How long does tuna stay edible after being opened from the can?!
Answers: Assuming it's been refrigerated.
Taste trumps edibility in this situation. Tuna taste fairly decent for about 3-4 days after it's been opened. As long as there's enough liquid, and no other contamination, it can be edible for 7-10 days (in optimum conditions, twice this time, but most likely your fridge doesn't qualify as 'optimum'). But it won't taste great.
Tuna in cans have already been cooked, so their fridge life is not that short.
I worked in a deli a few years ago and we pulled everything after four days. Same with tuna. I think you would be pushing your luck if you ate it after four days. The thought of eating spoiled tuna is enough to make you sick!