The whale shark is the largest fish in the world. This is a bit confusing because it is a fish, not a mammal, which the whale is. This list enumerates other large fish that exclude the shark, which would otherwise dominate it.
1. The Ocean Sunfish
The Ocean Sunfish is the largest and heaviest species of bony fish. The largest one ever caught measured more than 10 feet long and topped the scales at almost 5,000 pounds! The average weight of the ocean sunfish is around 2,000 pounds. They have bony skeletons, setting them apart from cartilaginous fish. Their huge eyes and relatively tiny mouths lend them an almost surprised look, though considering their size, any other creature would be surprised to find this mountain of a fish hovering near them.
The scientific name of the ocean sunfish is Mola mola, derived from the Latin word for millstone, in reference to the fish’s disk-like shape. Interestingly, the ocean sunfish does not have a tail. In its place is a clavus, an appendage that is a combination of anal and dorsal fin rays. Despite being tail-less, however, they are capable of leaping out of the water.
The ocean sunfish lives in tropical and temperate waters and can be found virtually anywhere: in the Pacific, Mediterranean, Indian, and Atlantic Oceans. True to their name, they are often seen lying sideways on the surface of the water, sunning themselves. This is most probably to re-heat themselves after taking a long, cold dive in the ocean depths foraging for food. Speaking of which, their food of choice is jellyfish, though the menu expands to accommodate salps, mollusks, plankton, small fish, algae, and brittle stars.
Despite being built like a house, the ocean sunfish is not dangerous to human beings. They are slow movers and would be more likely scared of us. As for culinary uses, they are not touted to be good food in many places, though they are considered to be delicacies in Japan and Taiwan.
2. The Giant Cambodian Stingray
The Giant Cambodian stingray is endemic to South-east Asian and northern Australian river systems. They are critically endangered in Thailand; their population is threatened by human activity, such as construction of dams and siltation. They are bottom feeders, foraging river- and lake beds They can reach up to 1,320 lbs (600 kg). The largest specimen ever caught came up to over 16.5 feet or 5 meters long. These carnivores have not changed much in over millions of years. They are flat and wide, with a long and whip-like tail, causing them to be alternately called whiprays. They lie in wait beneath the sand and silt of riverbeds, stalking their prey with sensors that detect the electrical activities of other animals.
Unless they are attacked or manhandled, stingrays are not dangerous to humans. Their whip-like tail has a stinger that will pierce human skin and may introduce toxins into the body.
3. The Pirarucu
The Pirarucu is a native of the Amazon. Found in the tropics of South America, this fish embodies what the Amazon essentially is: untamed and ruthless. It is legendary how the Pirarucu can leap out of the water to grab at small birds hovering in the trees. These carnivores also feed on catfish and piranha, so they are also basically cannibals. They can grow to 10 feet long and tip the scales at 400 pounds. The largest documented pirarucu came in at 15 feet or 4.6 meters.
This giant of the Amazon has a bony, flat head and a long, scaly body with a stumpy and short tail. Its head is a greenish copper that progresses to a dark blue-green in the body then wanes to white at the belly. The tail fins are reddish.
Amazon natives, brave people that they are, catch the fish and find a variety of uses for its parts. They dry the scales and use them for sandpaper; the tongue is used as grater, and the meat is served up in a delicacy called Arapaima.
4. The Mekong Giant Catfish
The Mekong Giant Catfish is an herbivorous fish that can live up to 60 years old. It can grow to more than 10 feet (3 meters) and weigh up to 650 pounds (295 kg). They feed off of the flora and algae of the river. It is an endangered specie and is endemic to the Mekong River in South-east Asia. This scale-less freshwater catfish is teetering on the edge of extinction, with only a few hundred adults of the species left.
5. The Beluga or European Sturgeon
The Beluga or European Sturgeon the largest European freshwater fish. Although it can grow up to 16 feet long on average, the largest one ever measured tipped the scales at almost 7,000 pounds and gauged to be around 26 feet long. They are found mostly in the Adriatic, Black, and Caspian Seas of Europe. They are carnivores, feeding on anchovies, Gobi, flat fishes, Black Sea whiting, as well as molluscs, crustaceans, birds, and seals.
The truly amazing thing about Beluga Sturgeons is that they are functionally immortal: meaning, they do not age. They are slow growing and late to maturity, but do not die of old age. They can live up to more than a century, the oldest documented one being 118 years old, though many may have lived past that age.
Their greatest threat is the caviare industry. The caviare is the Beluga Sturgeon’s roe, and is worth more than $7,000 per kilogram. It is no wonder then that in the past 60 years, the Beluga Sturgeon population has fallen by 90%. It is extremely endangered and measures have been put in place to prevent poaching and sale of Beluga caviare.