Sharks of South Africa – Shark ID, biology and behavior.
Sharks of South Africa : Some ninety-eight species of sharks may be found in South Africa. Sharks, rays and skates all belong to the class Chondrichthyes (cartilaginous fish) – their skeletons being made up of cartilage, unlike those of bony fish. Sharks teeth, be they well defined or fused as plates, are continuously replaced throughout the animals life. Instead of swim bladders, sharks have large livers to increase buoyancy and store nutrients. All sharks are carnivorous and have a keen ‘sense of smell’ and are highly sensitive to vibrations and electrical impulses. Of the various species found off South Africa the majority are found in deep waters and are rarely encountered. Most species are harmless and only a few have been implicated in attacks on humans – mostly surfers and bathers – with only one recorded shark attack in South Africa on a scuba diver and that being on the surface.
WHALE SHARK – Rhinocodon typus.
Identification: Whale sharks are the worlds largest living fish, attaining lengths of 13m and weighing up to 13 tonnes. Once you overcome the initial fear of being in the presence of such an enormous shark several things should then become apparent. The huge, square and very wide mouth (thankfully the 3000 teeth in each jaw are minute and covered by a flap of skin) and the prominent ridging along the back, beautifully decorated with distinctive white spots and dashes – take a deep breath, relax and enjoy the show – see Mozambique dive tours.
Biology: Information is limited. The female produces live young (according to one reference as many as 300) from eggs attached to the uterus. Whale sharks, like the basking shark, are filter feeders, using their huge mouths to ‘vacuum’ zooplankton, squid and small fish which are then filtered through the sieve like structures inside the 5 large gill slits at each side of the head. It is believed that whale sharks only reach sexual maturity at 30 years of age or approx. 9m in length and that they may have a life span exceeding 100 years.
Behavior: Whale sharks occur in all tropical and warmer temperate waters and are highly migratory, their movements following plankton blooms and the changing temperatures of water masses. Preferring a balmy 21-25 degrees Celsius. Sightings in South Africa are more common in the summer months off the south coast of KwaZulu Natal, Sodwana Bay and Ponta Do Ouro Mozambique.
GREAT WHITE SHARK – Carcharodon carcharias.
Identification: Great white sharks are unmistakable. When you see one you’ll really know it. No other shark has such an awe inspiring presence. Sleek, silent (no soundtrack) and unquestionably in charge, the white sharks only predators are man and orcas. Great white sharks are believed attain 7m in length and weigh over 1800 kg. The body is robust and torpedo shaped, generally charcoal black to dark grey-brown on the upper half in distinct contrast to the white underbelly. The pectoral fins are long and large and black-tipped on the underside. The dorsal fin is prominent and the archetypal shark-fin shape. The caudal fin (tail) is one of the best means of identification, being sickle shaped and almost symmetrical – the only other shark in our waters with a similar tail is the shortfin mako (Isurus oxyrinchus). The toothy smile of the great white holds many large, triangular teeth with pronounced serrations on both upper and lower jaws.
Other names – Blue Pointer and Tommy shark – a grizzly reference to the fate of many British soldiers who went down with the HMS Birkenhead in 1852 near Gansbaai.
Biology: Little is known. Great white sharks are thought to be sexually mature at about 3.5m for males and 4 to 5m for females. Mating is probably a violent affair – if scars on females are any indication. The gestation period is thought to be between 14 to 18 months, and between 2 and 10 juveniles are born live at around 1.5m in length at birth. The life span of the great white shark is thought to be 30-40 years.
Behavior: Great white sharks feed on other sharks, seals, bony fish, turtles and large rays and dolphins, and are known to scavenge on dead whale carcasses. Surprisingly, recent research indicates that seals only comprise 20% of their diet. Great white sharks are universally feared, however they may often be wrongly implicated in attacks on bathers – especially in warmer waters where the Zambezi (bull) and tiger sharks are also possible candidates. Great white sharks can be found in all temperate and tropical waters worldwide. Often sighted close inshore, the larger sharks will seasonally congregate around seal colonies between extensive migrations. In February 2004 a tagged female white shark of 4m, named Nicole, surprised everyone with a transoceanic migration of over 11 000 km from South Africa to W. Australia. Nicole then completed the round trip in just over nine months when she was sighted again off Dyer Island, South Africa, in August 2004. Sightings of great white sharks in open waters off South Africa are rare, however a booming cage diving industry has developed around the seal colonies of Cape Town, Mossel Bay and Gansbaai.
SPOTTED RAGGED TOOTH SHARK – Charcharius taurus.
