Sea Lamprey (Petromyzon marinus) … invasive species like the sea lamprey can cause significant environment and economic damage.

Sea lampreys are primitive fish native to the Atlantic Ocean … they entered the Great Lakes through man-made shipping canals.  In the Great Lakes they have no commercial value and fish do not normally feed on them.

Locking jaws, their round mouths form a sucking disk filled with sharp, horn-shaped teeth that surround a rasping tongue.  Unlike most fish, a lamprey’s body has cartilage but no bones, non-scale skin, no paired fins, no lateral line, and no swim bladder.

Sea lampreys are parasitic pests … the adult sea lampreys range from 12 to 20 inches long and weigh from 8 to 13 ounces.  They attach to fish with their suction mouth and teeth, and use their tongue to rasp through a fish’s scales and skin so they can feed on its blood and body fluids.  A single sea lamprey will destroy up to 40 pounds of fish during its adult lifetime.  Sea lampreys are so destructive that, under some conditions, only one out of seven fish attacked will survive.  Sea lampreys prey on all type of fish, such as lake trout, salmon, rainbow trout (steelhead), brown trout, whitefish yellow perch, walleye, catfish, and even sturgeon.

Life Cycle
Adult sea lampreys swim upstream to spawn and then die.  Fertilized eggs hatch into small, worm like larvae which burrow into stream bottoms.  The larvae feed on debris and small plant life (algae) for an average of 3 to 6 years before they transform into the parasitic adult.  The adults migrate into the Great Lakes where they spend 12 to 20 months feeding on fish.  The complete life cycle, from egg to adult, can take an average of 5 to 8 years to complete.

Control Efforts

Lampricide
The primary method to control sea lampreys utilizes a lampricide, called TFM, which kills sea lamprey larvae in streams with little or no impact on other fish, aquatic plants, invertebrates, and wildlife.  About 175 Great Lakes streams are treated at regular intervals with lampricide to kill larval sea lampreys.  Despite the success of TFM, it is a costly control method … other alternative methods are being implement to help control the cost.

Barriers
Barriers have been constructed to block the upstream migration of spawning sea lampreys; most barriers allow other fish to pass with minimal disruption.  Barriers have reduced or eliminated altogether lampricide treatment on many streams.

Newer barrier designs include electrical barriers that repel sea lampreys during the spawning run without risk to other fish or animals and adjustable-crest barriers which can be inflated during the spawning run and then deflated to allow other fish to pass during the rest of the year.

Sterile-Male-Release-Technique
The sterile-male-release-technique aims to reduce the success of sea lamprey spawning.  Each year male sea lampreys are collected and sterilized.  When they are released back into streams the sterile males compete with fertile males for spawning females.  Spawning sea lampreys and sterile males die after the spawning run.

Assessment has indicated that fewer sea lamprey eggs hatch in streams where the sterile-male-release-technique is used.

Trapping
Sea lamprey traps are operated at various locations throughout the Great Lakes, often in association with barriers.  Traps are designed to catch lampreys as they travel upstream to spawn.  Male lampreys caught in the traps are used for the sterile-male-release-technique.