Life Cycle and Reproduction
As Alosa are generally anadromous, they are faced with various obstacles to survive. They may have to pass through numerous barriers and waters to get to either their spawning grounds or normal habitat (the sea in most cases). Estuaries are a major factor in numerous Alosa species migration. Estuaries can be highly variable and complex environments contributing to fluctuating biological interactions. There are shifts in osomolarity, food sources, predators, etc. Since many adult Alosa species die after spawning, it is the young who generally have to migrate to the sea from the spawning grounds. Duration of migration varies among fish but studies have shown that duration of migration can greatly affect survival.
Reproduction varies from species to species. Studies done on Alosa in Iranian waters have shown that spawning in Alosa varies in time, place, and temperature of the waters they inhabit.Fecundity may also vary.It is observed that species will spawn as early as April or as late as August. Temperatures range from approximately 11 to 27 degrees Celsius. Fecundity can range from approximately 20,000 eggs to 312,000 eggs. Eggs are pelagic.
The life span of Alosa can be up to 10 years but is generally uncommon as many die after spawning.
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