Yes, SKIPJACK is a Scrabble word!

Letter values in Scrabble US: S 1, K 5, I 1, P 3, J 8, A 1, C 3, K 5.

Is it a valid word?

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

oceanic schooling tuna of considerable value in Pacific but less in Atlantic; reaches 75 pounds; very similar to if not the same as oceanic bonito
medium-sized tuna-like food fish of warm Atlantic and Pacific waters; less valued than tuna
able to right itself when on its back by flipping into the air with a clicking sound

Also: skipjack tuna, euthynnus pelamis, atlantic bonito, sarda sarda, click beetle, snapping beetle.