Swimming with sharks!
Hello! My name is Greg,
I started diving 8 years ago and as soon as I went in the water, I fell in love with the underwater world. It has a beauty and peace that can’t really be described until you are down there. Needless to say from that moment on I was hooked and for the next few years whenever I went away I made sure it was to somewhere I could dive.
Over my 8 years of diving, the most special moments in the ocean have been with sharks. I have been lucky enough to dive with many different species of sharks from small 30cm sharks to the largest shark and largest fish in the ocean, the whale shark!
Whale sharks reach around 14-16m when they’re fully grown. They are an amazing animal to dive with and every time you see one it’s just as special as the first time! Around three years ago I had had enough of constantly wanting to be diving when I was back at home, so I decided to make the ocean my office and move to a career in diving and conservation. I have worked as a Dive instructor, Free diver, Intern Manager and Shark Educator. In the last year I have been lucky enough to work directly on a research project assisting with the collection of data and supervising the shark dives with Free divers. The reason I am here today is to share some of that passion with you guys and show you why sharks are such special animals and why we need to act to avoid disaster.
Sharks - if they disappear, we disappear
Sharks are regularly seen as the enemy, the bad guy, the scary shadow lurking in the deep. But is that what they really are? Everyone knows we need to protect rhinos, tigers and pandas, but few people are aware that super-evolved top predators essential to the health of our oceans are being wiped off the planet. Sharks are out of our sight and therefore out of our mind.
Sharks are vital to the marine ecosystem. They have been keeping our oceans healthy for over 400 million years. Before dinosaurs walked on the earth, before trees grew on land, sharks were there, but soon they might not be there anymore. This could be disastrous for the oceans, and therefore disastrous for us. Sharks are keystone species. This means that they play a vital role in maintaining the biodiversity and health of their ecosystem.
A brilliant example of the vital role of keystone species is demonstrated in the video called Wolves Change Rivers. The video shows the amazing effect that reintroducing this keystone species back into the environment had on the ecosystem including increasing the biodiversity and stability of the ecosystem.
Like the wolves of Yellowstone, sharks also have enormous effects on their ecosystems.
Firstly, they maintain biodiversity by ensuring a single species doesn’t dominate and overpopulate within the ecosystem. Without sharks and other top predators, certain species in the middle of the food chain, without the sharks to hunt them, would experience uninhibited population growth, which in turn would cause the overexploitation and therefore population crash of the species further down the food chain. This is called a trophic cascade.
The removal of large sharks causing trophic cascades has been well documented and these can have a direct negative effect on fisheries in certain areas. For example, a long-established scallop fishery was forced to close due to increased predation of scallops by cownose rays. Due to the overfishing and therefore massive decline in numbers of large sharks in the area, the population of cownose rays could grow rapidly and unchecked, this consequently caused the rapid decline of scallops in the area due to the fact that they are the cownose rays main food source. (Journal reference: Science (DOI: 10.1126/science.1138657)) Simply put, less sharks meant more rays and more rays meant less scallops.
Secondly, apex predators ensure the health and genetic strength of the species in an ecosystem. By preying on the ill and weaker fish, they ensure not only that diseases do not spread across a whole species population, but also improve the gene pool of the species by allowing only the fastest and most resilient to survive.
The importance of sharks to maintain healthy marine ecosystems is without doubt. But how does this affect us? We don’t live in the sea; however, the oceans play a much more important role in our own survival than a lot of people realise. Earth is a rather misleading name for our planet given that over 70% of it is covered in water not earth, but I guess calling the planet ‘Water’ would get a bit confusing! Here are some quick-fire facts to put into perspective just how reliant we are on the oceans being healthy:
The oceans produce between 50-85% of the oxygen that we breath
They absorb at least 25% of all of the carbon dioxide that we produce through carbon emitting activities such as burning fossil fuels.
They absorb 90% of the heat that is produced by those carbon emissions.
That means that we not only need healthy oceans to prevent our Earth from overheating but we also need them to breathe!
Now, I imagine a lot of you are thinking “Wow, maybe sharks are important to the ecosystem! So why didn’t I know this before and why aren’t they better protected?” To learn more about why sharks don’t get the protection they deserve read my “Sharks - why are we scared?” blog that follows on from this one.
How can you help?
““In the end, we will conserve only what we love, we will love only what we understand, we will understand only what we are taught””
My first recommendation is to continue to learn more about sharks. Learn about their biology, about their behaviour, about their evolution. The more we know about these amazing animals, the more we fall in love with them and the more we will protect them! So, keep learning!
Tell other people, inform others about the importance of sharks to marine ecosystems, and encourage them to learn more so that they too will learn to love sharks and call for protection!
To understand more about why we fear sharks, my next blog will be about why they still have this negative reputation and why they don’t get the protection they deserve. Watch this space!