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Invasive Sea Lampreys: Parasitic Predators Devastating the Great Lakes Ecosystem

Author: Brave WildernessTime: 2024-01-22 22:05:01

Table of Contents

Introduction to Sea Lampreys and the Great Lakes Invasion

The sea lamprey is an invasive species that has had a hugely detrimental impact on the Great Lakes ecosystem over the past century. Looking almost alien-like with its circular mouth filled with rows of sharp teeth, this parasitic predator has a simple yet strategic life cycle that allowed it to quickly proliferate through the freshwater system.

Native to the Atlantic Ocean, the sea lamprey invaded the Great Lakes in the early 20th century through man-made canals. With no natural predators and an abundance of prey, sea lamprey populations exploded, attaching to fish and sucking their bodily fluids. Their numbers grew unconstrained, devastating populations of valuable food and game fish species.

Life Cycle and Biology

Sea lampreys have a well-structured life cycle that starts with the spawning phase. Adults leave the lakes and swim into tributary streams, where they build nests, lay eggs, and then die. After the eggs hatch, the blind larvae drift downstream and burrow into soft sediment on the river bottom. They live hidden in burrows for up to 7 years, filter feeding on detritus and plankton. When ready to feed, they go through an incredible metamorphosis, transforming into parasites with a circular, sucker-like mouth, razor sharp teeth, and a spiked tongue. The newly transformed adults then migrate out to the lakes and attach to fish using their sucker mouth. They rasp through the fish's scales and skin with their tongue until drawing blood. They release an anticoagulant that allows them to fluidly drink the blood and bodily fluids of the fish. Each adult can kill up to 40 pounds of fish during the 12-18 month feeding phase before returning to freshwater streams to spawn and die.

Mechanism of Systematic Invasion

Several key attributes of the sea lamprey's biology allowed it to invade so successfully. First, the females lay nearly 100,000 eggs each, meaning even limited numbers can explode into extremely high populations. Second, the larval stage lasts up to 7 years, so they persist undetected in riverbeds for a long time before emerging to feed. And third, they go through a radical physical transformation that equips them with specialized tools for parasitic feeding. With no natural checks and balances in place, their systematic and adaptive life cycle allowed sea lamprey populations to rapidly increase to staggeringly high levels. At their peak, it's estimated there were up to 5 million adult lampreys devastating the fisheries, with no way for native species to evolve defenses fast enough against the invading parasite.

Sea Lamprey Feeding Experiments on Animals and Humans

Given how viscerally destructive sea lampreys were to Great Lakes fish species, questions emerged if they could also attach to other animals or even humans. Controlled feeding studies have demonstrated sea lampreys will successfully feed on a variety of warm-blooded vertebrates by sucking their blood.

In his own daring experiment captured on video, wildlife educator Coyote Peterson allowed captive sea lampreys to attach to his own body, first on his forearm, then his stomach, and finally his neck. He reported powerful suction sensations and noticeable rasping from the tongue and teeth, drawing some blood on areas with soft tissue. However, likely not recognizing human blood, the lampreys detached after a short period without attempting to extract substantial fluids.

Coyote Peterson Lamprey Suction Test

In the video documentation of this human feeding trial, Peterson remarked on the incredibly strong suction sensation, akin to four times the power of a home vacuum cleaner. On softer areas like his belly and especially his neck, the razor sharp teeth dug in painfully as the sandpaper-like tongue worked to break the skin. Although the blood flow and fluids elicited an initial investigatory response, the lampreys soon disengaged without attempting to extract further sustenance from the human host.

Ongoing Efforts to Control Sea Lamprey Populations

After the alarm was raised about catastrophic losses of whitefish, trout, and other commercial and game fish species in the 1940s, concerted efforts began to research control methods to contain the parasitic sea lamprey. Starting in the 1950s, the bi-national Great Lakes Fishery Commission pioneered a highly successful program that has reduced sea lamprey populations by 90%.

Targets Within the Lamprey Life Cycle

Researchers identified key targets within the sea lamprey life cycle that presented control opportunities. The extended larval burrowing phase was pinpointed as the best area to apply selective control treatments. Teams developed specialized lampricides that could eliminate ammocoetes in their riverbed burrows without harming other wildlife. Other innovative strategies aimed at blocking adults during migration, trapping them en route to spawning grounds, using pheromones as bait to distract them and disrupt reproduction, and even leveraging alarm cues to scare adults from prime feeding areas. Each prong of attack focused on vulnerabilities in the lamprey's life cycle.

Solutions Led by the Great Lakes Fishery Commission

Starting in the 1950s, the binational Great Lakes Fishery Commission led the charge to develop sea lamprey control techniques and contain populations. Their first key breakthrough was using the pesticide TFM to target larvae burrowed in stream bottoms. Later additions such as niclosamide and bayluscides provided even safer and more effective lampricides to eliminate ammocoetes. Over time, the Commission implemented an integrated pest management strategy utilizing lampricides, migration barriers, traps, and pheromones to battle lampreys on multiple fronts. They also supported extensive research to improve tactics. This coordinated, adaptable strategy succeeded in cutting invasive numbers down by 90% and saving the vital fisheries.

Conclusion and Ways to Support Sea Lamprey Management

The story of the devastating Great Lakes sea lamprey invasion and subsequent containment efforts represents one of the greatest success stories around combatting an invasive species. Populations were cut by 90% within decades, saving innumerable tons of food and game fish from destruction by the blood-sucking parasites.

Continued vigilance and support are still needed to hold the line against these aggressive invaders. Work with the Great Lakes Fishery Commission to report any sightings of adult lampreys in unusual locations, volunteer to assist with summer assessment surveys, and donate to support the essential on-the-ground management efforts.


Q: What makes sea lampreys such a threat in the Great Lakes?
A: Sea lampreys are parasitic predators with a mouth full of sharp teeth that attach to fish and feed on their bodily fluids. They spawn in huge numbers, so without control efforts, they can decimate fish populations.

Q: Do sea lampreys bite humans?
A: Yes, sea lampreys can bite and suction onto human skin out of curiosity and hunger when blood is detected. But they do not seem interested in feeding long-term on humans.

Q: How have sea lamprey populations been reduced by 90% in the Great Lakes?
A: Through an integrated program of barriers, lampricides, trapping, and experimenting with pheromones/alarm cues that disrupt the lamprey life cycle and spawning.