
Chronicle
by Bert Bowers
Control
is the Name of the Game
Winning the War Against the Sea Lamprey
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.