Lake Superior trout numbers are now recovering. Control programs for the Great Lakes cost several million dollars each year, but they protect multibillion-dollar sport and commercial fisheries. Smaller size, different fin shape, and unique form and pattern of teeth distinguish native lamprey species from the sea lamprey. It is most common in the Mississippi, Minnesota, St. Croix, Red, and Rainy rivers and Lake of the Woods. When I collected silver lampreys in the Mississippi, they were usually attached to common carp, but they also parasitized a wide range of large fish, including catfish, walleyes, northern pike, suckers, sturgeons, and paddlefish.
Adults can parasitize large catfish and sturgeon, but most go for smaller suckers and trout.
In general, neither silver nor chestnut lampreys have had the same severe impacts on prey fish populations that the sea lamprey has produced, although silver lampreys have caused some problems in Lake of the Woods. Biologists have speculated that long-term coexistence of native lampreys and their prey has allowed them to adapt to one another. The northern brook is our smallest species, usually less than 5 inches long. It has been collected from streams in St. Louis, Carlton, and Koochiching counties. No native lampreys are listed as threatened or endangered species in Minnesota.