Sun, Sea and Suspicious Sharks

When travelling to the Bahamas on Field Course fortnight, I had one main aim, to get up close and personal with what some would argue is the world’s deadliest fish (which my mother strongly disapproved of!). The Great White Shark might come to mind, and those that travelled to South Africa were fortunate enough to see several of these 4m predators. However, the fish I was after is only half the size yet it possesses a secret weapon that no other shark in the Americas has, the ability to survive in fresh water. It is, of course, the Bull Shark.

How do they do this? Their secret lies in their kidneys and the fact they also pee a lot! By urinating 20 times more in freshwater than they would in saltwater, Bull Sharks are able to reduce the concentration of salt and urea in their blood allowing them adapt to various levels of salinity in their surrounding environment. This process is known as osmoregulation and it effectively prevents the Bull Shark from absorbing too much freshwater, swelling up and bursting like a water balloon.

So having travelled a grand total of 5,000 miles from Falmouth to Cape Eleuthera, where would 28 of Exeter’s best budding Zoologists find one of the Oceans most charismatic predators? Well luckily for us, the local fishermen feed a few in the local marina and it’s not just Bull Sharks that take advantage of these scraps, Nurse Sharks a member of the Ginglymostomatidae family, are also drawn into these feeding events.

With my GoPro attached to a pole, I dangled myself over the edge of the marina wall and filmed what happened when the sharks were drawn in by the fishermen. Now the Bull Shark may not be as big as Great White or a Tiger Shark, but that being said, the fishermen could have done with a bigger boat.

wjh205    January 25th, 2015    Bahamas archive