Zeb Hogan was already familiar with the legendary Mekong giant catfish. After all, he’d been studying the beasts, which grow to hundreds and hundreds of pounds, for years. But when a colleague in Thailand phoned him up in 2005 to say that fishermen had hauled a 646-pounder ashore, it seemed…unprecedented. So Hogan, a biologist at the University of Nevada, Reno, did some poking around. He found some records that showed that it was not only the biggest Mekong giant catfish, but the biggest recorded freshwater fish ever caught.
And it all got him thinking: Could there be even bigger freshwater fish out there? National Geographic apparently thought it was a good enough question to fund him, so cash in hand he set out to find the answer. On over 50 expeditions across six continents so far, Hogan’s been wading through river after river and hooking giant fish after giant fish—building a better picture of Earth’s little-understood freshwater monsters in the process. So far that 646-pound catfish stands as the world’s biggest, but in his quest Hogan has found that the picture he’s built ain’t pretty.