Some people are very surprised to learn that there is such a thing as freshwater sharks. Of course, most of the world’s shark species are found in the ocean, but there are some elusive and not so elusive sharks out there that can be found in freshwater. Granted there are only two types and possibly only five or six species of freshwater sharks, but they do exist and at least one is quite dangerous.
Bull sharks can be found in fresh water, typically in rivers or near warm shores in tropical areas. However, it has been observed that these animals are not strictly freshwater sharks. Some of them spend all of their time in fresh water, while others swim to salt water for mating and birthing. They are able to transition between the two because they have the ability to control the amount of urea and sodium in their bodies. They also urinate frequently to rid themselves of excess fresh water.
Bull sharks are medium-sized sharks that are grey on their top half and white on the bottom. They have short, blunt noses that they have been known to head butt their prey with before attacking. They weigh between 200 and 500 pounds and can grow to be 8 feet long. On average they live about 16 years. Their diet consists of just about any meat that swims near them, so humans should be very weary in areas where bull sharks have been sighted. Bull sharks are one of the three most dangerous shark species in the world to humans.
River Sharks
River sharks are some of the most elusive and rare fish species on Earth. There is not a lot known about them. For the most part, their diet, mating habits, populations, behavior, life expectancy, specific locations and size are all mysteries. It is believed that they eat fish, though not enough research has been done on them to know for sure. They are also believed to spend their entire lives in rivers, making them the only true fresh water sharks in the world. To date, there are only five known species, two of which may actually be one and the same. Of the five known species of river sharks, the speartooth river shark and the New Guinea river shark may be the same. The other three species include the Ganges river shark, which is critically endangered, the Bizant river shark and the Borneo river shark.
So you see, there are freshwater sharks in this world. They are not very common, with the exception of the bull shark which is relatively common, but they do exist and they are very interesting creatures. In the case of the bull shark, one can only marvel at its adaptations and avoid its aggressive behavior. In the case of river sharks, we can only hope that we will be able to obtain more information about these creatures in the future.
Sources
Fishin’ for Facts: River Sharks, retrieved 9/15/09, whatetimes.org/riversharks.htm
Bull Shark, retrieved 9/15/09, animals.nationalgeopgraphic.com/animals/fish/bull-shark.html
Fresh Water Sharks, retrieved 9/15/09, absolutepredator.com/Freshwater-Sharks.html
