For decades, KBIC has been an active partner in assessment and control of invasive sea lamprey, which are one of Lake Superior’s most notorious fishery management challenges. These parasitic eel-like animals slipped into the Great Lakes through man‑made canals in the early 1900s, and have remained ever since, posing one the greatest ongoing threats to valuable fish stocks throughout our region.
Adult sea lamprey latch onto many commercially valuable species of fish with a suction‑cup mouth ringed in teeth, then rasp a hole in the skin, and feed on blood and body fluids. The wounds left behind on fish result in either permanent scarring, or death due to healing complications (secondary fungal or bacterial infections,
etc.). In Lake Superior, it has been estimated that a single adult sea lamprey can be ultimately responsible for the death/removal of >40 pounds of fish, and that the adult Lake Superior sea lamprey population is responsible for the loss of more poundage of fish than sport and commercial fishing means combined (GLIFWC, 2020)
KBIC-NRD AIS and Fisheries Programs work closely with partner agencies (USFWS, USGS, GLFWC, MDNR, OMF, and others) to coordinate and conduct assessment and control efforts. Understanding of the sea lamprey life cycle has led to multi-agency efforts to track and combat these invaders on a year-round basis. In particular, the timing of this “blog” is associated with recent efforts to trap downstream migrating and newly
“transformed” larval sea lamprey; those that have emerged from the sedentary stage and are headed out to Lake Superior to begin attacking fish!
Agencies deploy capture/drift nets on rivers considered to likely host large populations of larval sea lamprey (based on results of electro-fishing surveys conducted during summer months). In many instances, attempts are made to eradicate larval sea lamprey infestations in upper reaches of rivers, using select lampricides, and/or physical removal via electro-fishing, before they get the chance to “transform”. Downstream larval and transformer drift net surveys are conducted to assess relative success of upstream eradication efforts, and to estimate numbers of surviving transformers headed out to Lake Superior.
Unfortunately, sea lamprey transformers are triggered to begin the downstream migration as river temperatures plummet in the fall and winter. In many instances, transformers are captured as rivers are freezing up, making this work quite challenging! KBIC-NRD sea lamprey drift net surveys continued into December 2025, and captured dozens of transformers on their way to prey on unsuspecting Lake Superior fish!
Ultimately, data and captured sea lamprey are shared with all of our partner agencies. Retained lamprey samples are used for genetics research, or are kept alive for laboratory research and/or education/outreach at the USFWS Marquette Sea Lamprey Control Center. Capture data from these efforts are pooled with Lake Superior Basin-Wide data, and assist managers in planning on future evaluation and control throughout the region. KBIC-NRD anticipates conducting work next spring to attempt to capture adult sea lamprey ascending rivers to spawn and replenish themselves. This battle will continue!