Bull Sharks are considered marine animals, often found in the seas and oceans. However, a recent study has found that a pair of these animals, scientifically called Carcharhinus leucas, managed to make their way to St. Louis by swimming up the Mississippi River in the United States. Published in the Marine and Fishery Sciences, the study sheds light on how this behaviour of bull sharks is not something new in their history, however, quite rare in Mississippi river.
The study was done by Cincinnati Museum Center paleontologist Ryan Shell, and Nicholas Gardner, a librarian at WVU Potomac State College with degrees in ecology and evolutionary biology. For their study, the duo went over hundreds of reports of sharks in the Mississippi River and compared those historical records with archaeological and paleontological evidence for bull sharks moving in those waterways in the distant past.
In the abstract of the study, researchers write that there have been rare incidents of bull sharks swimming into river systems and other freshwater ecosystems from five continents. The study has also found a wide geographic range of this phenomenon. The physiological adaptations of bull sharks also allow them to move into rivers. The duo also mention a fossil record in the Miocene Epoch which implies that this behavior has a long history. They also mentioned the two confirmed bull shark catches in the historical records. The first one took place in 1937at Alton, Illinois, and another happened outside of St. Louis in 1995.
However, the study observed that the lack of fossil evidence of bull shark in freshwater deposits indicates that the incidents of venturing into freshwater is a relatively recent development in their behavior. It is also speculated that the occasional ventures into the freshwater have been a habit of bull sharks for millions of years, but somehow, it has not been recorded in the fossil record.
The researchers concluded with saying that there needs to be more research done into the biogeography of bull sharks for a better understanding.