Lamprey, << LAM pree, >> is any of a group of fish with long, eellike bodies. Scientists consider lampreys among the least developed vertebrates (animals with backbones). Unlike most other fishes, a lamprey has no bony skeleton. It possesses a backbonelike notochord made of rubbery tissue called cartilage. A lamprey has fins on its back but not on its sides. Its round mouth has no jaws but can create strong suction. Adults of some species (kinds) of lampreys attach themselves to other fishes by sucking with their mouths and clamping with their teeth. They then feed on the animals’ blood and other body fluids.
Body.
A lamprey’s skin is smooth, shiny, and scaleless. Brook lampreys live in small streams throughout temperate (mild) parts of Europe, Asia, and North America. These animals grow about 8 inches (20 centimeters) in length. Larger species of lampreys inhabit rivers and lakes. Sea lampreys, which may grow as long as 3 feet (91 centimeters), live in the North Atlantic and North Pacific oceans.
All lampreys are dull colored, ranging from light tan to brownish- or bluish-black. They do not have true bony teeth. Their teeth are horny developments that grow from the inner surface of the mouth.
Habits.
Lampreys spawn in clear, freshwater streams. The male and female dig a shallow nest in the gravel or pebbles of the stream bottom. The female deposits the eggs in the nest. Adults die after spawning. Larval (young) lampreys are called ammocoetes. They are blind and toothless and look like worms. Ammocoetes live in the sand and mud of the stream bottom for several years. They then change into adults, developing eyes and teeth.
Parasitic lampreys feed by attaching themselves to fishes, scraping a hole through the skin, and sucking out blood and other body fluids. The adults of the nonparasitic lampreys do not eat. Their digestive organs degenerate, and they live only until the spawning season. Then they spawn and die.
Destructiveness.
Large sea lampreys rank among the most destructive of fishes. As adults, they descend to the sea and prey on large fishes.
Some sea lampreys that spawned in streams flowing into Lake Ontario once entered the upper Great Lakes through the Welland Canal. Later generations of these lampreys no longer descend to the sea, but prey on lake trout, whitefish, and other large lake fishes. By the late 1950’s, they had killed most of the lake trout in the Great Lakes. Scientists tried to control the lampreys by putting electric weirs (fences) across streams to prevent the lampreys from spawning. But the weirs were costly and difficult to maintain. Researchers discovered that a chemical called TFM would kill lampreys but would not harm other fish in the rivers. The treatment of streams with this chemical caused a sharp decline in the number of lampreys by the mid-1960’s. Wildlife officials then stocked the lakes with coho salmon, lake trout, and other fishes.
