Rachel Francis, age 10, of Annapolis, Md., for her question:
IS THE LAMPREY VERY DESTRUCTIVE?
The lamprey is a fish with a long eellike body. It is a destructive animal since it uses a circular, suctorial mouth with horny teeth for boring into the flesh of other fishes to feed on their blood.
Scientists consider the lamprey one of the least developed vertebrates, or animals with backbones. Unlike most other fishes, the lamprey has no bony skeleton. It has a backbone called a notochord that is made of rubbery tissue called cartilage. It also has underdeveloped eyes.
The laprey 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 develop horny teeth. The lampreys skin is smooth, shiny and scaleless.
Lampreys can be found in small streams throughout temperate parts of North America, Asia and Europe. Here they grow to be about eight inches long. They are also found in rivers and lakes. Sea lampreys, growing to be three feet long, can be found in the North Atlantic and North Pacific oceans.
Large sea lampreys rank as the most destructive to 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 Wetland 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 1950s, the lampreys had killed most of the lake trout in the Great Lakes. Scientists tried to control them by putting electric weirs or fences across streams to prevent the lampreys from spawning. But the weirs were costly and difficult to maintain.
The problem was solved with a chemical called TFM that would kill lampreys but not harm other fish in the rivers. There was a sharp decline in the number of lampreys by the mid 19609.
Once the chemical TFM controlled the lamprey problem, conservationists were able to stock the lakes with coho salmon, lake trout and other fishes.
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 non parasitic lampreys do not eat. Their digestive organs degenerate and they live only until the spawning season. Then they spawn and die.
Lampreys spawn in clear water streams. The male and female dig a shallow nest in the gravel or pebbles of the stream bottom. The female deposits eggs in the nest.
Larval or young lampreys are called ammocoetes. They are blind and toothless and look like worms. The ammocoetes live in the sand and mud of the stream bottom for several years. Then they change into adults with eyes and teeth.