The Great Sea Lamprey Fiasco
Once heralded as the "greatest invasive species control success story" for its perceived role in restoring the collapsed Great Lakes fishery, scientists are now implicating the US Fish and Wildlife Service's use of the chemical lampricide TFM in the mass deaths of native species from mussels to mudpuppies. Environmental activists and ecologists are calling for an end to TFM treatments in favor of alternative sea lamprey controls.
The Sea Lamprey
Native to the Atlantic Ocean, sea lampreys were first recorded in the upper Great Lakes in the 1920s, following the construction of the Welland Canal which bypassed their natural barrier, Niagara Falls. The sea lamprey’s elongate and slimy body may look eel-like, but it belongs to a much older group of jawless fish which first appeared 360 million years ago. During their first three to ten years of life, sea lamprey larvae (called ammocetes) filter feed in river sediment.
Following a mysterious trigger, they burst into the water column, develop beady eyes, a suction cup mouth filled with rows of sharp teeth, and a rasping tongue. Then, they travel downstream to the Great Lakes where they spend the next twelve to eighteen months feeding off the blood and body fluids of native fish species.
Prior to sea lamprey invasion, the United States and Canada fisheries were estimated to harvest 15 million pounds of lake trout (Salvelinus namaycush) every year. By the 1960s, harvests had declined by 98%. The coinciding boom in the sea lamprey population was seen as a smoking gun, and the species was widely blamed for the fishery’s collapse.
A Treaty is Signed
A treaty between the United States and Canada established the Great Lakes Fisheries Commission in 1954 with the primary goal of eradicating sea lamprey populations. In 1958, it was discovered that 3-trifluoromethyl-4-nitrophenol or TFM is highly toxic to sea lamprey while being less toxic to non-target organisms at the same concentrations. Exposure to TFM starves a sea lamprey’s cells of energy and rapidly leads to death.
Today, the US Fish and Wildlife Service and Fisheries and Oceans Canada partner with the Great Lakes Fisheries Commission to apply TFM to approximately 500 Great Lakes tributaries on a three-to-five-year basis. The use of TFM is credited with the recovery of game fish populations as well as a 90% reduction in the population of sea lampreys. “It [TFM] really is miraculous,” says Marc Gaden, the communications director and legislative liaison for the Fisheries Commission. “We would give anything to have something even half as good for Asian carp, zebra mussels, or round gobies.”
Proponents of TFM praise its apparent selective toxicity for sea lampreys. While he admits non-target mortality does occur, its “extremely rare,” says Marc Gaden. Researchers monitoring the immediate aftermath of TFM treatments tell a different story, however.
Dr. Tim Matson
Every summer for the last thirty years, Dr. Timothy Matson has returned to a thin strip of gravel in the middle of Ohio’s Grand River just below Lake Erie’s central basin. Even in his first year of retirement after forty-five years as Curator of Vertebrate Zoology at the Cleveland Museum of Natural History, Matson’s research hasn’t slowed down in the slightest. The 60-something-year-old stands tall and thin, knees locked together like a toy soldier. With his neatly combed, gray hair and mustache, blue collared shirt, and matching slacks, he looks more prepared to deliver a lecture than to wade chest deep into the nearest river.
Matson’s obsession with TFM first began in 1987, when the US Fish and Wildlife Service treated Conneaut Creek, a nearby tributary, for the first time. “There was so much mortality,” Tim says, and he has the jars of preserved specimens to prove it. “TFM doesn’t just kill lampreys, it kills everything.”
The Mudpuppy Salamander
One species that may be as susceptible to TFM as the sea lamprey is the mudpuppy salamander (Necturus maculosus). Unlike other amphibians, which start their lives in water and later metamorphose and move onto land, mudpuppies never metamorphose and never leave the water. Instead, they grow to maturity (reaching two feet or more in length) retaining their external gills, a feature normally lost in adult salamanders. The mudpuppy’s fully aquatic life, nocturnal habits, and tendency to hide under large, flat rocks on the riverbed, means they are rarely seen.
