Hit the Hot-Spots
FEW DIVERS ARE ANY LONGER subject to that irrational fear of sharks incited by a sensation-seeking media. Of course, people do get bitten from time to time but not as often as they get attacked by hippopotami!
WHITETIP REEF SHARKS(Triaenodon obesus) are normally the first species of shark encountered by divers. This is simply because they are often seen resting during the daytime, lying calmly on a sandy bottom, pumping oxygen-rich water past their gills. They lethargically swim away only once the diver approaches closely.
Whitetips sometimes lie passively in groups, even on top of one another, and swim with a pronounced sway to their bodies. They have a white tip to the first dorsal fin, the upper lobe of the caudal fin and sometimes the second dorsal fin too. Although they can grow as long as 2m, they usually tend to be much smaller.
However, the big ones are often mistaken by divers for other species. Their slim rubbery bodies are ideal for searching for the sleeping fish and invertebrates they find tucked away among rocks and crevices at night. It is at this time that the frenetic activity of these relentless hunters can be witnessed.
Whitetip reef sharks are a pan-tropical species and are common in the Red Sea. But among the best places to see them hunting at night are Manuelita Island at Cocos, Sipadan island in Malaysia, where they feed on freshly hatched baby green turtles, and Maya Thila in the Maldives. They are not considered to be dangerous to man.
GREY REEF SHARKS(Carcharhinus amblyrhynchos) are commonly seen predators on almost every healthy reef in the Indo-Pacific region. They form a number of sub-species worldwide.
Rarely more than 2.5m long and usually a lot less, their combative display made when feeling threatened and often seen before making an attack has been well documented.
These sharks have a grey upper side with a white underside and often have a white marking along the tip and trailing edge of the dorsal fin. They can also have black tips to their other fins.
*They spend the daylight hours swimming in loose groups in deep water near to the reef, unless attracted in by the smell of easy pickings.
They can be reliably encountered from as far north as the Straits of Tiran in Egypt's Red Sea to the Maldives, Micronesia, Melanesia and Micronesia. Grey reef sharks are normally the stars of Scuba Zoo at Flinders Reef in Australia's Coral Sea.
*At Rangiroa, in French Polynesia, they are regularly seen being preyed upon by larger sharks. The passes at Bikini Atoll are well known for huge and relatively aggressive populations.
Mating season is when the weather is at its hottest. At this time females can be seen bearing severe injuries and scars from the biting attentions of the males. However, the females are equipped with especially thick skin to be able to tolerate such attention.
CARIBBEAN REEF SHARKS(Carcharhinus perezi) are the Western Atlantic's equivalent of the grey reef shark. The males are similar in behaviour and size but have no markings on the upper side of their brown/grey bodies. Like many other sharks, they have white undersides and black tips to the undersides of their pectoral fins.
The females, at up to 3m long, can be much more massive and were at one time regularly confused with bull sharks. They tend to have a taller first dorsal fin than bull sharks and a smaller second dorsal fin, and comparatively large eyes.
On the other hand, they are sometimes seen lying on the seabed in the way that whitetip reef sharks do. Caribbean reef sharks are the sharks of the movies, because so many films featuring sharks have been photographed in the waters around the Bahamas. They look exactly as you would expect a shark to look.
???? Most of the dive centres in the Bahamas stage shark-feeding dives in one form or another and these give divers the opportunity to see these animals close up.
This has become a big business which, in turn, has given the sharks a protected status because of their alternative commercial value. To date, one dive centre alone has seen more than 60,000 client-divers enjoy these close encounters without injury. Nevertheless, these are dangerous animals and should not be touched or interfered with in any way by divers.
BULL SHARKS(Carcharhinus leucas) have been implicated in more attacks on man than almost any other species. This is because they like to frequent the shallow waters of river estuaries and harbours, so often come into close proximity to man where there is poor visibility. However, they less often come into contact with scuba-divers - for exactly the same reason.
Bull sharks can tolerate both sea water and brackish conditions. They tend to be massive, heavily built animals, their large girth combined with a more modest 3-4m length. They have a wide, triangular-pointed dorsal fin, no particular markings and very small eyes.
These sharks have a wide-ranging diet that includes mammalian carrion and seabirds. They often work in pairs, one feeding while the other rides shotgun, but appear to have no natural enemy other than man.
*Bull sharks can be encountered in both tropical and sub-tropical waters and there have been some recent problems with them injuring swimmers while chasing fish hooked by anglers along the beaches of Florida.
One of the most reliable places to see bull sharks close-up is early in the year at the Shark Beach, Walker's Cay in the Abacos, Bahamas. Around a dozen are drawn in by chumming the water while people snorkel among them.
