Managing Coastal Ecosystems
The Freshwater Shark: Bull Sharks and Their Movement between Fresh and Saline Environments
Carcharhinus Leucas or bull sharks are the only species of sharks that are able to travel long distances and spend extended periods of time in freshwater environments. Although many people disagree, I believe that one of the bull sharks’ main reason for entering freshwater is to find breeding grounds. There is evidence that supports this theory, and it seems to me a very logical explanation, however it is a controversial concept. In this paper, I will discuss what physical characteristics allow bull sharks to survive in both marine and fresh waters, and attempt to understand whether they do this for a purpose, or if they simply do it because they can.
Bull sharks got their name from their stocky shape, broad, flat snout and aggressive unpredictable behavior and their scientific name is Carcharhinus Leucas (Thomas H. Lineaweaver, and Richard H. Backus. The Natural History of Sharks). Bull sharks are common and can be found worldwide in shallow warm tropical and sub-tropical regions. They are renowned for their unpredictable and often aggressive behavior, and because they dwell in the same type of warm shallow waters we like to swim in, they can arguably be considered the most dangerous species of sharks to humans. What makes these sharks so unique and interesting to me, is the fact that they are able to thrive in both marine and freshwaters, making them even more of a threat to humans. There have been reports of bull sharks as far up river as Indiana in the Ohio River and in Illinois in the Mississippi River (www.publish.csiro.au). They are typically solitary hunters who roam shallow waters, and can use their strength to accelerate rapidly. Along with the great white shark and the tiger shark, it is considered one of the three species of sharks most likely to attack humans. Bull sharks have the highest testosterone...