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BiologyFreshwater. Mainly associated with stable, high quality, coldwater habitats. Ammocoetes and adults are most abundant in clear, permanent, unpolluted, pool-riffle streams where sand-gravel substrates predominate and summer flows are 0.3-4,400 m3/s and summer water temperatures 14-22.5 ?C. In Michigan, ammocoetes have been reported in lentic habitats up to 450 m from the presumed originating stream, at water depths 1-16 m, where substrates vary from sand-silt, with or without detritus, to gravel-rubble-sand (Ref. 89241). Adults occur in gravel or sand riffles and runs of creeks and small to medium rivers with strong flow and usually clear water; ammocoetes in sandy or silty pools (Ref. 5723). Non-parasitic (Ref. 1998, 89241). Semelparous (Ref. 1998). Spawning adults can be found in streams or lakes. Larval life lasts 4.5 yrs or more based on length-frequency analysis. Diet of ammocoetes is organic detritus, diatoms (11 genera), and desmids (one genus). Metamorphosis occurs between mid-August and October in Tennessee. Duration of adult life is about six months. However, three reports (Manion and Purvis, 1971, Vladykov and Kott, 1980a, Cochran, 1997) of seven adults measuring 26.0-35.4 cm TL, exceeding the maximum reported larval length of 24 cm TL, have been interpreted as an indication in this species of facultative feeding, either parasitically or perhaps on fish eggs or organic detritus, in the adult stage. Between metamorphosis and spawning it spends most of its time hidden under stones. In Michigan, the spawning period is from 20 April to 26 June, at water temperatures between 6.7-20.6 °C, with peak spawning activity in early May. In Québec, peak spawning activity occurs at a water temperature of 17 °C. In Tennessee, the spawning period is in March and in Delaware, it is from 28 March to 4 April, at water temperatures between 6.8-12.0 °C. Nests are built in streams with gravel and cobble substrates having 1.5-18 m width, 15-61 cm depth, and 0.1?5.2 m3/s flow. A typical nest is 16 cm in diameter. Up to 14 spawning lampreys have been found in a nest. The sex ratio is usually 1:1 and there are no significant differences in the length and weight of spawning males and females. Fecundity, 1,327-5,185 eggs/female and relative fecundity, 274-531 eggs/g body weight. Egg diameter, 0.94-1.19 mm. Eggs are spherical, adhesive, and demersal with color from pale yellow to light green. Hatching occurs 2-3 weeks after fertilization. Average length at hatching, 2.6 mm TL. Mean length at age 1 is 38 mm TL. There are reported occurrences in Michigan of communal spawning of American Brook Lamprey with Sea Lamprey (Carp Lake, Pine, and Pentwater rivers), of American Brook Lamprey with Chestnut Lamprey and Sea Lamprey (Betsie River), and of American Brook Lamprey with Silver Lamprey and Sea Lamprey (Carp Lake). 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. Vladykov (1949) reported that in the province of Québec, Canada, ammocoetes were at the time extensively sold at $0.50 to $1.00 Canadian per dozen as bait for sportfishes (Ref. 89241).