Silver Lamprey (Icthyomyzon unicuspis) are native to both the Red River basin and the Rainy River basin, including Lake of the Woods.
The native lamprey species of the genus Ichthyomyzon should not be confused with the exotic and destructive Sea Lamprey Petromyzon marinus, which wreaked havoc on native game fish in the Great Lakes before vigorous control measures brought it to check. The native lamprey have evolved with, and live in balance with, their host populations.
Adult Silver Lamprey that was sampled from the Rainy River in May
The Silver Lamprey is eel-like in shape, with a long dorsal fin that is not divided. The mouth is jawless with a large disk that when expanded is wider than the head. The disk, or mouth, of adult Silver Lamprey is full of sharp teeth.
Head of an adult Silver Lamprey showing the gill openings
Silver Lampreys begin their spawning runs into moderate to small streams with moderate current levels in June. They excavate a nest in the stream bed by moving sand and gravel substrate with their mouth to form a shallow depression. The adults die when spawning is completed. The eggs hatch and the young, called ammocoetes, burrow into sand, dark muck, or organic debris. They are not parasitic during this life stage. They remain there and feed on microscopic food for an unknown length of time.
When they change into the adult, parasitic form, they move downstream where they can find host fish to attach to. They usually remain in their adult habitat for one year before returning to a stream to spawn. Once attached to their host, they bore a hole in the skin and feed on the juices and flesh of their victim. Common hosts in the Rainy River, Lake of the Woods, and the Red River are: Lake Sturgeon, Northern Pike, and White Suckers.
When the non-parasitic ammocoetes first emerge as parasitic adults on the Rainy River, they are about the size of a big night crawler. After growing for a season, the average Silver Lamprey adult is between 9 and 14 inches in length. Color can vary between individuals, but most of the Silver Lamprey in the Rainy River are dusky gray to light brown in color.
Mouth parts of an adult Silver Lamprey
For more information on the fish of the Rainy River, Red River, or Lake of the Woods, please contact:
Assistant Fisheries Supervisor
204 Main Street East
Baudette, MN 56623
tel.: (218) 634-2522
e-mail: Assistant Area Fisheries Supervisor