What is the killer fish in the Great Lakes?

The Great Lakes, home to a diverse range of species, have been invaded by a deadly predator – the sea lamprey. This parasitic fish, native to the northern and western Atlantic Ocean, has become a significant problem for the Great Lakes ecosystem.

The sea lamprey, often mistaken for an eel due to its similar body shape, is among the most primitive of all vertebrate species. It lacks scales, fins, and gill covers, and like sharks, its skeleton is made of cartilage.

What makes the sea lamprey a killer fish is its disc-shaped, suction-cup mouth, ringed with sharp, horny teeth. It uses this to latch onto fish, rasping away the fish’s flesh with its rough tongue to feed on the host’s blood and body fluids. Each lamprey kills about 40 pounds of fish every year.

Sea lampreys invaded the Great Lakes in the 1830s via the Welland Canal, which connects Lakes Ontario and Erie. Within a decade, they had gained access to all five Great Lakes, where they quickly set to work predating on the lakes’ commercially important fishes, including trout, whitefish, perch, and sturgeon.

Today, the Great Lakes Fishery Commission coordinates control of sea lampreys in the lakes, which is conducted by the U.S. Fish and Wildlife Service and Fisheries and Oceans Canada. They set up barriers and traps in the streams that feed the lakes to prevent the lamprey’s upstream movements, and apply special chemicals, called lampricides, that target lamprey larvae but are harmless to other aquatic creatures.

In conclusion, the sea lamprey, an invasive species, is the killer fish in the Great Lakes. Its parasitic nature and destructive feeding habits pose a significant threat to the native fish populations of the Great Lakes. However, efforts are being made to control and reduce their numbers to protect the biodiversity of these vital freshwater ecosystems.