^Good post.
I'm aware of the mercury issue it is an issue for all fish , the higher they are in the food chain the worse, i was buying mercury-free ones already.
Radioactivity is something much more important and dangerous. Most tunas are supposedly fished and packed in Thailand but how can you be sure , and it's very close there too.
Canned tuna was my #1 source of food protein, easy to store, long expiry date , no cooking, no fat , no carbs, high percentage of good quality ( BCAA chain ) protein, it is actually a solid state protein supplement.
I recently stopped consuming them, but i am still not sure if all this tuna/fukoshima correlation is a fact or an urban legend / conspiracy theory...