In our last edition ofAquaBytes, we introduced the unpleasant and invasive Snakehead fish. Now here’s another aquatic oddity to send shivers down your spine: freshwater sharks. There are indeed shark species that survive and thrive in rivers and lakes around the world, including right here in the U.S.
The most prevalent species of shark found in freshwater is the bull shark. There is also a group of rare species found in the Eastern hemisphere collectively known as “river sharks.” All of the so-called freshwater sharks are actually marine sharks; although they may live for long periods in freshwater, studies indicate that they return to the ocean to breed. Still, give the freshwater sharks some credit: that any marine shark is able to survive in freshwater for an extended period is a remarkable feat of adaptation that involves taking in (and excreting) water at 20 times the rate of a typical marine shark1.
Bull sharks tend to stick to coastal areas – they’re regularly found in brackish Lake Pontchartrain in New Orleans – but have been documented as far north on the Mississippi River as Alton, Illinois. Anecdotal (and unproven) stories of bull sharks abound: in Lake Michigan in Chicago; under a frozen lake in Minnesota; and even in downtown Albany, Georgia, via the Flint River. It is believed that the infamous Jersey Shore shark attacks of 1916, one of which occurred in a creek 16 miles inland, were perpetrated by bull sharks (although a great white got the credit in “Jaws,” the book and movie inspired by the incidents).
No need to stop swimming in rivers, lakes and ponds, though. Bull shark attacks in general are statistically rare, and rarer still in freshwater bodies. And our man-made neighborhood impoundments are certainly shark-free.
1Viegas, J. “Freshwater Sharks: Big Fish Where You Least Expect Them.” Discovery Shark Guide. 2010.
