Grand dent-chien

This is a hunter, and it looks the part. The grand dent-chien is one of the freshwater barracudas, a slim, hard-jawed fish that eats nothing but other fish. It reaches 30 cm and 255 g. It is widespread rather than rare, and it tends to hold in water with a steady, moderate flow rather than in still corners.

Also known as: red tail barracuda, spotted cachorro, red tail cachorro, freshwater barracuda

Several slender silver predators share these rivers, and a fast fish in tea-coloured water gives you one look at best. Take that look at the tail base. This species carries a black mark there that is unusually deep for its size, at times running across nearly the full depth of the narrow part before the tail fin. A slim predator with a clean tail base, or only a faint smudge, is not this fish. Together with the shoulder mark, the pair settles it.

The body is long and lean, built for a fast chase, and the jaws carry the kind of teeth that give the group its name. The clearest marking is on the shoulder, just behind the gill cover: a dark spot shaped like an oval or an upside-down teardrop, deep enough to take up a good part of the body's height at that point.