Arapaima and Diver
A diver shares a tank with an adult arapaima fish at an aquarium in Manaus, Brazil. Known as the pirarucu in Brazil and the paiche in Peru, this South America giant is one of the largest freshwater fish in the world. Some reach lengths of more than 10 feet (3 meters) and weigh upward of 400 pounds (180 kilograms).
Large megafish like these have become rare worldwide due to heavy fishing. The arapaima is the focus of several conservation projects in South America, including no-fishing reserves and fishing quotas.
Tourists walk past a preserved paddlefish on display at the Yangtze River Fishery Research Institute in Jingzhou, China. This critically endangered species lives in China Yangtze River and is a contender for largest freshwater fish in the world. Unfortunately, overfishing and dam construction have decimated paddlefish populations. None have been seen in the wild since 2003, and scientists worry the species may already be extinct.
A pair of Chinese sturgeons swims in the Beijing City Aquarium in China. Capable of weighing half a ton and growing to 16 feet (5 meters) long, this freshwater leviathan is one of the largest sturgeon species on Earth. River damming in China has caused its numbers to plummet, and it is listed as an endangered species.
A boy poses with a giant barb on the Tonle Sap River near Phnom Penh, Cambodia. The fish, landed as bycatch by a local fishing operation, was tagged and released as part of a study of large freshwater species in the Mekong River Basin. There is evidence that giant barb once reached sizes of 10 feet (3 meters) long and 660 pounds (300 kilograms), but today specimens even half that size are extremely rare.
Man and Giant Barb
A Cambodian man grimaces as he comes face-to-face with a giant barb on the Tonle Sap River near Phnom Penh. Fishermen along the Tonle Sap catch five to ten adult giant barbs each year, making the region one of the last places on Earth to see these impressive fish at their largest.
Young Giant Stingray
A man holds a newborn giant stingray caught by local fishermen on the Banpakong River near Bangkok, Thailand. The mother stingray measured 14 feet (4 meters) long and weighed an estimated 200 to 300 pounds (90 to 140 kilograms). Scientists hope the presence of a baby and a pregnant mother mean the river is a nursery for these threatened freshwater giants.
One of the largest fish in the world, Mekong giant catfish, such as this one on a fisherman boat, can reach 10 feet (3 meters) long and weigh up to 650 pounds (300 kilograms). This critically endangered species has suffered from overfishing, dam building, and habitat destruction.
Mekong Giant Catfish
A Cambodian man observes a Mekong giant catfish on the Tonle Sap River. Fishermen captured this specimen, which weighed about 500 pounds (230 kilograms), as bycatch in a stationary bag net. It was later released.
Two boys lug weighty river catfish in Cambodia. Once a staple food in Cambodia, catches of these large, slow-maturing fish have dropped 90 percent in the past 20 years.
Giant Eurasian Trout
The giant Eurasian trout, also known as a taimen, is famous for its voracious appetite, dining on everything from fish to ducks to muskrats. This 5-foot (1.5-meter) specimen was found on the banks of the Eg-Uur River in northern Mongolia after choking to death on a 3-foot (1-meter) victim of the same species.