In search of the world's largest freshwater fish – the wonderfully weird giants lurking in Earth's rivers
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.
- 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.
- The discovery marked a milestone in fish biologist Zeb Hogan’s more than two-decade quest to study and protect giant freshwater fish.
Colossal catfish and gargantuan gars
- Found on all continents except Antarctica, they are a wonderfully weird bunch of creatures, from colossal catfish and carp to gargantuan gars.
- But freshwater vertebrate populations have declined over the past five decades at twice the rate experienced by species within terrestrial or marine ecosystems.
- Megafish numbers in particular fell by a shocking 94%, according to one study of more than 200 large freshwater species.
What’s killing off the megafish
- The decline of giant freshwater fish is due to human impacts, such as overfishing, dam building and climate change.
- Since many of these species are slow to mature, they may never reach the age to reproduce.
- So far, however, conservation efforts to protect endangered giant freshwater fish species are mostly regional.
Alligator gars and sturgeon make a comeback
- But stricter fishing regulations introduced by Indigenous communities appear to have led to populations’ rebounding in many places.
- Today, alligator gar populations have bounced back in rivers like the Trinity in Texas.
Protecting the giants of the Mekong
- In an example of those efforts’ paying off, fishers in early 2023 caught a Mekong giant catfish weighing more than 200 pounds.
- While the record stingray is big, it might not be the largest of this species of ray in the Mekong.
- Research on the arapaima, for example, suggests it could grow as big, or even bigger, in places like Guyana.
- It’s about learning more about these amazing creatures to figure out how to better protect them.”