powen

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]