*Sharks react very differently to dead fish being introduced into the water than they do to injured potential prey, which can induce frantic activity. It should be pointed out, however, that shark-behaviourist Dr Erich Ritter, one of those who organises such static feeds, was spectacularly injured during such an event.
SILVERTIP SHARKS(Charcharhinus albimarginatus) are the sharks of your dreams and possibly your nightmares. They are pan-tropical ocean-roving requiem sharks which feed on swiftly swimming open-water species such as bonito and tuna, and can be found from the Pacific coast of America to the Red Sea.
When they get older and more lethargic, silvertips may come into the reef to look for sting rays and may be seen with injuries caused by the ray's barb or other scars caused by collisions with coral during these encounters.
Many sharks have a slight silver or white tip to their dorsal fins, but silvertips have a very distinctive marking to their dorsal, caudal and pectoral fins, making them almost impossible to identify wrongly. Silvertips are invariably magnificent-looking animals up to 3m long with long, slender features.
At the Avitoru Pass in Rangiroa, silvertips are tempted in with dead fish tied to a coral head, and will closely accompany divers afterwards until they have swum back into a pass through to the lagoon. Other good places to see them include Mexico's Socorro Islands, Sha'ab Rumi and Angarosh Reef in the Sudan, the Kavieng region of Papua New Guinea and the Rowley Shoals in Western Australia.
The numbers of silvertips have been appreciably depleted by the activities of long-line fishermen, to which they are particularly vulnerable. Large specimens should be treated with caution.
SCALLOPED HAMMERHEAD SHARKS(Sphyrna lewini) are one of at least nine species of hammerhead and can be found aggregating in large numbers almost anywhere in the tropics where cool deep water meets the warm water of the vertical reef wall.
However, they are very skittish animals and such encounters tend to be fleeting. They are known for schooling around submerged seamounts but nobody is yet sure why they do this.
Scalloped hammerheads are easily identified by their broad flattened heads. These serve both as an aid to swimming, by giving hydrodynamic lift, and as an increased area for sensory organs such as the eyes and electro-receptors, which are used to detect prey that might bury itself in the sandy seabed. The sharks are rarely more than 3m long.
Good places for reliable encounters are where small fish act as barbers to their hosts, cleaning away parasites from their skin. These cleaning stations can be reliably found in places such as Cocos, Malpelo and the outer islands of the Galapagos. Other popular places include the remoter parts of the Red Sea such as the Brothers and Pfeiffer Reef, El Bajo in the Sea of Cortez off Mexico and Rasdoo Atoll in the Maldives.
Scalloped hammerheads should not be confused with the great hammerhead (Sphyrna mokarran) which tends to be solitary, rarely encountered by divers, and is one of the largest predatory sharks in the world.
BLACKTIP REEF SHARKS(Carcharhinus melanopterus) and BLACKTIP SHARKS (Carcharhinus limbatus) are the lightweights of the requiem shark world. The two species have been the subject of much confusion and often misinformation in guide books about sharks.
Blacktip reef sharks are an Indo-Pacific species noted for inhabiting shallow reef tops, and for their inclination to swim in the incredibly shallow parts of lagoons, hunting for fish and crustaceans. They are often seen with the top half of their bodies exposed to the air while chasing prey in this way.
???? One of the prettiest sharks, with characteristic black tips and white banding to their dorsal fins, and black edging to their caudal and pectoral fins, blacktip reef sharks rarely grow longer than 2m.
They are found in areas such as the Maldives, Australia, Melanesia, Micronesia and French Polynesia.
???? Some shark experts prefer to call this species the 'blackfin shark' to differentiate it from the otherwise similar blacktip shark, which is also found on reefs and is also non-pelagic. Blacktip sharks are a pan-tropical species which have less well-defined markings and tend to frequent slightly deeper water. Although usually less than 1.5m long, they can be bigger.
Blacktips are regularly seen in the Northern Red Sea. When the wreck of the Thistlegorm was first rediscovered it was home to a large number of them, though these have since moved away.
They are also often seen competing for food with much bigger sharks at staged shark-feeds (for example in the Bahamas), using their greater acceleration and manoeuvrability to keep themselves from being eaten or injured. Neither species is considered dangerous to man.
WHALE SHARKS(Rhincodon typus) are the biggest species of fish in the sea and are co-called because they feed by filtering the water for plankton and small fish in the same manner as baleen whales. Although they can grow to a massive 18m in length, they are very docile animals and those divers lucky enough to enjoy an encounter with a whale shark are invariably impressed both by its size and its approachability.
Whale sharks are unmistakable once a diver realises that he is not being overhauled by a small ship, and they are often affectionately known as 'spotty monsters'. They have broad flat heads and distinctive light spots and both horizontal and vertical lines on their grey bodies. They roam the oceans of the world in pursuit of their food source, nearly always swimming near the surface.
