Ecosystems

Rivers have been the lifeblood of human civilization throughout history, and yet we know surprisingly little about what lives in many of them – including the giant creatures that prowl their depths. While we know the biggest animal in the ocean is the blue whale and the largest marine fish is the whale shark, the identity of the world’s largest freshwater fish species long remained a mystery. Until 2022, that is, when fishers in Cambodia caught a giant freshwater stingray in the remote reaches of the Mekong River. Weighing an astounding 661 pounds, the stingray surpassed by 15 pounds a giant catfish caught in Thailand in 2005 that had previously been considered the unofficial record holder. The discovery marked a milestone in fish biologist Zeb Hogan’s more than two-decade quest to study and protect giant freshwater fish. As a group, these megafish are among the most endangered animals on the planet. The world’s largest fresh...