Yes, WOLFFISH is a Scrabble word!

Letter values in Scrabble US: W 4, O 1, L 1, F 4, F 4, I 1, S 1, H 4.

Is it a valid word?

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

large ferocious northern deep-sea food fishes with strong teeth and no pelvic fins
large elongate scaleless oceanic fishes with sharp teeth and a long dorsal fin that resembles a sail

Also: wolf fish, lancet fish.

Not playable in Scrabble US: LANCETFISH.