Shark Attacks in Perspective
My sister and I were swimming in a quiet area of Jervis Bay on the east coast of Australia a few years back. Suddenly a fin cut through the water…another one appeared next to it and another and another. Moving fast, not towards us but very close. Sharks?
It turned out a pod of dolphins was cruising past and we were over the moon about having such a close encounter with these amazing mammals!
Since that day in Jervis Bay I have voluntarily dived with many different species of shark, including the giant Whalesharks, Hammerhead Sharks, Grey Nurse Sharks, White-tip and Black-tip Reefsharks, Port Jackson sharks, numerous wobbegongs and just recently I snorkelled up close with a Lemon Shark. And guess what, at each occasion I actually entered the water hoping I would be lucky enough to see sharks. I have lived to tell the tale. And yes, all my limbs are still there, intact and there wasn’t a moment I would have thought the outcome would be any different.
Plenty of people go through a lot of effort to dive or snorkel with Great White Sharks, Tiger and Bull Sharks - which are all considered to be dangerous to humans - in locations they are known to frequent. Snorkelling with Whalesharks, off Exmouth in Western Australia for example, is another well-known experience.
People are scared and fascinated at the same time by sharks and that comes a no surprise since shark live in a habitat that is relatively foreign to us and we are no where as gracious and fast moving as any animal living in the water. We are fairly restricted in our movements once we enter the water and can no longer touch the ground. In addition our vision is limited and once we are underwater for a while we will always have to come up to the surface where we bob around, helplessly. Sharks on the other hand are fast moving top-predators, fully adapted to their environment and mostly portrayed as indiscriminate killing machines. And a lot of their biology is still a big mystery to us land-dwelling mammals.
Background on sharks of the world
There are almost 1000 known shark species worldwide of which about 160 species live in the waters surrounding Australia. Most shark species can be found in the relatively shallow continental shelf areas at a depth between 0 and 200 meters.
Sharks - and their close relatives rays and chimeras - have a skeleton that is build up from cartilage rather than the bony skeleton of mammals and other fish. All species are cold-blooded. Fortunately, only a few of those species are considered dangerous to people since on occasion their presence in the water has a bad outcome for the people.
All known sharks are carnivorous, which basically means they don’t like their vegies. Their diet might consist of large fish including other sharks or shellfish and for some occasionally garbage that is floating past.
Sharks have been around a long time and generally speaking have well-developed senses of sight and smell. Their hearing is very different to ours, but their internal ears can detect vibrations and differences in pressure. In addition they have the so-called 'Ampullae of Lorenzini' located on their snout, which can detect fluctuations of the electrical fields in their surrounds. A combination of those senses is used in detecting and locating its prey.
Sharks come in a lot of different shapes and sizes. Sharks vary from looking like the classic shark such as the Great White Shark and the Bull Shark to something more friendly-looking like the Port Jackson or the Leopard Shark. The smallest shark known to man, the Dwarf Lantern Shark, has been estimated to grow to a maximum length of maybe 20 cm. The world’s largest shark, the Whaleshark, has been reliably reported to reach lengths of well over 10 meters. For some more info on a few species have a read of our article '11 Sharks you should know this summer'
Shark attacks in perspective
Any shark attack makes for a good story. Of course, any loss of human life or serious injury is a tragedy, but realistically your car trip to the beach carries a higher risk of being killed than you being killed by a shark once you get there and go for a swim or surf. And in the last 215 years of documenting shark-human incidents sharks have attacked less people than people killed by road crashes in Australia each year.
On average 1 person per year dies as a result of a shark attack in Australia compared to ~ 200 people per year who die due to accidental drowning, and ~ 2000 die in road crashes.
Personally, I get rather annoyed when another shark attack hits the headline and it turns out that someone has a bite on their arm after lifting a wobbegong shark out of the water by its tail.
To find out a little more about shark attacks have a read of article 'Shark Attacks - 7 answers to frequently asked questions'
Human Attacks in perspective
It is hard to say how many sharks are being killed by humans per year, but the number is in the millions – 100 million according to Sea Shepherd. Their population are indiscriminately depleted faster than they can reproduce. Two human actions stand out as being particularly cruel and unnecessary.
Shark finning is the practice of cutting off the fins of a shark. Shark fins are used in shark-fin soup or for traditional cures. Once the fins have been cut off, the shark still alive, wounded and helpless will be thrown back over-board and dies a slowly death as the shark is not able to swim. The rest of the shark is not valuable enough to justify transporting the relatively bulky shark body back to shore.
Besides the suffering of the individual sharks it has major consequences for the shark population, the marine eco system and loss of sharks as a food staple for many developing countries.
There are countries that have shark-finning legislation in place, even some that state the fins must be still attached, meaning it would be illegal to have only fins on-board.
And then there are the shark nets. According to Wikipedia a shark net is a submerged net placed around beaches to reduce shark attacks on swimmers. A common but debated practice in Australia. The Department of Primary Industry in NSW stated that the nets have never been regarded as a means of absolutely preventing any attacks, but help to deter sharks from establishing territories.
The nets are meant to capture sharks and prevent their escape until they eventually drown. But besides the sharks whales, turtles, dolphins, sea birds and even dugongs all die in beach nets too.