In the never-ending battle to prevent blood-sucking sea lamprey from wiping out some of the most popular fish species in the Great Lakes, experts are developing a new method of control that uses the invader’s dead body.
The sea lamprey releases some sort of chemical “repellent” when there is mechanical damage done to the skin due to events such as predation. This repellent acts as a warning to other fish in the area to stay away from the potential danger in that direction. Area avoidance as a result of injury-released chemical alarm cues has not been sufficiently studied. Therefore, Xiangyu Wang and his team of scientists are investigating the effects of dead lamprey on migrating lamprey. “It may be possible to counter the lampreys during their mating season by neutralizing the hormones that attract them to their mating grounds by releasing some sort of lamprey repellent at the mouth of particular streams and tributaries,” says Wang.
Wang had done previous work on lamprey larval release of hormones. His interest in sea lampreys came from the fact that they are an ancient species of fish that has been unchanged for millions of years. “This is what makes them so successful,” says Wang. Therefore, he and his team of scientists decided to investigate the species further.
His study will use a Y-shaped water maze with dead lamprey extract continuously injected into one end. The lamprey will have a choice to either swim up the passage in which dead lamprey extract is present or to swim up the passage in which nothing was added. According to Wang, “There is a good chance that the lampreys will respond to the dead fish extract.” If this proves to be true, the team’s next step would be to specifically isolate the chemical that is causing this response and determine an effective method at spreading it. If distributed around spawning grounds, reproduction could be severely reduced and the problems associated with these leech-like creatures would hopefully be alleviated. If lampreys can not find suitable habitats to breed, then their populations will be brought under control.
Complete eradication may not be possible, but the goal is to keep the lamprey numbers low enough to prevent significant harm to the 7 billion dollar Great Lakes fishing industry. Although native to the Atlantic, they can live in fresh water and migrated to the Great Lakes through shipping canals. By the late 1940s, the prolific invaders had decimated trout, whitefish and other sport and commercial species across the lakes. They have dramatically decreased the populations of many other species of local game fish and hurt the livelihoods of many fishermen.
“They are parasites that feed on the blood and flesh of fish. With their destructive ways they have had a large impact on fish population,” states Wang. This is why research on the sea lamprey has continued to grow; a need for an effective method of control is imminent.
“The results of this study will pave the way for a method to be developed that is effective and has a low impact on the environment,” says Wang. In addition, he expects that his method will improve previous protocols. By using a maze with flowing water instead of a tank, Wang and his team will be able to more accurately model the reaction a lamprey would have in the wild.