Forest Preserve District of Cook County, Illinois
Nature Bulletins
Newton Home Page

Introduction and Instructions

Search Engine

Table of Contents



The Lamprey
Nature Bulletin No. 106   March 8, 1947
Forest Preserve District of Cook County
William N. Erickson, President
Roberts Mann, Supt. of Conservation

The sea lamprey is another marine animal which, like the smelt, has invaded the Great Lakes and threatens irreparable damage to native fish. The Atlantic sea lampreys do not breed until about 8 years old. Then they stop feeding and, in spring travel up streams, lay eggs, linger a few weeks, then die. Centuries ago, certain of these penetrated the Lake Ontario and some of the Finger Lakes in New York, notably Cayuga Lake. Their progeny did not return to the sea but became adapted to total existence in fresh water. Niagara Falls stopped them until about 1921, when they appeared in Lake Erie, presumably by way of the Welland Canal. By 1936 they were established in Lake Michigan.

These large blood-sucking parasites have now become a serious menace to lake trout, whitefish and other commercial fishes in the Great Lakes. The federal and state governments are being urged to spend millions of dollars in constructing traps to prevent the lampreys from reaching their spawning grounds in any of the tributary streams. There are several native lampreys, some of them parasitic, but these are only from 4 to 13 inches long and do little damage to fish. The sea lampreys range from 15 inches to 2 feet in length and are killers.

This strange fish-like slimy creature has no scales, no paired fins, and is not a fish -- as is the true eel. It is one of the most primitive of the backboned animals. It has only one nostril, two beady eyes, and 7 pulsating portholes down each side that pump water over its internal gills. It has a round funnel-shaped sucking mouth equipped with row after row of sharp horny teeth. Clamping onto a big lake trout, a sea lamprey rasps a hole through the skin, injects a chemical which keeps the blood from clotting, and gorges itself until full or until the fish dies.

Although esteemed as food since ancient times, Alexander the Great, and Henry I of England, are said to have died from eating too much of the rich meat of the lamprey. Since they will attach themselves to any moving object in the water, sea lampreys are accused of breaking up swimming races in Lake Ontario at Toronto, and handicapping the racing shell of a Cornell crew in Cayuga Lake.

To return to the Nature Bulletins Click Here!
Hosted by NEWTON

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Sponsered by Argonne National Labs