I saw a shark !! I saw sharks !! a pair of shiny gray fins slicing through the water. I became alarmed and immediately my heart rate jumped, I froze on the spot where I was standing on a rock, up to my waist in the water, not moving. The sharks, in perfect unison, rose again ahead of me, and this time I realized that the edge of their fins is dark. They’re swimming about 50 cm from each other, coming in my direction. I’ve been swimming in the area for three days now, snorkeling and enjoying each and every of the strange and wonderful creatures. I’ve no one to call for help – my parents are diving in the area and should be up soon. I decide to swim to the shore as quickly as I can, three, two, one . . . and again, in perfect coordination, the sharks change their direction and dive into the water, disappearing. I put on my mask and put my head into the water quickly, but saw no sign of the sharks, or of my parents!! I started worrying. I searched around, only fish, swimming lethargically around, trying to find food that has been caught in the flow. And then, bubbles of air rising from the depth of the water – how great! My parents return and I see my mother about 5 meters below me. I accompanied my parents through the water to the shore, while all the time examining my parents to make sure they’re not missing any body parts, while the air bubbles are rising and bursting and tickling my stomach. On the shore I told me parents excitedly about my frightening meeting and my worries about them.
Now, over 25 years later, I know that there was no danger at all except for a heart attack! The sharks were “Black Fin” sharks – an average size shark that doesn’t grow to be larger than 1.8 meters. It is a reef shark that is easy to identify because all its fins are black around the edges, and hence its name. Only the underside is white. It is not considered dangerous to humans, and while looking for other food (fish) they come into the waters of the Coral Reef and even above the reef during low tide. This is exactly what happened then on the Sinai coast, and I was sure that they had come there because of me, whereas,, in fact, it was because of me that they fled from an area they normally inhabit.
My second meeting with the rulers of the sea occurred about two years later. The Virgin Islands, where my father had been sent to work, became my new place of residence. When I completed my diving course I looked for a way to dive as much as possible. I met a local fisherman who fished while diving. When I asked if I could join him he hesitated, and said that I had no experience. I ran a persistent campaign to persuade him, and added that I had already swum with sharks at home, in the Red Sea. The fisherman laughed when I told him about my first meeting with sharks, but he agreed that the next day I could accompany him on his dive.
Happy and confident I went to prepare my diving gear, and presented myself at ten to six in the morning, the time we were to leave.
We sailed to one of the nearby islands, cast anchor and descended into the water. I didn’t pay any attention to the fact that the fisherman had brought with him a large piece of a barracuda fish.
It all happened fast, fast and immediate. We’d gone under with the fisherman leading and I behind him. Within minutes a yellow shark appeared, swimming in circles slightly above the sand in the direction of the fisherman. I tried to yell to him that there was a shark in the water but, of course, he didn’t hear me, but my shouting did make the diving regulator fly out of my mouth. Then the fisherman removed that same piece of fish flesh, and held it out towards the shark. I became frightened and nearly forgot to breathe; I replaced the regulator in my mouth while the shark started to eat from the fisherman’s hand. I looked around and, right next to me, there was a small cave; I went inside with only a small part of my head peeking out towards the fisherman. Then, there was shadow above me. I looked upwards and really froze – a huge tiger shark was passing above me and swimming in the direction of the fisherman. When he saw him, the large shark pushed the rest of the slice of meat towards the huge shark – which swallowed it whole, swam around for a while, and then disappeared. The fisherman motioned to me to come to him, but I was scared of going out into the open water, and it was only after the fisherman came to me that I got up the courage to leave the cave, swimming directly to the boat. I got into the boat with my diving equipment with no problem, which should have been difficult due to the weight of the equipment, but due to the actual circumstances I literally jumped out of the water on to the safe deck of the boat. The fisherman got out of the water after me, and told me to relax – while I started speaking with him in Hebrew which, of course, he didn’t understand at all, and he was smiling . . . a smile which spread over his entire face.
The first shark had been a Lemon Shark, a yellow-grey sand shark, the color frm which it gets its name. Its head is round and it lives in the region of the Coral Reef. It is usually up to 4 meters in size. It feeds primarily on fish that it hunts on the Reef. It is considered dangerous to humans, and is also considered one of the more ‘intelligent’ sharks.
The second shark was a “Tiger Shark”, which lives in the upper regions of the body of water. They can be up to 7 meters long, and are one of the more dangerous fish. They feed mainly on fish and marine mammals. Diving with the fisherman, Tarwa, was undoubtedly a dive that changed my life. Since then I have been fascinated by sharks, try to learn about them at every opportunity and am always looking for opportunities to dive with them. Over the years I dived another hundred times with Tarwa, and nearly every time we spotted sharks.
During my first dives with sharks I always felt that, by a miracle, I was saved from attack; I didn’t understand why they didn’t attack me but, slowly, I got to know them, their modes of behavior, their preferred foods, their body language and, most important of all, I learned to appreciate one of the most wonderful animals, albeit one of the most frightening.
