The long, eel-like fish drinking the blood of this lake trout is one of nearly fifty species of lampreys, a group of jawless fishes found in temperate rivers and coastal seas.
Some species live in fresh water for their entire lives.
That is, they are hatched and grow in fresh water, migrate to the ocean to mature, and then return to fresh water to spawn. The ammocoetes stage may last up to seven years before its metamorphosis into an adult. Adult lampreys live for a year or two before spawning, and then die soon afterwards. The adults bear seven separate gill openings and have an internal skeleton of cartilage. Unlike hagfishes , with which they were once classified, lampreys have a complete braincase and rudimentary true vertebrae.