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Arapaima and Diver
Photograph courtesy Zeb Hogan
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.
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Preserved Paddlefish
Photograph courtesy Zeb Hogan
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's 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.
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Chinese Sturgeons
Photograph courtesy Zeb Hogan
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.
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Giant Barb
Photograph courtesy Zeb Hogan
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.
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Man and Giant Barb
Photograph courtesy Zeb Hogan
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.
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Young Giant Stingray
Photograph courtesy Zeb Hogan
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.
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Giant Stingray
Photograph courtesy Zeb Hogan
Fish experts believe the giant stingray, such as this one in Cambodia's Mekong River, is the largest freshwater species on Earth. This specimen measured more than 13 feet (4 meters) long.
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Lake Sturgeon
Photograph courtesy Zeb Hogan
Once abundant in North America's Great Lakes and upper Mississippi River, lake sturgeon populations have plummeted. These freshwater monsters, the continent's largest fish, are extremely long-lived. Scientists determined that a six-and-a-half-foot (two-meter) specimen caught in Canada in 1953 was 152 years old.
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Giant Catfish
Photograph courtesy Zeb Hogan
One of the largest fish in the world, Mekong giant catfish, such as this one on a fisherman's 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.
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Mekong Giant Catfish
Photograph courtesy Zeb Hogan
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.
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River Catfish
Photograph courtesy Zeb Hogan
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.
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Giant Eurasian Trout
Photograph courtesy Zeb Hogan
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.
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Taimen Eggs
Photograph courtesy Zeb Hogan
Taimen lay their eggs in a nest called a redd, which is dug into the gravel of clear-flowing rivers. Baby taimen have many predators, but adults, which can grow to almost six feet (two meters) long, are kings of the river.
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Taimen Head
Photograph courtesy Zeb Hogan
The taimen is the world's largest salmonid. Some taimen reach six feet (two meters) long and weigh more than 220 pounds (100 kilograms). Once found over large areas of Russia, Mongolia, and China, the species is threatened by overharvesting and habitat destruction in most of its range.
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