In the spring of 2009, the USFWS applied TFM to the Lamoille River in Vermont for the first time. Post-treatment mortality surveys found 500 dead mudpuppies in just 5% of the treated area. Mortality events like this are not uncommon.
In their permit to treat the Lamoille, the USFWS states “mudpuppy mortality is expected, but we do not expect population level effects.” Tim Matson is soft spoken, but when the topic turns to the USFWS’s treatment of mudpuppies, he has some choice words. “They don’t know anything about the [mudpuppy] populations,” he says, the frustration audible in his voice. In 1990, he published a study that showed a 29% decline in Ohio’s Grand River mudpuppy population following the application of TFM. In his study, he suggested that four applications of TFM within twelve to twenty years could result in population declines of 75%.
“It was like a deep horror,” says Ira Powsner, an environmental activist who witnessed a repeat treatment of the Lamoille in 2021. “It’s like, wow, this is a real environmental catastrophe.”
During that repeat treatment, Powsner organized a group of amphibian-friendly environmental activists to protest on the Lamoille.The protest had just one goal, to spare the Lamoille River of lampricide treatments. “I thought that not treating one river with lampricides might be politically winnable,” says Jim Andrews, a Herpetologist with the Vermont Reptile and Amphibian Advisory Group. “I was incorrect.”
Image by Ira Powsner
Those in favor of lampricides say that without repeated applications of TFM wherever sea lampreys remain, tributaries like the Grand and Lamoille River would quickly become breeding grounds for sea lamprey and offset the progress that has been made to control them. “They [sea lampreys] have great spawning potential, lots of food to eat, and nothing keeping them in check,” says Marc Gaden with the Fisheries Commission. “When uncontrolled, [sea lampreys] just knock the stuffing out of the fish in the lake.”
Volunteers representing federal and state resource agencies, universities, museums, county metroparks, and private citizens, work together to collect non-target organisms killed in the treatment.
During the 2017 treatment of the Grand River, 3,057 non-target species were collected dead for just nine dead sea lampreys. Among the deceased included several species of darters, catfish, minnows, sunfish, suckers, amphibians (including mudpuppies), as well as protected native lamprey species. Other organisms that have been reported dead following treatments include trout, perch, logperch, suckers, salmon, bullheads, channel catfish, gar, mudminnows, lake sturgeon, macroinvertebrates, and mussels.
Like mudpuppies, stonecats are one of the most susceptible species to TFM. “We had garbage bags full,” Matson recalls.
300 non-target organisms are killed for every one sea lamprey
Recent research is poking holes in the long-held belief that sea lampreys are responsible for the demise of game fish like lake trout. A study published in Environmental Science and Technology in 2003, revealed another lake trout killer, one even more insidious and destructive than the sea lamprey. The study found that the chemical dioxin is lethal to lake trout at concentrations of just 30 parts per trillion (one drop in 500,000 gallons of water). Dioxins are byproducts of industrial and municipal waste and are 200 times more deadly than DDT. Peak production of these highly toxic chemicals in the middle of the 20th century coincides perfectly with the decline of lake trout. From 1950 to 1975, dioxin levels in the Great Lakes were above 100 parts per trillion, meaning that larval lake trout mortality was 100% for over 20 years.
“The toxicity alone explains what happened,” said the late Philip Cook, the lead author on the study, in an interview with the Washington Post. “It wouldn’t even matter if there were sea lamprey or overfishing.
While TFM is effective at controlling sea lampreys, it is not the only method available. Nick Johnson, a research ecologist with the United States Geological Survey at Hammond Bay Biological Station in Michigan, is working to identify potential supplemental controls. “We are the research and development side of the lamprey control program,” he says. His work includes using pheromones to draw adult lampreys into traps and alarm cues to repel them from suitable spawning habitat.
He also oversees a sterilized male release program that has been underway since the 1970s. Captured males are chemically sterilized and then returned to their tributaries. As adults, lampreys no longer feed, and die shortly after spawning. The sterilized males act as secret agents, swamping reproductive females with their useless genetic information. “We are creating a lottery that the females can’t win,” Johnson says. “They have a one in 100 chance of finding a normal male.”