When people think about the world’s most threatened animals, it’s unlikely that Anguillid (freshwater) eels spring to mind. In Europe, freshwater eels are one of our least appreciated but most critically endangered species, having declined by around 95% since the 1980s. Unlike most people, as a freshwater ecologist, I spend a lot of time thinking about animals like the freshwater eel because globally, all freshwater species are facing considerable threats.
Killifish are a group of unusually small and colourful fish that have evolved particularly robust egg casings. These casings prevent the embryos from drying out and some species survive for months, even years in dry mud. This has allowed killifish to colonise and survive in the smallest temporary pools, even in an elephant’s footprint. The sudden appearance of fish in fresh puddles has given rise to the phrase ‘It rains fishes’.