What is the largest fish (by weight) in the world?

Fish is a layman's term. Sometimes it only means bony fish, excluding cartilagenous animals like sharks and rays. It is a heterogeneous group of aquatic, cold blooded, animals. Whales are definitely not fish . The whale shark is a shark, whether sharks are fish or not is up to the person.

Sorry but you're wrong sharks are fish , whales are mammals.

Sharks are not fish.

Player #2342698, This was definitely a trick question and I am pissed off!! You cost me a life!! You are bad!!

i forgot a blue whale was a mammal!! i just got too cocky and didnt think threw the answer!! Trick question anyway!!!