The giant freshwater stingray may be the world’s largest freshwater fish. It’s also cloaked in mystery. No one is sure how many giant stingrays are left, which habitats they prefer ...

Mussel shells provide living space for insects and plants, and empty shells serve as nesting sites for small fish like darters. Unfortunately, for all their allure, freshwater mussels are the most ...

This story appears in the April 2017 issue of National Geographic magazine. Hundreds of millions of people worldwide would lack their prime source of protein without freshwater fish. Yet the lakes ...