The Lake Michigan Giant Lamprey, also known as the Sea Lamprey (Petromyzon marinus), is a parasitic fish native to the Atlantic Ocean that has invaded the Great Lakes, including Lake Michigan. This invasive species poses a significant threat to the native fish populations and the overall health of the Great Lakes ecosystem.
The Impact on the Fishery in Lake Michigan
The sea lamprey’s arrival in the Great Lakes has had a devastating impact on the region’s fishery. As a parasitic predator, the sea lamprey preys on most species of large Great Lakes fish, including lake trout, brown trout, lake sturgeon, lake whitefish, ciscoes, burbot, walleye, catfish, and Pacific salmonids like Chinook and coho salmon and rainbow trout/steelhead.
Before the sea lamprey invasion, Canada and the United States harvested about 15 million pounds of lake trout in the upper Great Lakes each year. However, by the late 1940s, the catch had dropped dramatically, to approximately 300,000 pounds, about 2% of the previous average. This decline in fish populations has had significant economic implications, affecting the livelihoods of people involved in the fishing industry.
How Sea Lampreys Affect Native Fish
The sea lamprey’s parasitic feeding behavior is the primary reason for the devastation of the Great Lakes fishery. The sea lamprey attaches to fish with its suction cup mouth, then digs its teeth into the flesh for grip. It then rasps through the fish’s scales and skin with its sharp tongue and feeds on the fish’s body fluids by secreting an enzyme that prevents blood from clotting.
Host fish in the Great Lakes are often unable to survive sea lamprey parasitism, either dying directly from an attack or from infections in the wound after an attack. Surviving fish often suffer from weight loss and a decline in health and condition.
Control Methods
The Great Lakes Fishery Commission has implemented various methods to control the sea lamprey population and mitigate its impact on the fishery. The primary method involves using pesticides selective to lampreys, known as lampricides, to kill larval sea lampreys in Great Lakes tributaries.
In addition to lampricides, a combination of barriers and traps are used to prevent the upstream migration and reproduction of adult sea lampreys. The Great Lakes Fishery Commission spends around $20 million annually to keep the sea lamprey population under control.
Additional Facts
- Sea lampreys can grow up to two feet long and live for about six years as predators and almost ten years as filter feeders.
- A single female sea lamprey can produce as many as 100,000 eggs.