Salmo oquassa

from The Collaborative International Dictionary of English v.0.48

Blueback \Blue"back`\, n. (Zool.)
   (a) A trout ({Salmo oquassa}) inhabiting some of the lakes of
       Maine.
   (b) A salmon ({Oncorhynchus nerka}) of the Columbia River and
       northward.
   (c) An American river herring ({Clupea [ae]stivalis}),
       closely allied to the alewife.
       [1913 Webster]