coregonus ferus

from 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]

from 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]