Sea Lamprey fish is the largest of the lampreys. Adult specimens, often up to one metre in length, migrate in spring from seas into rivers, where they can be seen from March to June. Between May and July they gather in the shallow parts of the river, where the water current is strong and the bottom covered with stones. With the help of their sucking mouth the females remove stones from the water bed and prepare the spawning ground. The digestive system of adult lampreys degenerates during their journey upriver, so that they cannot eat and die soon after spawning.
The lamprey larvae have eyes covered with skin and their mouth is toothless but has distinctive fringed lips. They live in freshwaters in river bottom mud for about four years and then change into adult fish and migrate back to the sea. The mouth of the adult lamprey is funnel-shaped and covered with fine horny teeth; in addition it has a large fleshy tongue, which works in and out like a piston rod. In the sea lamprey live parasitically on various species of fish, sucking their body juices and crushing their muscles, so that they often leave deep circular wounds on the bodies of their prey.
The basic colour of the sea lamprey's body is grey-green with a striking marble-like pattern, whilst the belly is white. It lives close to the European coastline from Scandinavia as far as the eastern shores of Italy. It also inhabits the western Atlantic ranging from Nova Scotia to Florida. It is this lamprey which entered the Great Lakes (through the Welland Canal) and which became a serious pest to the native fishes.
Maximum size and weight: 100 cm, 1 kg.
Identifying characteristics: Typical teeth coverage of the whole mouth funnel; dorsal fin divided into two parts, the back part of it joined to the caudal fin.