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

****:THE LAMPREY

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.