“It’s very hard to imagine what’s going on beneath the water when you look at a river – but you have billions of fish making these epic migrations, some of the largest animal migrations on Earth,” said Dr Zeb Hogan, at the University of Nevada in the US.
The longest migration of any freshwater fish species is that of the dorado catfish, which makes a migration of 7,000 miles (11,000km), from spawning in the foothills of the Andes to feeding in the Amazon estuary and back again. The silver-gold fish themselves were incredible, said Hogan: “They get to about 2 metres long.”
