||Freshwater. Generally associated with warmwater habitats and tolerant of variation in terms of discharge (summer flows 0.06-34 m3/s), water temperature, and substrate. Occurs principally in the mainstems of large streams. It can also occur in small to large lakes. In Lake Huron, has been collected at depths between 26 and 31 m. Spawning adults are found in streams or lakes (Ref. 89241). Ammocoetes occur in sandy or muddy pools and backwaters. Feeding adults are usually found attached to other fishes in large rivers, lakes, and impoundments. They migrate upriver to spawn in gravel riffles and runs. (Ref. 3221, 10294). Described as anadromous in Ref. 51243. Larval stage lasts for about 4 to 7 years (Ref. 1998, 10294). Metamorphosis occurs in November, in Michigan. Duration of adult stage 12-13 months in Québec (Ref. 89241). Adults are parasitic for 1 to 2 years. Semelparous (Ref. 1998). In Ohio, the spawning period is from 26 April to 2 June. In Michigan, the spawning period is from 23 May to 26 June, at water temperatures between 12.8-22.8 ?C, with peak spawning activity in early June. Nests are built in streams having 3.5-30 m width, 10-61 cm depth, and 0.1-4.2 m3/s flow. A nest can be 30-cm in diameter, open on the downstream side, 8-15 cm deep, and it can also contain sticks and twigs. Up to ten spawning lampreys have been found in a nest. Fecundity, 10,800 eggs/female. Spawning occurs during daylight hours and into dusk. There are reported occurrences in Michigan of communal spawning of Silver Lamprey with Northern Brook Lamprey (Pine River), of Silver Lamprey with Sea Lamprey (Carp Lake, Devils, East Au Gres, and Rifle rivers), and of Silver Lamprey, with Sea Lamprey, and American Brook Lamprey (Carp Lake River). In the Laurentian Great Lakes Basin, it has been negatively affected by control measures directed towards Petromyzon marinus, except for the chemosterilization of males, which affects only the latter species (Ref.89241).