Raw tuna fish can be eaten raw without needing to cook it first.
The raw tuna is actually considered more healthy for you than cooked tuna is and raw tuna contains more Omega 3 fatty acids which is good for your brain health.
However just be aware that when you eat raw tuna or any other types of raw fish that there is a potential for bacteria to be present in the raw tuna or raw fish you eat.
So on a slim chance you could get sick from bacteria that could be on the raw fish.
Cooking the tuna or any other fish kills off any potential bacteria so that you do not get sick.
Tuna is best eaten cooked and tuna that is in cans that you buy in the stores is cooked tuna and ready to eat or serve.
But you certainly can eat raw tuna if you want too.