Yes, TUNNIES is a Scrabble word!

Letter values in Scrabble US: T 1, U 1, N 1, N 1, I 1, E 1, S 1.

Is it a valid word?

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

important warm-water fatty fish of the genus Thunnus of the family Scombridae; usually served as steaks
any very large marine food and game fish of the genus Thunnus; related to mackerel; chiefly of warm waters

Also: tuna fish.