Lamprey Eel an Invasive Predator-parasite: Unwelcome Guest in Our Waters

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The lamprey eel is an invasive freshwater fish specie to the freshwater Great Lakes and tributaries. Measures to control its spread into streams and lakes are ongoing and it is a near-stalemate at best.

Lampreys - Ocean-going Eels in Freshwater Lakes

The marine lamprey of the Atlantic Ocean have made their way inland to fresh water lakes formerly denied them, infesting the Great Lakes and the tributary rivers that feed into them. A dramatic loss of bio-diversity is resulting as efforts to curtail their population and spread is underway.

Efforts are ongoing to slow or reduce the invasion, but no practical and permanent solution exists at this time. Scientists have studied over 3000 different chemical aids, searching for the best lampricide that does as little damage to local fish and wildlife populations as possible. The best efforts only slow the damage, such as the selective pesticides such as “TMF” ( 3-trifluoromethyl-4-nitrophenol) that targets only lampreys, and use of netting and artificial damming to prevent the spawning migration of this pest. Other control measures such as use of another granular preparation called “Bayluscide” which is more cost-effective and also targets the larval stage of the lamprey. This preparation can have potential harm to desirable local fish so this agent is used only in specific circumstances (during certain hatching or migration occurrences) where it will do the most good at eradication of the lamprey larvae and the least harm to other species.

Lamprey Eel

print showing lamprey eel and relationship to host fish from which it attaches itself and feeds

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The marine creatures known as lamprey are not true eels or are they correctly called a fish for they lack certain attributes of either. These ocean-going creatures enter fresh water to reproduce. Due to the activities of man in the previous and current centuries, they have found ways into fresh water lakes that formerly were unavailable to them. Presently, they inhabit all of the Great Lakes and the Finger Lakes as well, and many rivers and tributaries thereof.

Invasive Specie Lampreys Unbalance the Eco-System

They wreck havoc on local species in their feeding cycle, for which local fish have no developed defense against. It is believed that there are millions of them in the new territories of these fresh water lakes. They critically damage the fish they feed upon, creating large open wounds where they rasp away at the flesh and tissues for their food, drinking the blood of their victim. Only about one of every 7 fish will survive an encounter with these water vampires. In the 1950s, nearly every fish caught in Lake Huron showed signs of lamprey attacks, some with as many as ten separate wounds! The sport fishing industry was nearly devastated.

Lamprey Eels are Edible, Considered a Delicacy

Western culinary tastes do no consider the lamprey eel to be edible so there is no marketability for them. In some European countries like Portugal they are considered to be a delicacy and thus, there is a sustaining market for them. Smoked eel is also a delicacy in Poland. Lamprey are also eaten in the countries of Spain, France, South Korea, Sweden, Finland and the Baltic nations. In The U.K. they are usually used as bait for fishing (dead and cut up) and not for consumption.

Lampreys range in size from 5 to 40 inches long depending upon the specie, with the land-locked varieties being shorter than the ones that have access to large lakes and the sea. A female lamprey eel that spawns will lay as many as 60,000 eggs and a 90% survival rate for these eggs is cited.

Both the male and female die shortly after spawning. Even the male that does not spawn (as in a captive environment) will die due to a buildup of poisonous metabolic substances, accordingly to a 1985 report by the National Research Council of Canada. Upon becoming a free-swimming entity, they are compelled to mate before they die.

After about two weeks, the newly hatched eggs enter a larval stage as bottom-feeders, where they siphon the water and silt for minute diatoms, micro-organisms and whatever else they can ingest. They live as bottom-dwellers for the first 3 to perhaps as long as 17 years. It was at one time believed that these bottom dwellers were separate and distinct specie due to this very long larval state.

The metamorphosis they undergo is a remarkable one rivaled only by that of amphibians such as newts and frogs.

There is a radical rearrangement of their internal organs and they become a fully-fledged free-swimming entity. From about early to mid July and continuing to the end September, their rudimentary eyes develop into fully functional eyes. An funnel-shaped disc-like sucking mouth becomes lined with teeth and a grasping tongue with sharp barbs develops. A color change occurs. They change from dark brown to a blue-grey on the backs with silver-white on the ventral sides. They leave the rivers and tributaries and invade the larger lakes, seeking a large host to prey upon, for food. It is this stage of their life cycle that they begin to create havoc and destruction upon the fish. Attaching to a large host fish, they will eat and suck for the next year to year and one-half until they reach their full adult size, to the detriment of their host fish. They detach from their host, which now wastes away from infections in the open wound they leave behind, a wound that does not heal. The adult lamprey, fully fledged, is now ready to return to the shallower rivers to spawn and repeat the process all over again (National Canadian Research Council, 1985.)

