I would presume so however the flavoured ones may have a bit of sugar.  For memory I think, lemon pepper and the lime and pepper ones don't have any or little sugar as per the John West webiste http://johnwest.com.au/our-range/tuna/tuna-tempters/tuna-tempters-lemon-and-cracked-pepper-95g their lemon and cracked pepper tuna has no sugar in the ingredients.