Mixing flax oil with tuna? Yecch . . .
Tuna's actually pretty tasty mixed with plain yogurt . . . mix it up like mayonaise, and it's not bad at all. Similar consistancy, similar flavor. Onions are good, too.
Sometimes a bit of barbecue sauce helps to break the monotony; I'll eat it right out of the can with a bit of bbq right on top.