Friday, November 18, 2011


Alosa pseudoharengus
The Alewife is a member of the herring family that was originally found off of the Atlantic Coast. Though they are still exist in that range, over the last fifty years they have become an invasive species in the Great Lakes.

In the 1950s, Alewives used the Welland Canal in Ontario to get around Niagara Falls and enter the Great Lakes. Around that same time, Sea Lamprey also invaded, killing off many of the large prey species that would have normally consumed the Alewives. Lack of predation allowed the species to spread, and they are now most abundant in Lake Michigan and in Lake Huron.

Though they are still abundant in the Great Lakes, the population is more in check than it once was. This is due to the introduction of predator species like stocked Trout and Salmon. Unfortunately, the Alewives still vie for food (mostly zooplankton) with other fish, and have negatively affected other populations because of that competition.

Atlantic Alewives are anadromous, a term that means the fish live at sea, but come into freshwater to spawn. Great Lakes Alewives obviously live their entire lives in freshwater, though they spawn in more shallow areas, depositing up to 12,000 eggs! The larvae hatch after only a week, and the fish can live 6 to 7 years.

IUCN Status : Not Listed
Location : North America
Size : Length up to 6in (15cm)
Classification : Phylum : Chordata -- Class : Actinopterygii -- Order : Clupeiformes
Family : Clupeidae -- Genus : Alosa -- Species : A. pseudoharengus

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