It’s hard to speak of sharks without mentioning the film “Jaws”. This film brought a lot of money to its producer (Steven Spielberg) but resulted in global fear of sharks, which continues until now. After this film was screened the shark was perceived to be a marine monster lurking everywhere waiting for swimmers and divers, and feeding delightedly on us humans.
This film and others, without a doubt, are the primary reasons for people being afraid of sharks; for the most part, there is no just cause for this.
But the irresponsible hunting of sharks is real, and results in depletion of sharks in the world. Sharks have always generated frightening stories, legends, exaggerations, lack of knowledge, inaccuracies and of course fear. In truth, only part of that is justified.
Of all the animals that walk, fly, burrow or swim there are only few that have survived for the long term, and can be found in large numbers of shapes and sizes like the shark. The first evidence of sharks dated back two hundred million years. However, the most interesting shark lived 70 million years ago. This gigantic shark (Megaladon), was up to 30 meters in size! But like other huge prehistoric animals, it became extinct over time. This gigantic shark and others are the ‘forefathers’ of the sharks that live in current times.
There are 344 types of sharks that are divided into 8 species, ranging in size from 25 cm through 20 m (the whale shark). These can be separated into three primary groups: the sand sharks, the reef sharks, and the open water sharks. The sand sharks, which have flat bodies, live for the most part in sandy regions and, contrary to the other sharks which must constantly be swimming, the sand sharks are often seen laying motionless on the sand. Generally their mouths are suited to cracking invertebrates that live in the sand, and catching small fish off which they feed.
The Reef Sharks live in the Coral Reef region. These sharks are, for the most part, of medium size and fast, and they hunt their food by swimming quickly above and inside the coral reef, thus managing to surprise their prey. They are considered the ‘cleverest’ of the sharks. This group also contains the Lemon Shark (negaprion brevirostris) which I encountered for the first time at the Caribbean Islands. Professor Samuel Gruber from the University of Miami, who studied them for over 30 years,
is of the opinion that they are capable of making association and remembering, like laboratory rats. The Black Fin Shark also belongs to this group.
Open water sharks are the largest and fastest, and also include those that are a threat to man. These sharks must be constantly moving in order to breathe. They can be seen in the deepest waters, up to just under the surface level. They are excellent swimmers.
Sharks are fish that belong to the family of cartilaginous fish (chondrichthyes): the shark has a spine composed of cartilage vertebrae and not bone, unlike all other
fish (osteichthyes). As with fish, sharks also have scales, but these are placoid scales that are characteristic only of cartilaginous fish. The feel of a shark is smooth in the direction in which it swims, but against the swimming direction (from the tail to the head) the shark is very rough . . . the first sandpaper in the world was the skin of a shark! The natives in Hawaii were the first ones to use this.
The body of most sharks is perfect for swimming (hydro-dynamic) and it is not by chance that submarines and torpedo missiles are amazingly similar to the shape of sharks. Equipped with a tail, the sharks can swim almost unhindered by the water. The fastest shark of all is the Lamnidae Blue Shark (isurus oxyrinchus) which can reach a speed of 50 kph and more. This shark is also known as the ‘Mako’ shark.
In order to understand the behavior of sharks, one must first understand their sensory system. The sharks have the same senses as humans: touch, sight, smell, hearing and taste. Additionally, the sharks are equipped with another two senses, the sixth and seventh. The sixth sense is a sort of ‘distance touching’, thanks to two rows of holes, one on each side (the side lines). Though these holes the shark is able to differentiate waves of pressure that are created from the movement of other living creatures even from a distance of hundreds of meters. The seventh sense is a type of electro-sensor capable of distinguishing electric fields given off by all living creatures. In order to identify the electric fields the shark is aided by small apertures located in the front of the head, which are connected to special glands. These glands are called “Lorenzini’s ampullae”.
Sharks receive information from their sensory system and act accordingly. Mostly, sharks feed on sick and wounded creatures and thus their sense of smell, which is very well developed, can identify blood, the discharge of a sick or wounded fish, even at a concentration of one part per million. Another method that the sharks have of identifying prey is by the non-uniform way in which sick and wounded fish swim, which result in water movements that are identified by the side line of the shark as being potential prey. This feature of eating constitutes the importance of the shark to the marine world: while feeding on sick and injured prey the shark is cleaning the waters and acting like a ‘cleaner’. This is also the origin of the main problem between man and the shark – in most instances of attack the shark has become confused and wrongly identifies man as being an injured creature. These attacks are called “mistaken identification’ and usually, in an instance of these attacks, after the initial attack the shark realizes its mistake and disappears.
Of almost 350 different types of sharks, only a few of these are dangerous to humans. But most people are scared of all kinds of sharks, to the extent that they panic just at the thought of sharks. Without doubt the most recognized of all sharks is the Great White Shark (carcharodon carcharias), which is up to 5 meters long and has strong jaws that are filled with sharp teeth. In recent years, the Great White Shark has become rare, and has been declared as a protected species by many different countries.
Written by: Aviv Levi – The Scientific Director of the Underwater Observatory Park.