The biggest fish in the ocean is the Rhincodon typus or whale shark. Despite their tremendous size and intimidating appearance, whale sharks are commonly docile and approachable.
The largest species is the beluga sturgeon (Huso huso) of the Caspian and Black seas, the only extant bony fish to rival the massiveness of the ocean sunfish.
The basking shark is the second largest fish in the world, and like the largest fish (the whale shark) and the largest animal (the great whales), basking sharks are filter feeders that eat tiny, planktonic prey.
The Murray Cod is Australia's largest freshwater fish. The biggest recorded was 1.8m long and weighed 113kg!
#1 Whale Shark
The Whale shark, who is not a whale at all, but the world's biggest fish. The largest fish in the world is the whale shark. This species can weigh up to 21.5 tons and grow to be 41.5 feet long. In addition to being the largest fish, it is also the largest living nonmammalian vertebrate.
Most sources believe that the fastest species of fish is the Indo-Pacific Sailfish, Istiophorus platypterus. According to Johnson and Gill (see below) the species has been clocked in excess of 110 km/h (68 mph) over short periods.
The biggest fish in the ocean is the Rhincodon typus or whale shark. Despite their tremendous size and intimidating appearance, whale sharks are commonly docile and approachable.
Geography. The Tasman Sea is 2,250 km (1,400 mi) wide and has an area of 2,300,000 km2 (890,000 sq mi). The maximum depth of the sea is 5,943 m (19,498 ft).
Stonefish are the most venomous of all fishes. They are found throughout shallow coastal waters of the northern half of Australia. The fish usually lies motionless, often partially buried in the substrate and perfectly camouflaged among surrounding coral, rocky reef, rubble, or aquatic plants.
Red Handfish (Thymichthys politus) are found only off south east Tasmania and until last week only one remaining population of around 20-40 individuals had been identified.
Salmon is called the king of fish. With its steely, silver skin, as shiny as King Arthur's armor, it even looks the part.
While the whale shark is certainly a big animal, it is considerably smaller than the blue whale, Balaenoptera musculus, which is the biggest animal in the world. The largest blue whale ever recorded measured a staggering 33 metres in length.
The dwarf seahorse (Hippocampus zosterae) is a species of seahorse found in the subtidal aquatic beds of the Bahamas and parts of the United States. It is threatened by habitat loss. According to Guinness World Records, it is the slowest-moving fish, with a top speed of about 5 feet (1.5 m) per hour.
Sturgeon are the largest of the freshwater fish. The beluga sturgeon in Russia is the largest freshwater fish in the world. The white sturgeon is the largest freshwater fish in North America. White sturgeon have been reported to reach lengths of 15-20 feet and weights of nearly one ton.
It is estimated that the Leedsichthys species is found to be approximately 16.5m long, which is quite larger than the average Megalodon.
When it comes to size, the blue whale dwarfs even the largest megalodon estimates. It's believed blue whales can reach a maximum length of 110 feet (34 meters) and weigh up to 200 tons (400,000 pounds!). That's more than twice the size of even the largest megalodon size estimates.
megalodon was not only the biggest shark in the world, but one of the largest fish ever to exist. Estimates suggest it grew to between 15 and 18 metres in length, three times longer than the largest recorded great white shark.
Its white flesh is tender and tasty, it can measure up to three meters long and weigh more than 200 kilograms: meet the pirarucu, one of the world's largest freshwater fish, and native to the Amazon.
Flying fish can be up to 18 inches (45 centimeters) long, but average 7 to 12 inches (17 to 30 centimeters). There are roughly 40 species of flying fish. Flying fish are tropical and temperate marine species that can be seen off both the Atlantic and Pacific coasts of the United States.
Sperm whales have been cut open to reveal entire sharks and squid that had been swallowed whole, as well as other flotsam. Their jaws aren't designed for “chewing”—thus, they are adept at swallowing whole prey. So it is certainly possible that they could swallow an entire human (as this Smithsonian article points out).
#1—Blue Whale
Coming in at #1… the blue whale! Not only is the blue whale the largest animal to live on the Earth today, they are also the largest animal to have ever existed on Earth. A blue whale can grow up to 100 feet long and weigh upwards of 200 tons.