Freshwater Sharks

When we hear the term freshwater sharks, most of us are likely to assume that it refers to the shark species which live in freshwater sources, that is, in rivers. While that is true, many people use this term to refer to some species of bony fish which are not at all related to sharks. The list of true freshwater shark species include the Bull shark and the River shark, whereas other species, which are commonly referred to as small freshwater sharks, include species such as Bala shark and Roseline shark.

True Freshwater Sharks

In marine biology, true freshwater shark species are species which inhabit various river bodies on the planet. This group includes two of the most popular members of the shark family - the Bull shark (Carcharhinus leucas) and the River shark (Glyphis). While the Bull shark is found in freshwater sources spanning across tropical areas, River sharks are restricted to fresh and brackish water sources in Asia and Australia.

Bull Sharks
The bull shark is considered to be one of the most aggressive shark species in the world. An adult male in this species can grow on to attain a length of 3m and can weigh around 500 lbs. These sharks inhabit rivers and shallow waters of the ocean in the tropical areas, as a result of which, their chances of coming in contact with humans increases significantly. Being apex predators in their natural habitat, these sharks feed on a wide range of marine lifeforms, including different types of fish, turtles, mollusks etc. Their amazing ability to survive in saline as well as freshwater sources makes them one of the most fascinating creatures of the marine biome. Bull sharks are enlisted as 'Not Threatened' species by the International Union for Conservation of Nature (IUCN).

River Sharks
The River shark is an umbrella term for five subspecies of sharks which inhabit the rivers of Asia and Australia. These shark species are relatively rare, and thus have become one of the most sought after animal species of the marine world. The five subspecies of River sharks include:

• Ganges shark (Glyphis gangeticus)
• Northern river shark (Glyphis garricki)
• Speartooth shark (Glyphis glyphis)
• Irrawaddy river shark (Glyphis siamensis)
• Borneo river shark (Glyphis sp. B)

The International Union for Conservation of Nature (IUCN) has declared the Irrawaddy river shark, Northern river shark and the Ganges shark as 'Critically Endangered', while the Speartooth shark has been included in the list of endangered sharks. The Borneo river shark is yet to be described scientifically, and therefore most of the information available about this species is based on sightings.

A large number of people actually refer to freshwater cyprinids when they say freshwater sharks. Cyprinids are small bony fish species which are quite popular when it comes to aquarium fish trade. These species are also referred to as 'sharkminnows' or simply 'sharks'. Some of the most popular members of this family of fish include the Bala shark, Epalzeorhynchos, Labeo, Roseline Shark, etc. Owing to their colorful appearance and docile nature, these species are quite popular among fish keeping enthusiasts.

More recently, the existence of freshwater sharks has become a subject of raging debate among marine biologists in the world. While several sources classify Bull sharks and River sharks as freshwater species, other sources are of the opinion that these species are actually marine sharks which have the ability to travel upstream and survive in freshwater. That, however, doesn't change the fact that true sharks are different from freshwater cyprinids.