Even in the most biodiverse rainforest of the world, the pirarucu stands out: It can weigh up to 200 kilos (440 pounds), by far the largest of 2,300 known fish species in the Amazon. It nearly vanished from the Medio Jurua region not so long ago as illegal and unsustainable fishing swept the lakes with large nets. Now, something remarkable has happened. The fish has come back to the lakes of Medio Jurua, thanks to sustainable fishing practices by riverine communities and Deni Indigenous people.