Q: Canned tuna fish is sold in western countries and usually represent a perfect
solution for many Muslims there when they fail to find halal meat. Question: Is
it allowed to eat tuna fish cans when it is impossible to know whether it died
after taking them out of water?
A: For scaled fish to be halal one should be certain that a human being took it
out alive from water and it died outside water; otherwise, eating it is
impermissible. In this ruling, there is no difference between canned tuna fish
or other kinds of fish. However, if it is imported from Muslim countries, it is
ruled to be halal. Also, if one doubts as to whether it has scales or not, it is
apparently ruled as halal unless the opposite is known.