Q: Canned tuna fish is sold in western countries and usually represent a perfect solution for many Muslims there when they fail to find ḥalāl meat. It allowed to eat tuna fish cans when it is impossible to know whether it died after taking them out of water?

A: if scaled fish is imported from a Muslim country or you are confident* that a human being took it out alive from water or it died in the fishing net, it is ḥalāl.
By being confident, it is meant that the opposite probability is so weak that the people do not take it into consideration.