The parasitic sea lamprey, one of the earliest exotic species accidentally introduced into the Great Lakes via man-made canal systems, created a problem that was recognized early on by people in the fisheries business. Beginning in the lower lakes in the 1930s and ’40s and reaching Lake Superior by the 1940s and ’50s, the lamprey problem turned into a disaster as one commercial fishery after another crashed.

In those early days, states and provinces were economically and technically unable to cope with the problem. For this reason, the United States Fish and Wildlife Service (USFWS) and its Canadian counterpart, the Department of Oceans and Fishes, were asked to look into the problem. It was decided by research biologists to concentrate control efforts on Lake Superior, since there was still a viable native lake trout fishery to be saved. Lake trout had been virtually wiped out in the lower Great Lakes by this time.

In the late 1940s, the various agencies concerned declared war on the sea lamprey. After nearly 50 years and many battles, the war still rages. It is fought quietly, for the most part, in many of the backwater areas of the Great Lakes - places like Michigan’s Two-Hearted River, Wisconsin’s Bad River, Ontario’s Batchawana River and other optimum sea lamprey-producing tributaries.

An early attempt to bring the lamprey population under control on Lake Superior tributaries was initiated on streams where sea lamprey were known to spawn, using electro-mechanical barriers called weirs. (I joined the USFWS in September, 1953, as a lad of 19 years and worked in this effort until retirement in 1988.) By 1956, all the known sea lamprey-producing streams in the United States and Canada on Lake Superior were blocked with the electrical barriers.

Preliminary studies showed that the adult parasitic sea lamprey spends 12 to 18 months in the Great Lakes, then migrates up a desirable stream to spawn and die.

The damage wreaked on Lake Superior’s native fish species
is obvious in the circular wounds and scars left by lamprey.

The female lamprey produces about 65,000 eggs. The eggs hatch in the stream and the young larval lampreys, called ammocetes, burrow into the stream bed, where they spend three to seven years or more. During this phase of their life cycle, they are not parasitic to fish, feeding only on microorganisms.

After this phase, the animal transforms into a parasitic adult, leaves the stream bed and migrates to the lake to feed on fish for the next several months. Research has shown that a lamprey will consume about 40 pounds of fish to reach the breeding stage. Its favorite prey in Great Lakes waters appears to be lake trout. The following spring, adults swim back upstream to spawn, completing the life cycle.

In the beginning, the electrical weir was the only method of control available, but it could prevent spawning of only one generation of lampreys at a time and only if it worked 100 percent of the time, which was rare. If a barrier failed just during one night at the peak of a spawning run, a whole year’s class of lamprey was introduced into that particular stream. Since the weirs were electro-mechanical devices, there was plenty of room for failure.

At the same time control was being attempted by weirs, a more desirable tool was being researched. It was envisioned to be a chemical to kill lampreys, yet be harmless to non-target species in the streams. If such a chemical could be found and methods of using it in flowing waters could be developed, it would wipe out several generations of the parasite in one treatment. To this end, the USFWS set up a bio-assay laboratory in the late 1940s at an abandoned Coast Guard station in Hammond Bay, Michigan, and began testing chemical compounds.

As early as 1956, all known sea lamprey-producing streams were blocked with electro-mechanical weirs.

Around 1958, after testing more than 5,000 compounds, the chemical Tri-Flouro-Methyl-Phenol (TFM) was found to fit all the requirements. It worked well in the lab and, after being field tested in small streams, it looked even better. TFM is an organic compound that is water soluble and, in a relatively short period, breaks down to harmless residuals. The chemical is registered with the Environmental Protection Agency.

The use of TFM brought the lamprey’s population under control in the early 1960s on Lake Superior and control swiftly followed on lakes Michigan and Huron. Numbers of spawning lampreys at the weirs were reduced by 90 percent by 1960.

Efforts in those early days were aimed at saving the commercial fisheries, an enterprise that supplied around 2,000 metric tons of lake trout annually from Lake Superior alone through the 1930s and ’40s. These fish harvests were reduced to a trickle through the late 1940s to ’60s and commercial fishing was almost completely eliminated by the various agencies involved.

Because of the management controls that were tried, native trout stocks in Lake Superior survived these lean years. A self-sustaining population is thriving in many areas of the lake today. According to an April 1996 news release from the Great Lakes Fisheries Commission, in some areas of Lake Superior populations are back to 80 percent of those that occurred before invasion of the sea lamprey.

Another positive result of lamprey control and fisheries management is the booming sport fishery in all of the Great Lakes. This activity brings about $2 billion annually into the state of Michigan alone.

Dr. Gary Klar is Field Supervisory Biologist at the USFWS Biological Station in Marquette, Michigan, and oversees sea lamprey control operations throughout the Great Lakes.

Unpleasant as it may be, this picture is still a fact of life in Lake Superior’s fishery.

“At present, we have about 90 percent control on sea lamprey populations in Lake Superior, which means that the lake should sustain lake trout levels at about 80 percent of the lake’s potential,” Dr. Klar says. “This is, of course, at present funding levels. If budget cuts are made, control will be cut back and fish populations must suffer.”

Still, many environmentalists are uneasy about the introduction of chemicals into the environment and TFM is the primary means of controlling the lamprey at this time. It is the hope of the agencies using the chemical to be able to reduce the use of TFM to 50 percent by the year 2000.

When queried about this possibility, Dr. Klar says, “To this end, we have already cut back on our use of TFM by 20 to 30 percent.”

Ongoing research to test the efficacy of introducing sterile males into spawning streams is under way and shows some promise as a supplemental control to the chemical treatments. Newer, more technically sophisticated electrical weirs are also being studied and appear to be of some use. Along that line, mechanical barrier dams have been installed in streams such as the Misery and Whitefish rivers in Michigan and the Brule and Iron rivers in Wisconsin and show limited success. As with all research projects, none of these is without problems, but diligence and perseverance continue to win battles, if not the war.

A native of Big Bay, Michigan, and a captain of charter boats from Marquette and Munising, Michigan, during warm weather months, Albert Bowers spent his adult life battling lampreys out of Marquette. He became interested in writing upon retirement from the USFWS and has produced a number of published articles, one of which appeared in the April/May 1996 issue of this magazine.

The research vessel (RV) Grayling is one of several ships operated by the National Biological Service (NBS), an arm of the U.S. Fish and Wildlife Service. Its home port is Cheboygan on Lake Michigan and it is usually at work on lakes Huron and Michigan. Once a year, however, the vessel makes a trip to the eastern end of Lake Superior to collect scientific data on a variety of topics.

Since forage fish like sculpin, stickleback, smelt, shiners and other species are the food supply for fish species higher in the food chain, the scientists of the NBS are keeping particular tabs on the biological condition of these forage species. The condition of certain forage species may also indicate other stresses like predation by the sea lamprey or pollution - perhaps even identifying certain kinds of pollution. They are not easily studied though, preferring to stay close to the bottom for protection during daylight.

Information collected over a period of many years is valuable in a variety of ways and can indicate trends influencing management decisions. It is the mission of the research scientists to keep a watchful eye on the Great Lakes ecology and make data available when decisions are needed regarding the fishery.

Management tools like fish quotas, size of nets, where nets can be set and at what depths come directly out of such data. Sport fisheries decisions like numbers for a catch, size limits, how many lines can be fished and what areas may be off limits are also based on data collected by scientists on vessels like the Grayling.