AleWives: Alosa pseudoharengus

photo from VT DEC: http://www.vtwaterquality.org/lakes/htm/ans/lp_alewife.htm

    A member of the Herring or “shad” family, the alewife is native to the Atlantic Ocean but migrates and spawns in freshwater rivers and lakes.  Through its spawning habitat, alewives have been able to adapt to freshwater and have done so in the Great Lakes causing many ecological disturbances.

How to Identify Alewife 

-3 to 10 inches in length.

-Has a silvery, blue-green metallic luster to its scales

-Large black spot behind its gills

-Its lower jaw extends beyond upper jaw.

-Underside of its belly has a distinct serrated edge where scales from each side of the body meet and overlap.

Often used as bait by anglers, alewife were introduced to Lake Erie 1931, Lake Huron in 1933, Lake Michigan in 1949, and Lake Superior in 1954. Alewives are thought to have spread to the Great Lakes through surrounding canals, lakes, and streams between the lakes. In 1997, the first alewife was found in Vermont. After the initial spotting in southern Vermont, they were also found in Missisquoi Bay in 2003 and eventually in the main lake in 2005.

 photo from USGS: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=490

Alewife threaten the native species of Lake Champlain by altering zooplankton communities, competing with other fish for food, and feeding on native fish eggs and larvae. They also pose a threat to native fish populations such as Lake Trout and Atlantic salmon as the alewife do not provide them with vitamin B like their native prey does, resulting in reproductive failure.   

In 2008, widespread alewife die-offs occurred in Lake Champlain, confirming that large numbers are now present. Although the long-term impacts of alewives on the Lake Champlain ecosystem are not yet fully understood, biologists are concerned this invasive species will pose a major threat to native forage and game fish populations. 

Die-offs occur because alewives are sensitive to temperature change, experience increased stressed levels when spawning, and lack a food source in some winter months.  

2008 Lake Champlain Alewife Die-Off

University of Wisconsin Sea Grant Institute: http://www.seagrant.wisc.edu/Home/Topics/FishandFisheries/Details.aspx?PostID=362

Norah Carlos

Lake Champlain Basin Program. Aquatic Nuisance Species in Lake Champlain & the Basin. 2011.

http://www.lcbp.org/nuissum.htm#alewife
Marsden, Ellen. "Lake Champlain Alewife Impacts; February 16, 2006 Workshop Summary."

http://www.lcbp.org/PDFs/Alewife_Impacts_2006workshopsummary.pdf
Vermont Agency of Natural Resources. Watershed Management Division. "Alewife." 2003.

http://www.anr.state.vt.us/dec/waterq/lakes/htm/ans/lp_alewife.htm
University of Wisconsin Sea Grant Institute. "What causes alewives to die off in great numbers at certain times of the year?" 2011.

http://www.seagrant.wisc.edu/Home/Topics/FishandFisheries/Details.aspx?PostID=362