Sea lampreys causing havoc on fishery
By Kevin Naze
Green Bay Press-Gazette
Posted online July 14, 2005
A multi-million-dollar fight against an enemy that kills
more trout and salmon than sport, commercial and tribal
fishers combined continues more than 40 years after it
Sport anglers concerned over few lake trout in the catch
in recent years and increased sightings of sea lampreys
on salmon have a good reason to be: According to the Great
Lakes Fishery Commission, the number of lamprey spawners
in Lake Michigan has tripled in the past decade to somewhere
between 150,000 and 200,000 spawners.
“It is obvious there are more lampreys in Lake Michigan
than at any time since (after) the initiation of control
efforts,” said Mark Holey, project leader for the U.S.
Fish & Wildlife Service’s Green Bay Fishery Resources
The lamprey, an eel-like invader that latches on to fish
with an oral disc, sharp teeth and a grasping tongue,
threatens a sport and commercial fishery worth an estimated
$4 billion to $5 billion.
Holey said it is believed the primary cause for the increase
is a faulty dam with holes big enough for lamprey to get
through on the Manistique River in Michigan’s Upper Peninsula.
“Actually, the initial increase was thought to have come
from the St. Mary’s River, between lakes Superior and
Huron,” Holey said. “However, once that river was treated,
it was apparent the lamprey numbers in Lake Michigan were
Holey said the Manistique — the largest watershed in
the U.P. — is a difficult river system to treat, with
few barriers once lampreys get above the first dam.
In response to high marking rates on Great Lakes fish,
the Fishery Commission treated the Manistique in 2003
and 2004 which should produce noticeable results in lake
trout numbers by 2006, Holey said.
“It just goes to show how fragile the fishery that anglers
enjoy and rely on really is to lamprey predation, one
of the original invasive species,” Holey said. “The entire
balance of the Great Lakes fisheries would change dramatically
should lamprey control be relaxed or not adapt to new
challenges. It also illustrates how important it is to
keep new invasive species out of the Great Lakes at all
Early this month, sport troller and tournament angler
Michael Collins of McFarland had already reeled in five
salmon with lampreys attached two at Racine, two at Algoma
and one at Milwaukee. Many other fish have had scars resulting
from run-ins with the parasitic predators.
“I’ve been fishing Lake Michigan for over 20 years and
have never seen as many salmon with lamprey marks,” said
Collins, a past member of the Lake Michigan Fisheries
Forum, an advisory group to the Department of Natural
Through the years, very few lampreys stayed attached
on fish he had hooked, he said.
“Each of my last three trips I have had fish with lampreys
still on, and that clearly represents a drastic change
that threatens our fishery,” Collins said after an outing
at Algoma July 2.
Before chemical treatments began in 1958 in Lake Superior
streams and 1960 in Lake Michigan, lampreys devastated
a fishery already sliding from overharvest by commercial
netters. Lake trout production in Lake Michigan dropped
from 7 million pounds annually to zero, and populations
in the remaining lakes were reduced to small remnants
of historic levels.
During the 1950s, scientists tested almost 6,000 compounds
to identify one to which larval sea lampreys were especially
sensitive. The resulting discovery of the lampricide known
as TFM was effective enough that biologists believe the
population was cut by 90 percent.
The never-ending battle to continue international funding
for the war on lampreys has taken many twists and turns,
ranging from a reduction in lampricide use to an increase
in electrical and low-head barriers, traps and the release
of sterilized males.
Between them, the U.S. and Canada spent close to $100
million in the 1990s alone in an effort to control sea
Lampreys are most vulnerable during their worm-like larval
stage, when they burrow in the sand or silt bottoms of
Great Lakes tributaries for three to seven years or more.
As adults, they spend 12 to 20 months in the lake, killing
an estimated 20 to 40 pounds of fish each before returning
to rivers to spawn and die.
Like most exotic invaders, lampreys have no natural predators.
A native to the North Atlantic Ocean and many of its tributaries,
they were discovered in Lake Ontario around 1835, then
Lake Erie in 1921, Lake Huron in 1932, Lake Michigan in
1936 and Lake Superior in 1946.
Niagara Falls had served as a natural barrier until the
construction of the Welland Canal in 1829 for the shipping
Spawning typically occurs in late spring or early summer,
and one female can produce 60,000 eggs. Biologists estimate
about 14 percent of them are likely to be deposited in
the nest, and once there, they have about a 90 percent
chance of survival.
Great Lakes anglers, an estimated 800,000 of them, are
the biggest beneficiaries of sea lamprey control, and
many believe it’s only a matter of time before they’ll
be asked to contribute directly to the multi-million dollar