Bad tuna stinks.

You’ll know. The smell is the first and most obvious sign — if it hits you with a sour, ammonia-like, or extra fishy odor that’s stronger than usual, it’s done. Canned tuna has a mild smell fresh out of the can. That changes quickly once it turns.

Texture is the second clue. Fresh tuna should be flaky and moist, not slimy or mushy. If it feels slick between your fingers or looks like it’s breaking down into paste, toss it. Color can also shift — it goes from pinkish or light tan to grey or brown. Mold is rare but possible if it’s been sitting wet in the fridge.

Rule of thumb: you can store opened tuna in a sealed container for about two days max. After that, don’t gamble. Food poisoning from bad tuna is miserable.

When in doubt, throw it out.