The Collaborative International Dictionary of English v.0.48:

Blay \Blay\, n. [AS. bl?ge, fr. bl?c, bleak, white; akin to
   Icel. bleikja, OHG. bleicha, G. bleihe. See Bleak, n. & a.]
   (Zool.)
   A fish. See Bleak, n.
   [1913 Webster]