Yeah large fish come with large doses of mercury and other heavy elements that are bad for humans. At least you could get the tuna in pouches to further negate the effect of poisoning from the can as well.

Here's a warning from the folks at GoodHouseKeeping.com, with an apropos picture of a can of tuna:
http://www.thedailygreen.com/healthy...s-0330#slide-5

Though I'm being a debby downer here, as I could care less what I eat or how it's packaged most of the time.