I think it might be the climate of the last 40 years. Mercury is building up in tuna, and if you eat it, it will build up in you too. Strike one. Weren't the Evil Tuna fisherman also catching and killing Flipper in their tuna nets? Strike two. Now, folks don't have can openers (that is a good one, I have 2). Strike three.
A good tune fish sandwich, celery, seasoning, finely minced onions, lots of mayo...one fine sandwich! Gotta be Albacore though...