Sharks may not be a man’s best friend, however they are critically important to our survival. These apex predators are helping to keep the ocean healthy. And the ocean, my friends, is what makes the world go round.
Why we need sharks ?
As the most important ecosystem in the world, the ocean provides up to ⅓ of the global food production. It is our best ally against global warming, producing oxygen while at the same time, removing about half of the atmospheric carbon dioxide (also known as greenhouse). Finally, the ocean contributes to the control of our Earth’s temperature and weather.
Needless to say, if we were to fail our sharks, we would, in a word, doom ourselves. Now, this is how important saving sharks is ! Not about how it affects scuba diving destinations, not about how cruel shark-finning is, not about how magnificent these predators are : saving sharks is about saving our souls.
How do sharks help regulate the ocean ?
So how exactly are sharks keeping the marine ecosystem in balance ? Simply put : by eating !
Sharks can be found in all major oceans and seas. Furthermore, they are highly migratory, regulating the ocean everywhere they swim.
For one, at the top of the food chain, sharks eat a varied diet, therefore they keep all prey species in check. By doing so, they improve the biodiversity of the marine life. Indeed, these predators prevent overpopulation of one species over another. When things get out of balance in the ocean, there are cascading effects, some of them unexpected. We will see examples of the presence of sharks safeguarding the coral reefs and the quality of the sea bed.
In addition, sharks tend to feed on sick or weak preys stopping the spread of disease among fish populations. This is Survival of the Fittest at its best.
Let’s get real : real-life example of the impacts of sharks
Coral vs. Algae in Belize & Jamaica
Ripple effects are hard to predict. When it comes to sharks, there are a number of case studies offering insights into the impact of sharks on the ecosystem. In Belize, the overfishing of sharks led to the quick increase of one of their preys : the grouper. They like to feed off parrotfish, whose population got quickly decimated. These herbivorous fish graze on algae, keeping the coral healthy.
A similar chain of reactions caused the reef of Jamaica to become mostly algae-dominated in less than 20 years. The coral, unable to compete with the algae for space, now only covers 10% of the reef.
Removal of sharks led to a decline in scallops in the US
Downstream effects of the decline in shark population can be surprising. In the case of the mid-Atlantic states of the United States, it led to a decrease in the scallop fisheries. In these parts of the world, sharks fed mainly on cow-nose rays. With less and less sharks preying on them, the population of these rays skyrocketed. Guess what their favorite food is ? Scallops ! As more and more of cow-nose rays populated the area, the decline in scallops started to hurt the fishermen.
The role of tiger sharks in Australia
Tiger sharks in Australia impact the reef system by influencing the feeding patterns of their prey. Afraid of the presence of a predator, preys, such as herbivorous fish, dugongs and sea turtles will alter their feeding habits on a daily basis according to the number and location of sharks.
In this way, it prevents the seagrass plant from being completely eaten and destroyed by schools of hungry fish. Studies in Shark Bay, Australia, have found that the presence of tiger sharks in the area influences the quantity and quality of the seabeds.
Why are sharks endangered ?
Sharks are being overfished as a bycatch. They were not the primary target of the fishing nets, but got stuck in it anyway. Another culprit is, interestingly enough, a simple soup. This expensive Chinese delicacy creates an increasing demand for shark fins, killing up to 100 million sharks every year. Find out more about Shark Fin Soup, the controversy.