Some experts think that the Indian Ocean whale shark population has a definite anti-clockwise migratory pattern, so that the same sharks pass Exmouth in Western Australia, Thailand, southern India and the Seychelles but at different times of the year. However, a tagging programme has yet to prove this and still very little is known about the species.
You can also reliably see them in the Maldives at the beginning of the year, in the Red Sea and in the Sea of Cortez in the summer, and at Darwin Island in the Galapagos and Cocos Island at times when plankton levels are at their highest.
???? Young whale sharks are commonly seen in springtime in the Gulf of Tadjura, south of the Red Sea. In the height of summer the Gulf of Aqaba is often frequented by juvenile whale sharks, possibly some of the same animals that have headed north.
A separate community of whale sharks is said to live in the Pacific. These creatures often swim in the company of other smaller fish, including remoras or shark-suckers, which seem to use the pressure-wave made by the forward progress of the larger animal, and hide in its shade.
Kobias are dolphin-like fish which often assume the role of the whale shark's protector, chasing away larger predators. Optimal conditions for sightings include warm surface temperatures with cold water below, which cause upwellings of nutrients and high plankton levels.
NURSE SHARKS(Ginglymostoma cirratum) are probably the shark most often seen close-up by divers without recourse to baiting the water with food. This is because they spend the daytime resting on the bottom, often under overhangs of coral or rock.
Nurse sharks feed on small fish and crustaceans by finding them with their long barbells and literally sucking them out from where they might be hiding. Their power of suction is said to be enough to drag the flesh off a man's thigh, but luckily these animals are very sluggish and move away from divers only when under extreme duress.
However, there has been an unusually high incidence of diver-attacks recently - caused by the fact that divers often molest them.
The nurse shark's Latin name translates as the 'shark with the curly mouth'. Around 2.5m in length at a maximum, it is often smaller and easily recognised by its broad head, two large dorsal fins and a caudal fin that represents around one quarter of the whole body length.
Nurse sharks can be found in all tropical or warm temperate waters from the Western Atlantic to the Eastern Pacific, usually close to the seabed, lying in caves and often in groups. At one site in Cura?ao, divers hand-feed large nurse sharks and individuals often join the 'chumsicle feed' at Walker's Cay in the Bahamas, where other sharks appear to defer to them.
???? One should be aware that in Australia these animals (a sub-species) are known as tawny nurse sharks, to differentiate then from the very different grey nurse shark or sand tiger.
SILKY SHARKS(Carcharhinus falciformis) see divers more often than divers see them. That's because they make a habit of swimming below dolphins and other toothed whales, picking off injured fish or parts of fish that the dolphins drop during feeding.
Swim on the surface with schooling dolphins and your splashing will attract the sharks from below to see if you are injured and potential prey.
Silky sharks are so-called because, unlike most other sharks, they have a smooth skin surface. They are swift and agile predators and can grow to a fair size at more than 3m in length. A truly open-ocean species that is always associated with deep water, they also feed on fast-swimming pelagic fish such as tuna and bonito.
They can be recognised by their long, slim bodies and long, narrow pectoral fins and plain colouration. They have relatively small and rounded first dorsal fins.
Silkies can be encountered in warm temperate to tropical waters throughout the world where reef walls meet deep water. Until it was decommissioned and removed, a well-known location to see small silkies was the Autec Buoy in the Tongue of the Ocean between Andros and New Providence in the Bahamas.
But silky sharks are also reliably encountered at the deepwater reefs of the Sudan, in Cocos and the outer islands of the Galapagos. They are believed to be one of the most common open-water sharks worldwide.
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BASKING SHARKS(Cetorhinus maximus) are second only to the mighty whale shark as the largest fish in the sea. They are not tropical sharks. Measuring up to 10m long, they frequent the cold and temperate waters of the world, feeding on the rich planktonic soup that divers associate with poor visibility.
Although these animals make regular appearances near to the coasts of Cornwall and the Isle of Man in early summer, precious little is known about them and scientists can only guess where they go to in winter.
They cruise slowly through the water, cavernous mouths agape, skin covered in a foul-smelling mucous and often trailing long threads of algae from their long pectoral fins. They can be observed easily from the surface, with their high erect dorsal fins exposed to the air. They have long ugly snouts and gill slits which seem almost to encircle the whole head.
If you spot a basking shark from a dive-boat and want to see it while in the water, the most effective technique is to get the coxswain to slowly encircle the animal from a distance, dropping off snorkellers at regular intervals as he goes. The people in the water should then gradually swim towards each other, reducing the size of the circle. The shark will know you are there and turn away as it swims, moving in tighter and tighter circles as it does so.
Eventually the circle of swimmers will be sufficiently small to allow a good percentage to enjoy a close pass by the animal before it breaks out and continues on its way. It's a memorable experience!
There have been no recorded incidences of attacks on divers.