Identification: Ragged-tooth sharks are perhaps South Africa’s best loved sharks. Affectionately known as “raggies” to the locals, they may attain 3.2m and 300 kg. Ragged-tooth sharks have a plump, dark-brown to olive-grey body and a pale underbelly – the numerous dark spots fading with age. The fins of the ragged-tooth are thick and rounded. The first dorsal fin is well behind the pectorals and is only slightly larger than the second dorsal. The lower caudal lobe is undeveloped – ragged tooth sharks being relatively slow swimmers. The forehead slopes dramatically down to a pointed snout and mouth which bears the many long and pointed awl-shaped teeth – better for gripping than for cutting – that form the characteristic, ragged-tooth, overbite.
Biology: Female ragged-tooth sharks produce as many as 20 000 eggs which are retained in the uterus. As with all sharks, the males are easily distinguished by the large ventral claspers used to fertilise females. Seasonal scars on females indicate that mating may be a violent affair. During the gestation period of nine months, the first embryos to develop inside the uterus consume their own egg parcels. They then proceed to consume the remaining embryos and any unfertilised eggs until only two live juveniles emerge as live young – one from each branch of the uterus. After such fierce inter-uterine natural selection the young are then left to fend for themselves in the open ocean, often entering estuaries to escape predation.
Behavior: Ragged-tooth sharks migrate north from the Eastern Cape to mate in the warmer waters of KwaZulu Natal during the winter months. They congregate in large numbers and are an almost guaranteed attraction for divers at Protea Banks, Aliwal Shoal and at Sodwana Bay’s Quartermile reef. Despite their fearsome looks and size, the ragged tooth shark has never been implicated in any fatal attacks on humans. If threatened or harassed however, they are certainly capable of causing severe injury to swimmers and divers.
ZAMBEZI or BULL SHARK - Carcharhinus leucas.
Identification: Zambezi sharks may attain 3.5m. The body is predominantly grey with a lighter underbelly and no inter-dorsal ridge. The Zambezi is a robust shark with a distinctively rounded, blunt, snout. The teeth of the upper jaw are triangular and serrated, the lower jaw teeth are more slender. The fins are pointed and well developed without distinct markings. Fin tips may be darker in juveniles – fading with age. The Zambezi shark is often confused with the comparatively smaller Java Shark – Carcharhinus ambionensis
Biology: Zambezi sharks are remarkable in their ability to tolerate fresh water for long and possibly indefinite periods, having been recorded hundreds of kilometers upstream from temperate to tropical waters worldwide. Up to 12 young are born live in Summer after approximately one year gestation. They reach sexual maturity at about 6 years and a length 2.5m
Behavior: Aside from their freshwater capabilities Zambezi sharks are generally confined to coastal waters, estuaries and river mouths. They are opportunistic feeders, feeding on bony fish (50% of diet), turtles, small sharks and dolphins, rays and even crabs. The Zambezi (bull) shark has been implicated in many attacks on bathers and surfers worldwide, usually inshore and in murky waters. Often seen on Protea Banks, Kwazulu Natal, they are not regarded as a threat to divers, although they can be very inquisitive and deserve much respect. Tending initially to remain deep in a baited environment, Zambezi sharks may however be encouraged to move gradually closer, and with time, patient divers can be rewarded with increasing numbers and some spectacular encounters. Recent dives on Protea Banks have seen as many as 12 Zambezi sharks mixing freely with the divers – almost as if the divers are accepted as part of the pack. More on baited shark dives…
TIGER SHARK – Galeocerdo cuvier.
Identification: Another unmistakable submarine presence, tiger sharks are thought attain 7m in length, however sightings in South Africa are almost invariably of female sharks under 4m. The robust body bears dark vertical bars along the upper-mid-back, particularly evident in juveniles and fading with age. The snout is blunt and squared when viewed from above. The caudal fin (tail) is distinctively elongated on the upper lobe and is suited to slow cruising and only short, sudden bursts of speed. The first dorsal is prominent and linked to the much smaller second dorsal by an inter-dorsal ridge that also extends forward to the back of the head. Broad, serrated, cockscomb teeth are widely set in both upper and lower jaws.
Biology: Tiger sharks attain sexual maturity at around 3m and give birth to between 10 and 80 live young, measuring 50 to 90cm. Tiger sharks are relatively slow moving and like the ragged tooth shark are able to remain motionless for long periods by regulating water flow over the gills by means of active respiration.
