Yes, WHITEFISHES is a Scrabble word!

Letter values in Scrabble US: W 4, H 4, I 1, T 1, E 1, F 4, I 1, S 1, H 4, E 1, S 1.

Is it a valid word?

WHITEFISHES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any market fish--edible saltwater fish or shellfish--except herring
flesh of salmon-like or trout-like cold-water fish of cold lakes of the northern hemisphere
silvery herring-like freshwater food fish of cold lakes of the northern hemisphere