Invasion of the Vampire Fish
How good science saved commercial fishing in the Great Lakes
I was only 10 when I first heard my father and his brother discussing the near-total disappearance of Lake Erie’s lake trout and walleye. We were dining on platters of succulent yellow perch, also called ring perch, at a popular seafood restaurant in Port Clinton, Ohio, located in the western basin of Lake Erie.
My understanding of their conversation was limited to the specter that something horrible had invaded Lake Erie and killed off most of the lake trout, walleye and herring, all tremendously important to commercial fishing.
My elders did not use words like “invasive” and “species;” it was 1959, after all. Had they, I wouldn’t have known what they meant anyway. It was easier to imagine what sort of monster could kill most of the fish in Lake Erie, and I did not lack imagination as a child.
A key word in John Irving’s 1978 novel “The World According to Garp” is a misunderstanding by the young Garp when he hears about a dangerous undertow at the beach, hearing instead the word undertoad. Garp subsequently avoids swimming in the Atlantic waters, where he believes a giant toad lies in wait for its victims.
In my young mind, I imagined a hideous monster like the one in the classic B-movie “The Curse of the Swamp Creature.” At the time, I thought there was no way I would ever swim in Lake Erie again.
It would be another 10 years before I began working with the Ohio Department of Natural Resources. Only then did I learn that the “monster” of the Great Lakes was a sea lamprey, a hideous creature not native to the Great Lakes. But these bloodsuckers would change the course of history in and around the lakes.
Let’s hold off a bit from delving into the nature of the beast until we discuss the history of the Great Lakes. Please be assured that you will be repulsed by this monstrosity of nature soon enough.
The Great Lakes – Ontario, Erie, Huron, Michigan and Superior – make up 21% of the world’s fresh surface water and are relatively new additions to the geography of the U.S. and Canada. These freshwater lakes came about when massive ice caps of the Pleistocene Ice Age began melting and filling in the great basins created by the scouring action of the glaciers.
This significant change in topography started around 10,000 years ago and finally took the familiar form of our Great Lakes about 3,000 years ago. In a very real sense, these five bodies of freshwater are a slow-moving stream leading ultimately to Niagara Falls and the Atlantic Ocean. It is important to remember this fact when we discuss the invasion of marine vampires that destroyed commercial fishing for several decades.
Our culprit, the Sea Lamprey, is not native to the Great Lakes, although four smaller, less predatory lamprey species are indigenous to these waters.
The Great Lakes Fishery Commission describes the sea lamprey (Petromyzon marinus) as “Parasitic fish native to the Atlantic Ocean. Sea Lampreys, which parasitize other fish by sucking their blood and other body fluids, have remained largely unchanged for more than 340 million years and have survived through at least four major extinction events.”
The sea lamprey has no jaws or other bony structures, unlike other fish. Its skeleton is composed entirely of cartilage.
Sea lampreys are creatures only their mothers could love—not that they ever see their mothers after they spawn. They are often mistaken for eels, which they are not. Their mouth is unique among other fish, having a sizable sucking disk replete with rows of sharp teeth and a rasping tongue.
Adult sea lampreys attach to bodies of freshwater and commercially viable fish, such as lake trout, whitefish, walleye and ciscos (freshwater herring). Upon attachment, the armament in the mouth immediately begins to cut and rasp through the scales and skin.
The marine vampire then stays attached and proceeds to drain the victim of its blood and sometimes its organs, not dropping off until the fish dies, and the exsanguinated carcass settles to the bottom of the lake.
More often than not, a single fish may host several sea lampreys simultaneously. A single lamprey can consume over 40 pounds of fish during its feeding period.
Knowing the sea lamprey’s life cycle is key to understanding how a single species of parasitic (also predatory) fish could destroy an entire industry in the Great Lakes – commercial fishing. As we will see later in this article, that is no exaggeration.
Buffalo, Milwaukee, Chi-cago, Toronto, Cleveland and Detroit are just a few examples of cities originally founded on commercial fishing in the Great Lakes.
One aspect of the Sea Lamprey should come to mind when discussing a creature indigenous to saltwater that invades and thrives in freshwater lakes. Generally speaking, saltwater fish cannot tolerate fresh water due to cellular osmosis. Fresh water causes the fish to accumulate water in its cells, resulting in extreme bloating and death. The Sea Lamprey adjusts physiologically to lake water. They are exceedingly hard to control, as we shall see.
The sea lamprey, an invader of the Great Lakes, starts its life as an egg deposited in tributary streams. After hatching, the newly minted larvae bury themselves in the mud or silt in the stream bed. This non-parasitic stage can last three to 10 years before developing into the Transforming Phase.
The sea lamprey’s juvenile phase involves the formation of eyes and gruesome-looking oral disks. The so-called Transformers, now parasitic juveniles, head downstream into the lake and spend 12 to 18 months gorging on the blood of their host fish.
In the winter or early spring, the juveniles cease feeding and make their way up a tributary stream to spawn. As they go upstream, they mature and begin mating, only to die after spawning. Thus ends the ancient life cycle of the sea lamprey.
From pre-Columbian times to the present, Indigenous tribes of the Great Lakes were subsistence fishers. Fish, particularly lake trout, was essential to their diet and health. The abundance of fish also created trading with other tribes distant from the Great Lakes.
After the arrival of the Europeans in the 16th century, a new and aggressive form of fishing began. The white settlers to the area saw these lakes as having a limitless supply of fish and searched for new ways of taking larger catches, beginning with spears and traps and leading to more efficient nets.
The decline of fish populations in the Great Lakes began long before the sea lamprey made its way around Niagara Falls and, eventually, into all five lakes.
Old black-and-white photographs show fishing boats brimming with whitefish and lake trout up to the gunwales. The fishermen truly believed that the store of fish was inexhaustible, and they took full advantage of this faulty belief.
