The Collaborative International Dictionary of English v.0.48:

Alewife \Ale"wife`\, n.; pl. Alewives.
   A woman who keeps an alehouse. --Gay.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Alewife \Ale"wife`\, n.; pl. Alewives. [This word is properly
   aloof, the Indian name of a fish. See Winthrop on the culture
   of maize in America, "Phil Trans." No. 142, p. 1065, and
   Baddam's "Memoirs," vol. ii. p. 131.] (Zool.)
   A North American fish (Clupea vernalis) of the Herring
   family. It is called also ellwife, ellwhop, branch
   herring. The name is locally applied to other related
   species.
   [1913 Webster]

WordNet (r) 3.0 (2006):

alewife
    n 1: flesh of shad-like fish abundant along the Atlantic coast
         or in coastal streams
    2: shad-like food fish that runs rivers to spawn; often salted
       or smoked; sometimes placed in genus Pomolobus [syn:
       alewife, Alosa pseudoharengus, Pomolobus
       pseudoharengus]