Spawning occurs in spring (most areas) or summer. Late summer spawning was observed in Carp River, eastern Lake Superior (Noltie and Robilliard, 1987, Can. Field-Nat. 101:599-600). Eggs hatch in 10-12 days. Larvae leave nest after around three weeks. Larvae burrow in sand and silt bottom in quiet water downstream from spawning areas and filter-feed on plankton and detritus. Larval stage lasts up to several years. Larvae metamorphose in summer and fall, move to the ocean or a lake, feed on fish carrion and as parasites on other fishes for 20-30 months, return to streams to spawn, then die.