Yes, QUAHAUG is a Scrabble word!

Letter values in Scrabble US: Q 10, U 1, A 1, H 4, A 1, U 1, G 2.

Is it a valid word?

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

Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes
an edible American clam; the heavy shells were used as money by some American Indians

Also: hard-shell clam, round clam, hard clam, venus mercenaria, mercenaria mercenaria.