Lampreys of the Humber River, Toronto CANADA

Last summer I got to witness up close some of this research being done on the Humber River which empties into Lake Ontario. Several researchers had live-catch traps in the river to capture adult specimens of Lampreys, take weight and length measurements mark the catch with a special notch on their fins. The lampreys were then released.

I asked that if these are invasive and bad, -why release them? They study was to determine recapture numbers which is a derivative of their range and estimated numbers. If a lamprey is recaptured oftener or not at all in a certain period of time, this provides some useful data as to their population and dispersion. I was not told of which way this information is derived, whether oftener recaptures means many or fewer, etc.

The estimated number of lampreys in Lake Huron are said to be about equal to the estimated total numbers of lampreys in the other four Great Lakes combined.

Efforts to improve the water quality may actually have a deleterious effect making the lamprey populations expand even faster and allow them to move into areas where they are not formally abundant.

Clean water is always desirable and best, but more studies are needed and new and more effective ways to manage this invasive specie. The Great Lakes are becoming cleaner and as a potential result we can expect to see an increase in the numbers of lamprey eels. Ridding them completely from our lakes and rivers is probably not possible or attainable.

-Some quotes, taken directly from an Environment Canada website:

  • “…By the 1950s, (the) sea lamprey had helped bring the once vibrant Great Lakes fishery to the brink of collapse. Virtually every fish caught had a lamprey wound; some bore the scars of 10 or more attacks.”


  • “…Today more fish are destroyed by sea lamprey than all other causes combined, including natural causes and sport, tribal and commercial harvest.”

Close-Up of the Mouth of a Lamprey Eel

lamprey eel attached to aquarium glass

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They have a ferocious-looking mouth filled with rasping teeth which they use to rasp the flesh of their host fish and consume its blood and tissues. An anti-coagulant in their saliva causes the wound to remain fresh and weeping sustenance to the parasite, preventing the wound from healing while the parasite remains attached. They not only drink the blood and fluids of their host, they use their rasping tongue to scrap flesh and tissue to consume. The host often dies from the injuries it sustains from these vampires.

Lamprey Eel Immune System and Ability to Detoxify

Nature magazine has suggested that these creatures possess a specialized immune system and have aspects of which are unrelated to the antibodies found in mammals. Also cited are that lampreys seem to have either a high tolerance for iron overload in their bodies or that they have the ability to detoxify this metal from their system. Lampreys can be found in water considered somewhat polluted and still fare well. Water with high iron content (such as near a waste treatment plant, municipal water outlets, etc) is not preferred by most other fish but lampreys seem to tolerate it well. Perhaps if this is a detoxification process they employ, it can be studied and a process or antidote might be discovered and applied to benefit other fishes. The ability for tuna, cod and other commercial fish to rid themselves of toxic mercury and other heavy metals built-up in their bodies for instance, would be a valuable result of such findings.

Close-Up of a Lamprey Mouth

close-up of a lamprey eel mouth parts

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From Wikipedia, comes mention of lampreys from literature;

Vedius Pollio, a slave owner, was punished by Augustus for attempting to feed one of his slaves to the lampreys in his fishpond for the clumsy act of having broken a crystal cup;

one of his slaves had broken a crystal cup. Vedius ordered him to be seized and to be put to death in an unusual way. He ordered him to be thrown to the huge lampreys which he had in his fish pond. Who would not think he did this for display? Yet it was out of cruelty. The boy slipped from the captor’s hands and fled to Caesar’s feet asking nothing else other than a different way to die—he did not want to be eaten. Caesar was moved by the novelty of the cruelty and ordered him to be released, all the crystal cups to be broken before his eyes, and the fish pond to be filled in…

-Lucius Annaeus Seneca (often known simply as Seneca, or Seneca the Younger)

(c. 4 BC – AD 65)

Lamprey Eel as a Food Item

lamprey eel cooked into a stew

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It only looks revolting? Cooked in its own blood, I have read. Despite it’s unappealing appearance, it is said to be actually quite good. I have my reservations about that, but bon appetit my friends! There’s more where that came from so, -eat up!

View a Live Lamprey Eel