Sea lampreys belong to an ancient order of eel-like fish, most of which, including the sea lamprey, are parasites on other fish. Sea lampreys’ gory lives begin as larvae hatched from fertilized eggs. Three to six years later, these larvae swim downstream toward the Great Lakes, smooching their mouths on unfortunate fish and sinking their rows of teeth into their flesh (skip the $13 admission price to a horror movie and pull up a photo of a sea lamprey’s jawless, circular mouth instead – you won’t be disappointed). Once attached, the parasites will then suck out the unfortunate fish’s bodily fluids.
If the fish is large, it will survive the encounter, with a bullseye scar to boot. If it is small, it will die, and the sea lamprey will snuggle up to another victim with its toothy kiss. After about a year of feeding, sea lampreys detach themselves to swim upstream, breed, and die.
There are five native lamprey species in the Great Lakes, but sea lampreys are not among them. Instead, these interlopers are believed to have arrived from the Atlantic via the new canals connecting North America’s water bodies in the early 1900s. The first invading sea lamprey was fished from Lake Erie in 1921. Over the next decade, the invader was spotted in each of the other four Great Lakes, ending its conquest with Lake Superior in 1938.
The sea lamprey's arrival was not welcome. Profiting from the invader’s advantage in an ecosystem unprepared to deal with it, the sea lamprey fed with abandon, bleeding out rainbow trout, lake trout, salmon, whitefish, and catfish, among others. As it fed, local fisheries – an industry now valued at about $7 billion – began to buckle.