SEA LAMPREY, SCOURGE OF THE GREAT LAKES
SEA LAMPREY 101
Sea lampreys (Petromyzon marinus) are an eel like fish prevalent in the Atlantic ocean, but have since become an invasive nuisance in the Great Lakes. The lamprey order, Petromyzontiformes, is an ancient one having lasted for 340 million years, surviving four major mass extinction events (GLFC, 2016). Sea lampreys are a fish parasite and have a long tubular body composed of cartilage a large sucker like mouth filled with teeth. They are the largest and most predacious of all their family, using their sucker to cling to a fish and teeth to penetrate the fish’s tissue. Once ruptured, the raspy tongue pulls scales away as their saliva secretes an anticoagulant to prevent the blood from clotting. After feeding, the fish is left with a hole in its tissue prone to infection (IDNR, 2017).
Left: Sea Lamprey mouth (NCRAIS, 2017).
Right: Lampreys attached to a trout (GLI, 2017).
WHAT IS THEIR LIFE CYCLE?
Larval lampreys hatch from eggs buried in the substrate of inland streams. Once they hatch, the current carries them further down stream until they burrow into the silt. Once planted they remain in this stage for about 4-6 years as bottom feeders, eating algae and other organic material. After this stage, the adult parasites leave and move out to sea or other open water to feed on fish. After a period of 12-20 months, they return into the tributaries to spawn and die (GLFC, 2016).
Right: Sea Lamprey life cycle (GLI, 2017).
HOW DID THEY ENTER?
Most researchers speculate the lamprey gained entrance to the Great Lakes area by means of man made locks in shipping canals. Niagara Falls blocked the lampreys entrance, but with the construction of the Welland Canal and its refurbishment in 1919, lampreys had a path around the natural barrier Niagara Falls presented, gaining a new source of open water to expand. New populations were first noted in Lake Erie in 1921, spreading into all the rest in just 25 years (IDNR, 2017).
WHY ARE THEY SIGNIFICANT?
In the Atlantic, the lamprey’s targets have co-evolved so that their parasitism does not kill the host. This is not the case in the Great Lakes, where lamprey attack any fish and kill 6 out of every 7 hosts (GLFC, 2016). If a host fish does not die of blood loss, the open wound usually becomes infected causing mortality. The high mortality rates of lamprey hosts in the Great Lakes has lead to serious financial harm in the fisheries economy. Lampreys will feed on almost any fish in the lakes and the high mortality has caused significant population collapses. For instance, lake trout, whitefish and chub populations declined to extirpation in the 1940’s and 1950’s from lamprey predation. Given that a single lamprey is capable of killing over 40 pounds of fish within its lifespan, their pressure continues to affect the lakes today (GLFC, 2017).
HOW DOES THAT AFFECT ME?
Over the decades lamprey populations have grown in size and impact. For instance, the US and Canada used to collect around 15 million pounds of lake trout a year, but this number was reduced to 300,000 pounds a year in the 1960’s. This lack of product forced many out of a job in an industry that was shrinking (GLI, 2017). Currently, the government has managed the populations and advance of sea lampreys costing $14 million annually for conservation. If these efforts were to cease, the losses would be over $500 million a year in the fisheries economy (NCRAIS, 2017). There are close to 6,000 tributaries in the Great Lakes, and at least 433 of them have sea lampreys, and 250 are treated. The methods used include dispersing lampricide, installing low head dams and setting traps. All of which cost money a portion of which is subsidized by taxes (GLI, 2017).
Left: Lowhead dam (GLI, 2017).
Right: Lampricide application (GLI, 2017).
SO WHAT?
Invasive Sea Lampreys are causing a lot of problems in the lake biota, that has environmental and economical impacts. The cost to mitigate their damage, and conserve the natural species in part comes out of the tax payer’s pocket, showing that lampreys are a nuisance affecting everyone, even those who do not interact with the Great Lakes.
REFERENCES
Great Lakes Fishery Commission (GLFC). Great Lakes Fishery Commission – Sea Lamprey. 2017 [accessed 2017 Sep 28]. http://www.glfc.org/sea-lamprey.php
Great Lakes Fishery Commission (GLFC). Sea Lamprey a Great Lakes Invader. 2016 [accessed 2017 Sep 28]. http://www.glfc.org/pubs/FACT_3.pdf
Great Lakes Inform (GLI). Sea lamprey (Petromyzon marinus). Great Lakes Inform. 2017 [accessed 2017 Oct 1]. https://greatlakesinform.org/knowledge-network/1077
Indiana Department of Natural Resources (IDNR). Sea Lamprey. Aquatic Invasive Species. [accessed 2017 Oct 1]. http://www.in.gov/dnr/files/SEA_LAMPREY1.pdf
Michigan Department of Natural Resources (MDNR). Michigan Invasive Species. [accessed 2017 Oct 1]. http://www.michigan.gov/invasives/0,5664,7-324-68002_73845-374989–,00.htmloutput–1edq1f5
NOAA Great Lakes Environmental Research Laboratory. NOAA National Center for Research on Aquatic Invasive Species (NCRAIS). Nonindigenous Aquatic Species. [accessed 2017 Oct 1]. https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspxSpeciesID=836&Potential=N&Type=0