I don't see why not! Just watch the fact that tuna can be high in Mercury, but as long as you don't have it more than twice a week, I think it's fine. I could be wrong about the Mercury, so please do your own research, but it sounds like a wonderful snack!
I think that if it's nutritious and fits within your calorie range ... any food is a fine snack. I try to keep a couple of hard boiled eggs on hand or cheese that is already cut into one ounce pieces.