Sea Lamprey Slip: Great Lakes See Steady Decline

For once, the news out of the Great Lakes is not another invasive species horror story. Sea lamprey — the parasitic, jawless fish that helped gut the region's lake trout populations a century ago — are in decline across nearly all of the lakes, according to the latest assessments from the binational control program. It is a quiet, incremental victory, and for Michigan, which holds more Great Lakes shoreline than any other state, it matters deeply.

The lamprey's slide is not an accident. It is the product of decades of coordinated effort: low-dose lampricides applied to spawning streams, physical barriers that block upstream migration, and trapping programs that remove adults before they can reproduce. The program is a rare example of two nations — the United States and Canada — running a single, sustained campaign against a shared ecological threat, and it has largely worked.

A Long War, Slowly Won

For Michigan anglers and the communities that depend on them, the stakes are personal. Sea lamprey attach to fish like lake trout and salmon, rasping through scales and feeding on blood and body fluids. A single lamprey can kill or cripple dozens of fish over its life span. With lamprey pressure easing, the fishery — and the tourism dollars it supports — stands to gain, though the gains are gradual rather than dramatic.

The decline is not a reason to celebrate prematurely. Lamprey populations can rebound quickly if control efforts lapse, and climate change is already altering stream temperatures and flows in ways that could favor the species. The lesson from the Great Lakes is that invasive species management is not a one-time fix but a permanent commitment. For now, though, Michigan can take a measured win — and keep the barriers up.