years, these laboratories have supported a pest management program that is a model for the world.

Abundance of lake trout (1930-1996, no data collected in 1966) and sea lamprey (1956-1996) in Lake Superior. Lake trout were declining significantly before control of sea lampreys began in the early 1960s (from the Great Lakes Fishery Commission).

Why control sea lampreys?
Sea lampreys are primitive fish that as adults are parasitic to other fishes. The mouth of a sea lamprey is a suction disc with many rows of teeth that lock on to prey. Once attached, the lamprey uses its file-like tongue to bore a hole into the host to ingest blood and body fluids. During its parasitic stage, each sea lamprey can kill up to 40 pounds of fish. Larval sea lampreys live in stream sediments for several years before they transform into adults and migrate to the Great Lakes. There they grow rapidly by preying on large fishes before returning to streams to spawn.

The mouth of the sea lamprey (left), showing the numerous teeth. Sea lampreys cling to fish by suction (center) and then use their boney, rasping tongue to bore into the flesh, causing significant damage and death to fish like lake trout (right). (photo credits: left - GLFC; center - FWS; right - USGS).

Modifications to the Welland Canal in 1919 provided sea lampreys access to the upper Great Lakes. By the 1940s, sea lampreys were abundant in all of the lakes and contributed to the extinction or severe reduction of lake trout, whitefish, and cisco. By the early 1960s, commercial catch of lake trout in Lake Superior declined from about 15 million pounds to around 300,000 pounds. Although poorly regulated commercial fishing played a role in the decline, the invasion of the sea lamprey triggered the collapse. Without sea lamprey control, we simply would not have a viable fishery in the Great Lakes.

The dawn of sea lamprey control
In 1946, Congress directed the FWS to develop methods of controlling sea lamprey. In 1954, the United States and Canada, realizing that reestablishing the Great Lakes fishery would require the effort of both countries, signed an agreement from which the Great Lakes Fishery Commission (GLFC) was formed. In addition to leading fisheries research and overseeing the general health of the Great Lakes, the GLFC was specifically charged with eradicating sea lamprey from the lakes.

Early control relied on barriers to prevent sea lampreys from spawning in streams. This technique had limited effectiveness, and in 1951 researchers looked to chemical control. During the next 7 years, researchers at the Hammond Bay Biological Station in Millersburg, MI, tested almost 6,000 chemicals before a compound was discovered that was selectively toxic to sea lampreys. Several years later, a second compound was discovered. These two lampricides, TFM and niclosamide, helped the control program drastically reduce sea lamprey populations, which allowed the recovery of fish stocks worth $2-4 billion annually to the economies of the Great Lakes states and Canadian provinces. Today, sea lampreys have been reduced by an astounding 90 percent in most of the Great Lakes, making this program one of history's best examples of environmental damage mitigation. The continued use of lampricides ensures that sea lamprey populations will be kept at acceptable levels.

Targeted treatment of the St. Mary's River with BayluscideŽ 3.2% Granular Sea Lamprey Larvicide in 1998 and 1999. The granular formulation (left) eliminated the occurrence of fine dust, which represented a hazard to applicators. Staff at Hammond Bay Biological Station surveyed and ranked 112,000 sites to determine treatment priority (center). The application was done by helicopter guided by GPS (right).

Technical assistance program
USGS scientists have worked closely with FWS and DFO staffs in a long-standing partnership to implement the control program. Researchers successfully improved treatment models and lampricide formulations. These improvements maintained treatment effectiveness while using less chemical, and reduced effects to non-target species. For example, scientists determined that pH and alkalinity of streams greatly affect lampricide toxicity. They used this knowledge to develop and supply treatment managers with models based on these parameters. The result was a significant reduction in the amount of chemical applied. The reduction in chemical usage saves the sea lamprey program more than $1 million annually and significantly lowers the risk to non-target aquatic species, while maintaining levels of sea lamprey control.

USGS scientist conducts a toxicity test to determine what concentrations of the lampricides may be applied to kill lamprey without harming non-target species. One series of experiments was used to develop new treatment guidelines for treating streams containing lake sturgeon, a species sensitive to lampricides.

USGS scientists invented lampricide formulations that more effectively target larvae and are safer to apply, and adopted new approaches for selecting areas to be treated. An innovative bottom-release granular formulation of niclosamide allows treatment in areas where traditional application methods are impractical. One area treated was the St. Marys River, a large river system that connects Lake Superior and Lake Huron. Because conventional treatment with TFM was costly, the system went untreated for many years and became the largest producer of sea lampreys on Lake Huron. In 1998 and 1999, areas of the river where larvae were concentrated were treated with granular niclosamide, and 85 percent of the larvae were removed. Following those treatments, the attack rate on lake trout in Lake Huron dropped sharply and is now approaching acceptable levels, allowing the recovery of the Lake Huron fishery. Researchers at USGS continue work to improve the effectiveness of lampricide stream treatments, and conduct studies on alternative methods of sea lamprey control to reduce our reliance on chemical applications. These research efforts are continuing to enhance the health of the Great Lakes fishery and protect the economic well-being of the many recreational and commercial fishers who depend on this ecosystem.

UMESC scientists place cages of fish into the Ford River just prior to application of TFM by Fish and Wildlife Service personnel. Muscle tissue of the fish was examined for residues of TFM to determine the concentrations of the chemical present in fish following a treatment.