Behavior: Widespread throughout temperate and tropical seas, tiger sharks are known to enter shallow coastal waters in the vicinity of large river mouths and harbors. A voracious and opportunistic predator, tiger sharks will feed on bony fish, smaller sharks, marine mammals and even birds. Tin cans, plastic bags and livestock have also been found in their stomachs – implying a tendency to scavenge. Recent research indicates that tiger sharks range extensively, covering large areas daily, often using a bouncing swim pattern of rapid ascents and descents through the water column to detect both benthic and pelagic activity as well as oils from floating or submerged carcasses. In July 2007 we witnessed approximately 15 individual tiger sharks feeding on the carcass of a dead whale - see full report on facebook. Periodically seen in the more tropical waters off South Africa, tiger sharks rarely investigate divers, tending rather to cruise past or shy away. Tiger sharks do however, respond well to baiting and can be encouraged to stay around divers in a baited environment. More on baited shark dives…
HAMMERHEAD SHARK – Sp. Sphyrna
Identification: Hammerhead sharks are unmistakable – for obvious reasons, although identifying exactly which species is another story. Nine species occur worldwide, three of which can be found in South African waters. The body is generally grey-brown dorsally with a lighter underbelly. Fins have no district markings. The eyes are located on flattened lobes each side of the distinctive hammer-shaped head. Teeth on both jaws are relatively small and serrated.
GREAT HAMMERHEAD – Sphyrna mokarran. The body is olive-brown above and lighter below, attaining up to 5.5m. The head is almost rectangular and notched front and center. The first dorsal is very long, elongated and prominent.
SCALLOPED HAMMERHEAD - Sphyrna lewini. The body is greyish above and paler below, attaining up to 4m. The front edge of the head being more noticeably scalloped in shape. The first dorsal is less prominent than that of the great hammerhead.
SMOOTH HAMMERHEAD – Sphyrna zygaena. The body is greyish above and paler below, attaining up to 4m. The front edge of the head being more smoothly convex in shape, lacking the central indentation found in both the scalloped and great hammerheads. The first dorsal is less prominent than that of the great hammerhead and more rounded than on either the scalloped or great hammerhead sharks.
Biology: Sexual maturity is attained at an approx. length of 2m – 2.5m. After about 6 months gestation the young are born live in litters of up to 40 in number. The uniquely shaped and highly sensitive head (swinging from side to side whilst swimming) gives these sharks a wider field of vision than any other shark and also seems a likely tool for detecting and catching prey hidden beneath the sand. Hammerhead sharks have been observed using the head quite literally as a hammer to stun prey. Stingrays, sand sharks, pilchards, anchovies and squid are all important to their diet.
Behavior: Found in all temperate and tropical waters worldwide, all species are assumed to be highly migratory. Adults are found offshore in deeper waters while juveniles are very common inshore from the Western Cape northwards during summer, often swimming just under the surface. Although relatively shy of divers and notoriously difficult to photograph, large specimens of great hammerhead and schools of several thundered scalloped hammerheads are seasonally encountered by divers on Protea Banks, Often found over the sandy bottoms favored by sand sharks.
SHORTFIN MAKO – Isurus oxyrinchus.
Identification: The shortfin mako is sleek and torpedo shaped, blue to grey dorsally and white underneath. The snout is sharply pointed. Fins are prominent. The tail is distinctively ‘sickle’ shaped and the pectorals are large. Sometimes mistaken for the great white shark, the most noticeable differences being a larger eye and sleeker body. while the teeth of the mako shark are longer, more slender and unserrated.
Biology: Shortfin mako sharks bear between 4 and 25 live young after 15 to 18 months gestation. 70 to 75 cm at birth, adults may attain almost 4m in length. Female makos become sexually mature at about 2.7m (17-19 years), while males mature at about 1.8m (7-9 years).
Behavior: Widely distributed, shortfin makos are found offshore and coastally in temperate and tropical waters, feeding on game fish and other bony fish, squid, other sharks. Arguably the fastest fish in the sea the mako shark can attain bursts of speed of up to 35 km/h and are often seen performing spectacular leaps from the water – this characteristic behavior is not fully understood. Shortfin makos respond well to bait and electrical impulses and will test divers in a baited environment. Dives with mako sharks are available from Cape Town. As with other offshore species like the blue shark, mako sharks are very susceptible to long-lining and their conservation status must be regarded as highly vulnerable.
BRONZE WHALER or COPPER SHARK – Carcharhinus brachyurus
Identification: Bronze whalers can attain a length of over 3m. The sleek body has a bronze-grey sheen dorsally with an off-white underside and is slightly arched above the gills. The fins are well developed and fin tips can be darker – especially on the lower caudal lobe and anal fin – causing much confusion with identification. The upper lobe of the caudal fin is more than double the size of the lower. Teeth on the upper jaw are pointed, triangular and slightly slanted. The teeth on the lower jaw are narrower, straighter and smoother. Seen underwater, bronze whalers are easily confused with blacktips (C. limbatus), however the pectoral fins are forward from the leading edge of the dorsal which is less prominent in bronze whalers.
