Sea Lamprey
Sea lamprey first appeared in Lake Ontario in the 1800's. For many years they couldn't
reach the rest of the Great Lakes because of Niagara Falls. The opening of the Welland
Canal in 1829 gave them access to the rest of the lakes. By 1938 they had spread
throughout the Great Lakes. The arrival of the lamprey devastated the lake trout
population. In the early 1940's 11 million pounds of trout were caught each year in Lake
Michigan. Fifteen years later that number was only 200,000 pounds, less than 2% of the
previous catch! That pattern repeated itself in the other Great Lakes.
Since the early 1950's a concerted effort has been made to reduce the sea lamprey population. Electric barriers and lampricide, a chemical that kills the lampreys, have helped keep the population to a manageable level. This has allowed the native fish populations to rebound. However, lamprey are still a problem in the Great Lakes. It is estimated that they are responsible for 20% of all lake trout deaths each year. Also, in order to control them, lampricide has to be released into streams and rivers and the Great Lakes frequently. It is unknown how this could affect the environment of the Great Lakes in the long term.