The Collaborative International Dictionary of English v.0.48:

Gwiniad \Gwin"i*ad\ (gw[i^]n"[i^]*[a^]d), n. [W. gwyniad a
   whiting, the name of various fishes, fr. gwyn white.]
   (Zo["o]l.)
   A fish (Coregonus ferus) of North Wales and Northern
   Europe, allied to the lake whitefish; -- called also powan,
   and schelly. [Written also gwyniad, guiniad,
   gurniad.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Powan \Pow"an\, Powen \Pow"en\, n. (Zool.)
   A small British lake whitefish (Coregonus clupeoides, or
   Coregonus ferus); -- called also gwyniad and lake
   herring.
   [1913 Webster]