DULUTH -- November marks the 100th anniversary of an infamous event in the history of Great Lakes fishing: the date when sea lamprey, native to the Atlantic ocean, first moved into Lake Erie from the Welland Canal.
The parasitic invaders decimated Great Lakes fish populations, which reached rock-bottom in the mid-20th century until scientists and fisheries managers figured out how to kill lamprey in the streams where they spawn.
Since the control effort began, headed by the Great Lakes Fishery Commission in the U.S. and Canada, sea lamprey numbers have been kept in check. Their numbers are down 90% across the Great Lakes, but only with ongoing chemical applications and a $25 million annual expense.
Crews spread a specific chemical poison in 120 tributary streams across the region, rotating between streams every three or four years, to kill the lamprey larvae before they can get big and head into the lakes to start feeding on fish. Adult lamprey swim in the lake until they find a host fish to attach to, then suck the life blood out of the fish, eventually crippling and killing it.
Of the dozens of invasive species that have entered the Great Lakes over the past 100 years, none have done anywhere near the damage as sea lampreys. But none have been as well-contained, either.
Today, sport and commercial fishing across the Great Lakes “is valued at $7 billion annually, so the sea lamprey control costs, while expensive, are a small fraction of the value of the fishery,” Marc Gaden, communications director of the Great Lakes Fishery Commission, told the News Tribune.
If the effort were to stop, lamprey numbers would rebuild quickly, again decimating fish stocks in the lake within a few years, Gaden noted.
In addition to chemical control, the commission has been involved in building 75 barriers to stop lamprey from spawning, similar to the device on Wisconsin’s Bois Brule River since 1984. As long as the dams can be modified to allow fish to pass upstream, barriers work well to stop lamprey. Moreover, rivers with working barriers don’t need the chemical treatments, Gaden noted.
The Great Lakes Fishery Commission was created in 1954 by an international convention between the U.S. and Canada specifically to address the decline in fish populations. But even before then, as early as 1946, scientists looked at using chemicals to control lamprey. More than 6,000 chemicals were evaluated when, in 1956, they finally found that 3-trifluoromethyl-4-nitrophenol (TFM) killed lamprey larvae, but did not harm rainbow trout and bluegill swimming in the same test jar.
After several field trials to confirm the lab results, the first application of TFM occurred in May 1958 in what is now Elliot Creek, a Lake Huron tributary. In 1963, a second compound, 5,2-dichloro-4-nitrosalicylanilide (niclosamide), was also found to be selectively toxic to larval sea lamprey. The two chemical lampricides remain the backbone of the sea lamprey control program today.
“It’s easy to forget just how dire the viability and productivity of the Great Lakes fishery became following the sea lamprey invasion into Lake Erie and the upper lakes,” Michigan State University professor William Taylor, chair of the Great Lakes Fishery Commission, said in a statement.
Other efforts to control lamprey by fooling their sense of smell and luring them into traps are also being researched.
A long swim inland
Sea lamprey are native to the Atlantic Ocean. They first invaded the Finger Lakes of New York and Lake Ontario in the mid-1800s through human-made canals. Fishermen at the time watched the damage sea lampreys were causing in that region, but it was believed that Niagara Falls would prevent them from entering the Great Lakes. That held true until a major renovation to the Welland Canal, the artificial connection between Lakes Ontario and Erie, allowed sea lamprey to bypass the falls.
On Nov. 8, 1921, Ontario commercial fisherman Alexander Crewe was pulling nets full of lake whitefish from central Lake Erie when he noticed a lamprey much larger than the native species he was used to seeing. He sent the specimen to the University of Toronto, which confirmed it was a sea lamprey.
It took another 18 years for lamprey to reach Lake Superior and start killing lake trout here, but the invaders had a rapid impact after that. In the early 1940s, even after decades of intensive netting, commercial fishermen were harvesting nearly 400,000 pounds of lake trout annually from Minnesota waters of Lake Superior. By the early 1960s that dropped to almost nothing. The state closed the lake to netting entirely in 1962.
Lampricide treatments in Lake Superior began in 1958, but it wasn’t until the 1970s that lake trout populations began to rebound. After some ups and downs the big lake now boasts a strong sport angling trout fishery and ongoing commercial fishing in some areas. Lake trout have rebounded so well in Minnesota waters of the lake that the state Department of Natural Resources says stocking is no longer necessary.
It’s not that lamprey have been eliminated. Their pre-control numbers were estimated at 780,000 adult lamprey in Lake Superior back in the 1950s. That’s been reduced by 76% to an estimated 184,000 lamprey in the lake today. The Great Lakes Fishery Commission hopes to trim that number down to about 48,000. Lamprey numbers are down 93% in Lakes Michigan and Ontario, 84% in Lake Huron and 50% in Lake Erie.
“Today, sea lamprey control in the Great Lakes is remarkably successful,” said commission Vice Chair James McKane, of Kitchener, Ontario. “Over the past six and a half decades, the Great Lakes Fishery Commission and its partners have reduced sea lamprey populations by 90% in most areas. … Without sea lamprey control, the $7 billion fishery would cease to exist.”
John Myers reports on the outdoors, environment and natural resources for the Duluth News Tribune. He can be reached at firstname.lastname@example.org.