The payara, also known in the fly fishing community as vampire fish, Hydrolycus scomberoides, is a species of dogtooth tetra. This predatory fish is found in the Amazon Basin in tropical South America. It was the first of four species to be described in the genus Hydrolycus.
The most noticeable feature of H. scomberoides is the two long fangs protruding from its lower jaw. These are used to impale their prey, mostly smaller fish. It typically reaches an average length of about 30 cm (1.0 ft), but can reach up to 51 cm (1.7 ft). There are reports of far larger individuals, up to 1.17 m (3.8 ft) in total length and 17.8 kg (39 lb) in weight, based on records by IGFA, but this likely involves confusion with the related H. armatus.
Although the fangs on Payara look like they would be used to spear its prey, they are generally used to trap the fish until they are able to position themselves to swallow the fish whole, head first. Of course, if they are feeding on bigger fish, such as piranhas they will at times use their fangs to rip their prey into smaller pieces for consumption. They like clear, fast-moving water with lots of currents. You’ll often find it in churning rivers and at or near the bottoms of waterfalls.