Yes, DOLPHINFISH is a Scrabble word!

Letter values in Scrabble US: D 2, O 1, L 1, P 3, H 4, I 1, N 1, F 4, I 1, S 1, H 4.

Is it a valid word?

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

the lean flesh of a saltwater fish found in warm waters (especially in Hawaii)
large slender food and game fish widely distributed in warm seas (especially around Hawaii)