Lake Nicaragua's Sharks
As a kid growing up in Canada, I visited Mara Lake in British Columbia with the family each summer, and every year, we’d be regaled with stories of the Ogopogo, a lake monster not unlike Scotland’s famous Nessie, that dwelled in the depths of the lake. Twenty years later, I no longer believe in the Ogopogo, but there is a different lake-dweller, equally mysterious and similarly shrouded in myth and legend, living nearly 7000 km southeast of where I grew up, in Lake Nicaragua – the Lake Nicaragua Shark.
Fifty years ago, before much was known about the marine life in the area, scientists believed that the sharks found in Lake Nicaragua were an endemic species, the Lake Nicaragua Shark. In the scientific community, the species was believed to be one of a kind – the only true freshwater shark that existed anywhere in the world. Scientists believed that the landscape had changed over time, slowly closing the Lake Nicaragua off from the Pacific Ocean, trapping the sharks.
In 1961, studies determined that the Lake Nicaragua Shark was, in fact, the common bull shark (Charcharinus leucus), a species known to exist in fresh water elsewhere in the world. Later studies proved that the bull sharks were able to transit the San Juan River by jumping upstream like salmon, ending up in Lake Nicaragua. Since the studies in the 1960s, the bull shark population in Lake Nicaragua has experienced a dramatic decline, believed to be due to silt build-up in the San Juan River, which makes it difficult for the sharks to swim through.
The bull shark, named for their stocky shape, broad snout and notoriously unpredictable and aggressive behavior, prefer warm shallow waters, and are often found near the mouths of rivers, and along coastal areas. Believed to be responsible for the majority of shallow water attacks on humans, bull sharks, along with the tiger and great white shark, are among the three species most likely to bite humans. The bull shark is a formidable creature, and must be treated with respect, but even so, the risk of attack is exceedingly low – to this day, there have only ever been seven recorded shark attacks in the country, three of which took place in Lake Nicaragua, with the earliest report dating all the way back to January 1950. Overall, the odds of getting attacked and killed by a shark are 1 in 3 748 067. In a lifetime, you’re more likely to die from fireworks (1 in 340 733), lightning (1 in 79 746), a car accident (1 in 84), stroke (1 in 24) or heart disease (1 in 5).