Photo Source: US Fish and Wildlife Service

Lampreys are very strange fish. In the US they are often confused with eels. The biggest difference between the Lamprey and an eel, is that the eel has a jaw, while the Lamprey its jaw less. When the Lamprey becomes an adult its size ranges from 2 feet to 30 inches long. It is a mottled brown on top and a lighter color below. During mating season the lighter areas become bright yellow. The Lamprey lives in the sea but when it is time to reproduce it heads into fresh water. When they enter fresh water to spawn they no longer feed so no other fish are in danger. After the eggs are deposited and fertilized the adult Lampreys then die. One can't help but feel sad upon hearing this, but nature acts in mysterious ways. The eggs remain unattended and unprotected. Luckily the time to hatching is short and in about two weeks the eggs begin to hatch When hatched the larvae then drift down stream and when they reach a sandy or silty area they burrow into it. The larvae are born blind, toothless and with a hood over their mouth. They are so small that they are barely visible to the human eye when they are born. The Lamprey will remain in fresh water until they decide to head for the ocean, which could take up to ten years. One the Lamprey heads into the ocean it become almost like a vampire. It exists by sucking the body fluids out of other fish. The Lamprey will stay in the ocean for only one or two years.

As Lampreys grow into adulthood the hood disappears and teeth begin to appear on their tongue and on the sucking disk. Along with this they develop eyes. The Lampreys that are in the landlocked areas will attach themselves to other fish when the predatory phase approaches even though they are in fresh water. If the fish are large than this will not be fatal. This type of attack only lasts up to two year of their life as in the oceans. Many trout have been caught that show the scars of Lamprey attacks that they have survived.

Lampreys attached to lake trout
Photo Source: US Coast Guard

Ocean Lampreys can be found in many places. They exist along the coast of Europe and North America. Some are landlocked and exist their whole life in places like the Great Lakes. It is estimated that there are about 30,000 of these creatures in the Connecticut River. When Lampreys are in their predictor phase they can cause quite a bit of damage to other fish, even those that don't die.

Fish damaged by Lamprey attacks
Photo Source: US Fish and Wildlife Service (Photo Cropped)

Sea Lampreys became the top predictor in Lake Superior in the late 1940s. The US Government decided it had to somehow block passage from the oceans to the fresh water areas so that the Lampreys could not get to the Great Lakes and destroy the fish there. For over seven years the government worked on a chemical solution. What they were looking for was a chemical that they could put into the streams that would kill Lamprey without causing damage to the rest of the fish. The chemicals worked and are still in use today. The US and Canada now control fish in the Great Lakes under the Great Lakes Fishery Commission. Later in 1959 mechanical weirs and electrified barriers were tried but didn't work out and were removed. It seems that during high water and power failures the Lampreys would still get in. The sea lamprey controls now in use include low-head barrier dams, stream velocity barriers, safer and more effective electrical barriers, mechanical trapping, and the release of sterile male sea lampreys, which compete with normal males for mates but produce no offspring.