The Collaborative International Dictionary of English v.0.48:

Mykiss \My"kiss\, n. [Russ. muikize, prob. fr. a native name.]
   (Zool.)
   A salmon (Salmo mykiss, syn. Salmo purpuratus) marked
   with black spots and a red throat, found in most of the
   rivers from Alaska to the Colorado River, and in Siberia; --
   called also black-spotted trout, cutthroat trout, and
   redthroat trout.
   [Webster 1913 Suppl.]