It is also reported from the St. Lawrence River. The landlocked form is common in Lake Ontario, Lake Erie, Finger Lakes area, Oneida Lake, Oswego River system, and Ballston and Round lakes. Sea-run alewives move up freshwater streams from the sea to spawn during the period from late April to early June. Spawning takes place in lakes and sluggish stretches of rivers above tidal influence. Landlocked alewives move from deep water to shallow beaches in lakes or move up streams to ponds to spawn in spring.
Females usually move to the spawning areas just before the males.
Spawning takes place at night in groups of two or three over a sandy or gravelly bottom. In less than a week, the young alewives hatch to begin feeding on minute, free-floating plants and animals. By fall, the young alewives make their way back to the sea or, in the case of landlocked populations, to the deep waters of lakes. Landlocked alewives reach an average length of about 6 inches when adults. They have been stocked in some waters specifically to provide food for trout and salmon.