what is the worlds biggest fish?

Depends which angle you are coming at? Whale shark are protected so a useless fish to target if you are an angler. I myself would say the world's biggest fish to a keen angler would be a Black Marlin. Now that's a serious fish. But you may not be an angler and i've probably just given you a useless bit of bias information. Cheers.

The Whale Shark, Rhincodon typus, is the largest of all fishes. Whale Sharks between 4 m to 12 m in length are most often seen, but this species can possibly reach a length of 18 m.

Whale Sharks can be easily recognised by their colour pattern. The ventral surface is whitish, and the back and sides are blue to blackish with white stripes and blotches. They have prominent ridges on the side of the body with the lowermost expanding into a keel on the caudal peduncle

But, I thought sharks were not fishes and I saw an episode of Monster quest about Monster fish that had a vietnamese catfish at over 10ft long and 900 lbs.....also Aligator Garr are said to exceed 10ft long.

The whale shark is the biggest species of fish. If you want to see one, if you are ever in the Atlanta Georgia area, they have a few in the aquarium there. It is truely a spectacular sight. (at this time the Atlanta aquarium is supposed to be the biggest in the world, but I am sure that will change soon)

The worlds biggest fish is indeed the whale shark

Great white sharks get to be more like 5,000 pounds for anglers. Whale sharks are the biggest fish period. Mola Mola is the biggest bony fish. Sharks of course have cartilage based skeletons, not bones.

The worlds biggest fish is a whale shark.It is actually a shark and not a whale.

Whale Shark.

http://en.wikipedia.org/wiki/Whale_shark

whale shark however the oarfish is about 55ft long making them the second biggest fish and the coolest

megalondon