Common name: ALEWIFE
Genus, species: Alosa pseudoharengus
Family: Herring
Order:
Phylum: chordate
Place of Origin: Marine Eastern seaboard of North America
Date of entry: Late 1800s
Point of entry to the Laurentian Great Lakes: Welland canal
Transported by: this was thought to be an assisted migration aided by environmental modification
Current range: The Great Lakes, Atlantic Coast
Environmental Impacts:
There is now academic debate about precisely how the alewife got into Lake
Ontariobut it is likely that it migrated into the Great Lakes from the Atlantic
coast after the barriers to fish movement were removed by the construction of the Welland Canal and the Erie
Canal.
The Great Lakes population of alewife was held in check by the
large native predators such as the lake trout and the lake
whitefish. When the populations of native fish crashed due to
over-fishing and sea-lamprey parasitism, the alewife population
grew rapidly. The first alewife observed in Lake Michigan was in
1949. Fifteen years later more than 90% of the fish biomass in
Lake Michigan was alewife.
Juvenile alewife eat the same zooplankton as native species of
chub and juvenile whitefish. Of the seven native species of chub
only one survives today.
At the end of their life cycle the dead alewife wash up on
shore by the millions, forming piles on the beaches of the Great
Lakes.
In response to this problem the Coho salmon was introduced from the Pacific Northwest. The Coho are very successful predators of alewife. Now sportfishing for Coho is big business. Since the successful introduction of the Coho, several other salmonid alewife predators have been introduced as sport fish. In Michigan sportfishing is a $3 billion per year industry that depends on the survival of the alewife.
Everything you ever wanted to know about the ALEWIFE, (Alosa
pseudoharengus)
http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=490
Pretty pictures and basic info on the Alewife :
http://www.seagrant.wisc.edu/greatlakesfish/framefish.html