Yes, BLOWFISH is a Scrabble word!

Letter values in Scrabble US: B 3, L 1, O 1, W 4, F 4, I 1, S 1, H 4.

Is it a valid word?

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

delicacy that is highly dangerous because of a potent nerve poison in ovaries and liver
any of numerous marine fishes whose elongated spiny body can inflate itself with water or air to form a globe; several species contain a potent nerve poison; closely related to spiny puffers

Also: sea squab.

Not playable in Scrabble US: PUFFERFISH.