Among the fish populations that could be harmed by the Xayaburi dam in Laos is the critically endangered Mekong giant catfish, considered by the Guinness Book of World Records to be the world’s largest freshwater fish. The fish, which grows to 650 pounds and about 10 feet long, is only found in the Mekong River. It is migratory, moving between downstream habitats in Cambodia upstream to northern Thailand and Laos each year to spawn. Some experts fear the Xayaburi dam could block the migration and drive the giant catfish to extinction. (Photo by Courtesy of Zeb Hogan/University of Nevada, Reno)

A trainer tries to convince a dog to jump over an obstacle during the Dog Olympic Games in Rio de Janeiro, Brazil, Sunday, September 18, 2016. Owner of the dog park and organizer of the animal event Marco Antonio Toto says his goal is to socialize humans and their pets while celebrating sports. (Photo by Silvia Izquierdo/AP Photo)

To most of us, hand-feeding crocodiles might sound like a one-way ticket to a watery grave. But for Jose Eduardo Chaves Salas, 32, coming within inches of the fearsome creatures’ razor-sharp teeth is all in a day’s work. He runs Jose's Crocodile River Tour on the Tarcoles River in Costa Rica, where tourists can watch him feed crocs up to 17 feet long. Photo: A tour guide shows a thumbs up as he sits on top of a crocodile on the Tarcoles river in Tarcoles, Costa Rica. (Photo and caption by Barcroft Media)

An Indian boy dressed as Hindu god Shiva to attract alms from devotees chats with tourists as they sit on benches partially submerged in flood waters on the banks of the River Ganges in Allahabad, India, Thursday, July 30, 2015. The Ganges, one of India's largest rivers is flooded following monsoon rains. (Photo by Rajesh Kumar Singh/AP Photo)

Indian mourners perform a cremation on the roof of a building overlooking The Manikarnika Ghat in Varanasi on August 23, 2016. India's holy city of Varanasi has been forced to halt cremations along the banks of the sacred river Ganges as deadly floods from monsoon rains hit parts of the country, an official said. More than 100,000 people have been forced from their homes in recent days in northern Uttar Pradesh and neighbouring Bihar states as rain-swollen rivers burst their banks. (Photo by Sanjay Kanojia/AFP Photo)

Angler Thomas Rielly catches a fish during the opening of the salmon fishing season on the River Tay January 16, 2012 in Kenmore, Scotland. A procession with a pipe band and anglers made its way through Kenmore at the east end of Loch Tay to mark the start of the 2012 salmon season on the River Tay. (Photo by Jeff J. Mitchell/Getty Images)

Jensen a two-year-old False Map turtle, from the Mississippi River, gets used to his new home at Blackpool Sea Life Centre on February 13, 2012 in Blackpool, England. (Photo by Christopher Furlong/Getty Images)