With all the flying fish, flying squid and flying plankton zooming through the air, it’s a wonder that anything in the sea manages to stay in the water at all. But it turns out that it isn’t just the oceans that are full of airborne acrobats – the fish in the rivers are at it too.

Say the word “flying fish” and you automatically think of the sleek, graceful, torpedo-like shapes that dart effortlessly out of the waves of the tropics and glide great distances. The association is very definitely marine, but there are freshwater flyers that are no less remarkable. The hatchetfish is one such specimen from South and Central America, and while its oddly-shaped, “front-heavy” shape might not seem particularly aerodynamic, its actually a trait that has specifically evolved to make flight easier.

Thanks to the enormously enlarged sternal region that gives it its name, the fish boasts large, stiff pectoral fins and the extraordinarily powerful muscles needed to power them. Taking up to one quarter of the fish’s bodyweight, the muscles allow the fish to actively flap its pectoral fins like wings, enabling it to power its way out of the water, and many a fishkeeper has found that it’s best to keep the aquarium lid on when keeping them in captivity.

Perhaps even more uniquely, the hatchetfish differs from other flying aquatic species because it flies in order to catch prey rather than to escape predators. With quick beats of its powerful fins, the hatchetfish is capable of snatching insects from the air simply by zeroing in on a target, leaping out of the water and snapping a hapless invertebrate in its jaws before splashing back down to enjoy a well-earned meal.

Thank you for reading this week's edition of FIN ('Fascinating Ichthyological Nugget'): the easiest way to propel your aquatic knowledge! We sincerely hope that you'll find these of interest and want to share them with your friends…