A river shark, as far as is known, is a species of shark that lives in freshwater rivers. All six known river shark species belong to the genus Glyphis, which is part of the Carcharhinidae family. River sharks remain one of nature’s great mysteries; only a handful of river sharks have been captured and few have been observed in their natural habitat. Scientists assume that, due to rare sightings, most species of river sharks are likely to be endangered.
As members of the Carcharhinidae family, river sharks share many of the same characteristics as their oceanic relatives. They have small, round eyes and the upper teeth are wide and serrated. Its nose is short and rounded, with wide-set nostrils. They also have a prominent dorsal fin. They are the most similar to whale sharks, which belong to the genus Carcharhinus. The whale shark has a lower set of teeth that protrudes even when the jaw is closed, and a second dorsal fin that is almost half the size of the other dorsal fin.
In all, there are six documented species of the Glyphis genus: Glyphis gangeticus, better known as the Ganges shark; Glyphis glyphis, known as the Speartooth shark; Glyphis siamensis, known as the Irrawady River Shark; Glyphis species A; Glyphis species B, also known as the Borneo River Shark; and Glyphis species C. The Ganges and Irrawady sharks are named after the rivers in which they were documented. Glyphis river shark species have been documented in several rivers in Australia.
Very little is known about the ecology and habits of river sharks, due to rare sightings and scarce documentation. It is presumed that river sharks are primarily fish eaters, although this is not known for sure. Nothing substantial is known about their breeding habits.
Sightings are so few and far between that, at one point, the Ganges shark was not sighted for about a century. Officially documented sightings of the Speartooth Shark are even rarer. River shark species are considered endangered and some, such as Speartooth and Irawaddy, possibly extinct – although it is very likely that such sharks may have been seen but confused with other river shark species.
The bull shark – also from the family Carcharhinidae – is sometimes confused with a river shark. Bull sharks have been known to swim for miles in freshwater streams, where they can live for years. The bull shark’s main habitat and only breeding ground, however, is the ocean.