Yes, HEADFISH is a Scrabble word!

Letter values in Scrabble US: H 4, E 1, A 1, D 2, F 4, I 1, S 1, H 4.

Is it a valid word?

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

among the largest bony fish; pelagic fish having an oval compressed body with high dorsal and anal fins and caudal fin reduced to a rudder-like lobe; worldwide in warm waters

Also: ocean sunfish.