The thousands of low-head dams that settlers built for mills added more pressure on fish populations. Trout and whitefish lost access to essential tributary streams suitable for spawning, and their numbers dropped accordingly. As is often the case with the disappearance of native fish and other wildlife species, humans are involved.
And, indeed, the sea Lamprey would have not made its way from its native Atlantic Ocean to and through all five of the Great Lakes, had it not been for man’s handiwork.
For example, the nearly 200-foot-high Niagara Falls served to halt most marine invasive species, but not all. In 1988, the devastating zebra mussels found their way into the Great Lakes from ballast water discharged by vessels going through the Welland Canal, where they wreaked havoc on fish populations and even some species of shore birds. The zebra mussels copiously reproduce and filter vast amounts of water to obtain plankton, their food source, leaving little left to support native fish.
The Welland Canal bypasses Niagara Falls, allowing sea-going vessels to pass through Lake Ontario and, ultimately, all the Great Lakes. When engineers improved the canal in the early 1900s, all obstacles preventing sea lampreys from entering Lake Ontario were gone— and the dreaded sea lamprey arrived.
It wasn’t long before reports of encounters with sea lampreys came from commercial fishermen working the lakes and people fishing the tributary streams. At that time, nobody knew what these curious creatures were, and believed them to be eels, marine creatures native to the Great Lakes.
Commercial fishermen first reported the sea lamprey in Lake Ontario in 1835. It would be nearly a century later when a fishing boat working Lake Erie’s Canadian side hauled in a whitefish with a wriggling 24-inch sea lamprey firmly attached to its side. The fishermen had no idea what the creature was at the time.
The gravity of the situation became clear when a group of young men arriving at a popular swimming hole in Michigan’s Ocqueoc River found it swarming with thousands of wiggling sea lampreys migrating upstream to spawn. The boys reported what they saw to a game warden and, soon after, it became apparent that the sea lamprey was invading the waters of the Great Lakes.
By 1936, the sea lamprey was a devastating problem in Lake Michigan and Huron. Two years later, fishermen hauling in their nets in Lake Superior found large numbers of lake trout with lampreys dangling from their bodies.
In 1940, fishermen in Lake Huron caught 2,726,000 pounds of lake trout, but by 1946, the number had dropped precipitously to 760,000 pounds. Commercial fishing appeared to be doomed, so the governments of Canada and the U.S. created the Great Lakes Fishery Commission to study the problem and find ways to control the sea lamprey.
With the imminent collapse of the commercial fishing industry and the complete life cycle of the sea lamprey unknown, it was clear that the governments of the U.S. and Canada would have to step in to get the ball rolling.
In the late 1940s, the U.S. Congress conducted hearings on the issue, resulting in modest funding for research to find effective ways to control the sea lamprey. In 1950, a young researcher named Vern Applegate had the opportunity to earn his PhD by detailing the sea lamprey’s life cycle to find its vulnerability.
As Applegate’s research commenced, it soon became clear there were three possibilities to identify the weak link and create controls:
1. Prevent spawning.
2. Destruction of larval stage lampreys.
3. Eradication of new transformers migrating back to the lakes.
Initially, the researchers believed that preventing spawning runs offered the best chance of success, but they were wrong. Fish and wildlife employees set up gates and screens on many streams in the U.S. and Canada, but the sea lampreys’ numbers were largely unaffected.
The same was true of halting the new transformers migrating downstream, so they turned to destroying the larval stage lampreys. Success would require finding a chemical that would selectively kill the larva while it was snug in the mud in the streambed.
It would take nearly 10 years and the testing of 5,280 different chemicals before stumbling upon a lampricide that would kill the larva using a two-parts-per-million solution of a chemical called TFM (3-trifluoromethyl-4-nitrophenol).
The beauty of this chemical is that it is a true lampricide; TFM does not harm other fish, insects, birds and mammals, including humans. Likewise, the continued use of TFM has reduced the sea lamprey population in the Great Lakes by more than 90%, so it has been overwhelmingly successful in restoring commercial (and sport) fishing in our beautiful northern lakes.
Still, after researching this article, I had a few questions about the future of sea lamprey control and commercial and sport fishing. So, I made up some questions for the Great Lakes Fishery Commission that I also thought you may have:
Will the sea lamprey eventually be entirely removed from the Great Lakes?
“It’s unlikely they (the sea lamprey) will ever be completely eradicated, and ongoing control measures are crucial to maintain a healthy fishery.”
Are there any new methods of further reducing the population of sea lamprey?
“Sea lamprey pheromone control exploits their keen sense of smell by using attractant pheromones to lure them into traps or unsuitable habitats, and alarm cues to repel them from certain areas, disrupting their spawning and migration behaviors.”
Author’s Note: Pheromone control is a promising newer method that relies on only one single molecule, the sea lamprey male sex hormone, instead of complex chemical compounds.
What measures have been taken to prevent Atlantic sea lamprey from getting beyond Niagara Falls?
“Male sea lampreys are trapped, sterilized and released into the St. Marys River. The sterilized males compete as aggressively as normal males, wasting the spawning potential of female sea lampreys. The sterile-male-release-technique reduces sea lamprey spawning success over the long-term.”
What effect has success in controlling sea lamprey had on lake trout populations and commercial fishing in the Great Lakes?
“The Great Lakes Fisheries Commission announced that lake trout populations have rebounded. In 2021, commercial and recreational anglers harvested over 463,000 pounds of lake trout from Lake Superior. The Great Lakes fishery is now valued at over $7 billion annually and supports more than 75,000 jobs.”
Well, it’s time to sign off and put my “Gone Fishing” sign on the door.
Ken Springer
ken1949bongo@gmail.com
Citations are available upon request.