Spawning of the Anadromous Alewife, Alosa pseudoharengus, in Bride Lake, Connecticut

During 1966 and 1967, the spawning runs of an anadromous population of alewives, Alosa pseudoharengus (Wilson), were studied in Bride Lake, Connecticut. Alewives entered the lake from Long Island via Bride Brook from March to June. The number of fish entering the lake each day varied and was not related to water temperature or amount of moonlight. Males predominated among early migrants, whereas a 1:1 sex ratio existed through the later part of the migration. The average size of adults decreased as the migration progressed. Adults spent from several days to 3 months on the spawning grounds, the males outnumbering the females. Counts of the number of fish entering and leaving the lake indicated that high mortalities occurred. Females spawned from 48,000–360,000 eggs. The total number of eggs spawned in the lake was estimated to be 2.0 X 1010. Young alewives migrated seaward from June to October and increased water flow was thought to be a major stimulant. One young alewife migrated seaward for every 80,000 eggs spawned, i.e., a 99.9987% freshwater mortality of eggs and young occurred. The ratio of young fish produced to the number of females spawning in the lake was 2.88:1.