Photo Gallery: Megafishes

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.