The only regular predators of the sea lamprey are humans, who hunt them both for food and for the preservation of other fish species, to which lampreys are a threat. Lampreys die soon after spawning, so they have a maximum lifespan of around five years.
Sea lampreys are native to the Atlantic ocean, where their range extends along the coasts of the United States and Europe. They have also been introduced several times to the freshwater Great Lakes in the United States, and a population still exists there. Lampreys are hunted, particularly in the Great Lakes, in part because they are an invasive species that can devastate native fish populations. Indeed, the species is partially responsible for the collapse of the Great Lakes fishing industry in the 1800s. They are external parasites of other fish, consuming their blood and skin. Eventually, sea lampreys can break down a fish's body while it is still alive. Lampreys do not have a preferred prey species, and attack any fish in its area. The killing of sea lampreys is accomplished both through traps and pesticides, which are targeted specifically to lampreys.
Lampreys cease feeding as they prepare to spawn, and their digestive systems break down. Males build nests and use chemical signals to attract mates, but they provide no further parental care.