Freshwater Sharks  

Sharks are often regarded by many people as saltwater dwelling animals. Contrary to popular belief though, there are some sharks that are considered freshwater sharks. There are two types of sharks that are considered freshwater types, the bull shark and the river shark.  

Of the two types, the bull shark is by far more known. They are considered an aggressive type and may attack humans at the slightest provocation. The risk to humans is even more pronounced since bull sharks prefer warm waters that are shallow or close to the coast or shore. It is therefore inadvisable to risk taking a dip in a water region where bull sharks may have been sighted. Most people though wouldn’t even know that there are such creatures as freshwater bull sharks.  

Despite their label as freshwater sharks, bull sharks are not considered true freshwater creatures. This is mainly because studies have shown that these sharks travel from the sea to freshwater sources. Some of these sharks also travel back to saltier sections of water when they breed or give birth to their young. Once the young sharks are born, they can travel to freshwater sources themselves. Since they do not stay exclusively in fresh water, bull sharks are considered saltwater animals that are able to tolerate freshwater conditions.  

Bull sharks survive in fresh water by regulating the amounts of urea, sodium and freshwater in their bodies. They regularly and frequently excrete sodium and urea to make their bodies more adaptable to fresh water conditions. They also urinate a lot to get rid of the fresh water that enters their systems through osmosis. Some would suggest that the stress placed on the kidneys by this adaptive behavior push bull sharks to travel at regular intervals to salt water sources. There have been some bull sharks however that have been found residing in freshwater sources for many years without traveling back to saltwater regions. In fact, some bull sharks live the rest of their lives in fresh water after being born. 

As freshwater sharks, bull sharks have come to adapt to their situation in other ways. Since freshwater areas can change temperature and offer different or limited food sources, bull sharks grow no bigger than 7 or 8 feet.  

Unlike bull sharks, river sharks are considered true freshwater sharks. This means that these sharks have been found to have the ability to live and reproduce independent of saltwater regions. River sharks have not been known to cross over to the sea from their freshwater homes. River sharks are currently believed to live only in some parts of Asia and Australia. Among the identified types are the Irrawaddy, Speartooth and Ganges sharks. Unfortunately, not much is known both about these identified types and other unidentified ones. River sharks are considered very rare. One can only therefore make assumptions about these true freshwater sharks.  

Fresh Water Sharks are truly amazing creatures. After having survived for millions of years, they continue to adapt to their environments to promote continued survival. The bull and river sharks are proof of how resilient fresh water sharks can be.