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BiologyFreshwater (Ref. 89241). Inhabit lakes and streams. Ammocoete larvae occur in pools and backwaters (Ref.1998). Ammocoetes more commonly found in firm, relatively stable, sand-silt substrate, in areas with current. Adults occur in still to swift water, clear to brown-tinged, over rocky and weedy substrates, to a maximum depth of 20 m. The usual habitat is large to medium-sized rivers with summer flows 0.8-31 m3/s and summer water temperatures 15.5-22 ?C. It can also occur in small to large lakes. Generally associated with warm water habitats and tolerant of variation in terms of discharge, water temperature, and substrate. Spawning adults only found in streams. Metamorphosis occurs in October, in Michigan. Adults parasitic on fishes (introduced Cyprinus carpio and native Catostomus commersonii, Ictiobus sp., Moxostoma sp., Esox lucius, Salvelinus fontinalis). Reported scavenging on Catostomus sp. In Manitoba, spawning behavior has been observed on 11-12 June at a water temperature of 16.5 °C and current velocity about 1 m/s. In Michigan, the spawning period is from 28 May to 25 June, at water temperatures between 15.6-22.2 ?C, with peak spawning activity in early June. Nests (up to 6.2 m X 1 m X 0.05 m) are built with stones 3.5-5 cm in diameter in streams having 6.5-43 m width, 38-90 cm depth, and 1.1-54 m3/s flow. Up to four spawning lampreys have been found in a nest in Michigan and about 50 in Manitoba. Eggs are elliptical with long axis 0.64 mm and short axis 0.56 mm on average. Eggs are preyed upon by Luxilus cornutus. There are reported occurrences in Michigan of communal spawning of Chestnut Lamprey with Sea Lamprey (Pine, Platte, and Muskegon rivers) and of Chestnut Lamprey with Sea Lamprey and American Brook Lamprey (Betsie River) (Ref. 89241). Adults ascend streams to spawn and die soon after egg laying is completed. Semelparous (Ref. 1998). In the Laurentian Great Lakes Basin, it has presumably been negatively affected by control measures directed towards Petromyzon marinus, except for the chemosterilization of males which affects only the latter species (Ref. 89241).