Nerka \Ner"ka\, n. [Russ. niarka, prob. fr. native name.]

(Zo["o]l.) The most important salmon of Alaska (Oncorhinchus nerka), ascending in spring most rivers and lakes from Alaska to Oregon, Washington, and Idaho; -- called also red salmon, redfish, blueback, and sawqui.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Blueback \Blue"back`\, n. (Zo["o]l.)
   (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.

Source: Webster's Revised Unabridged Dictionary (1913)