Biology: Sexual maturity is reached after about 5 years. Young are born live in litters of up to 30 in number.
Behavior: Primarily found in shallow waters, the bronze whaler favours the cooler, temperate waters of the Cape and large numbers are known to follow the sardine run up the Wild Coast to KwaZulu Natal. Bronze whalers often feed near the bottom, their diet consisting of bony fish, small sharks, skates and squid.
DUSKY SHARK - Carcharhinus obscurus.
Identification: The absence of distinctive markings is, paradoxically, one of the best means of identification. Dusky sharks are grey to bronze in colour with a lighter underbelly. The snout is rounded . Fin tips are darker but not boldly marked. The tip of the dorsal is rounded and the pectoral fins are forward of the dorsal fin and black tipped on the underside. Teeth are triangular and serrated on the upper jaw. Teeth on the lower jaw are slender, smooth and more pointed. Dusky sharks have an interdorsal ridge and larger specimens may attain 4.2m in length.
Biology: The dusky shark bears up to 14 live young in the summer months.
Behavior: Dusky sharks are found in coastal waters from Cape Town to the tropics. Commonly caught by anglers and never implicated in attacks on humans, dusky sharks are however the most common catch of the shark nets in KwaZulu Natal. The proliferation of juvenile dusky sharks in the KZN area is prehaps due to the removal of many of the large predatory species by the very same nets. Dusky sharks feed on pelagic and bottom fish, other sharks, skates, rays and carrion - see report on scavenging behavior.
BLACKTIP SHARK - Carcharhinus limbatus.
Identification: Blacktip sharks are dark brown-bronze in colour with a lighter underbelly and a distinctive light band on the flanks. The body is stout, with a high dorsal fin and a pointed snout. Fin tips are usually black on pectorals, second dorsal, ventral caudal lobe, and the trailing edge of the first dorsal. The anal fin has no black tip unlike that of the spinner shark (Carcharhinus brevipinna) with which it is often misidentified. Teeth are narrow and cusped on the upper jaw. Blacktip sharks have no ridge between dorsal fins and can attain 2.6m in length.
Biology: Blacktip sharks may bear 1-10 pups (usually 4-7) born live in inshore nursery grounds after 10 to 12 month gestation in alternate years.
Behavior: Blacktips can be found in east coast estuaries and open ocean up as far as the tropics. Preferring to feed on large pelagic bony fish they are very active, fast swimmers, considered a pest by fishermen as they will readily steal fish off the line. Blacktips will also feed on smaller sharks, rays, cuttlefish, lobster and bottom fish. Blacktips seem to respond well to sound and divers may maintain shark interest with repetitive clicking sounds. Often found in larger groups they are easily attracted with fish chum and blood and are often a highlight on baited dives. More on baited shark dives…
SILVERTIP SHARK - Carcharhinus albimarginatus
Identification: Silvertip sharks are a strikingly beautiful shark, brown-bronze in colour with a lighter underbelly and a distinctive silver-white margins on the trailing edge of all fins. The body is stout, with a high dorsal fin and a narrow but rounded snout. Teeth are broad triangular and strongly serrated on the upper jaw. Teeth on the lower jaw are more slender, smoother and pointed. Silvertip sharks have a inter-dorsal ridge and can attain 3m in length.
Biology: Silvertip sharks may bear 1-11 live pups in the summer months, after a 10 to 12 month gestation period. Pups are between 60 and 70 cm in length at birth, living among shallow reefs and feeding on small fishes before venturing out into deeper water.
Behavior: Silvertips can be found on the east coast of Africa from Sodwana Bay to the Red Sea, on inshore edges and deep dropoffs around ocean sea mounts and islands in depths of upto 800m. Silvertips feed on both benthic and pelagic prey including tuna, smaller sharks, rays, squid and octopus. Most frequently sighted singly, silvertips tend to keep a distance from divers and swimmers, although will congregate in numbers and become excited and bold when bait is present – see dive report from Juan De Nova.
OTHER SHARKS OF SOUTH AFRICA: Sightings of large pelagic sharks in South Africa are mostly confined to recognised areas – either at breeding sites or where food is most abundant – see Protea Banks, Aliwal Shoal, Sodwana Bay and cage diving. Basking sharks, thresher sharks, cow sharks, white tip reef sharks, soupfin and numerous smaller reef sharks are amongst the many species found in our coastal waters and not as yet included in this text.
Copyright: Oceans Africa 2012 Original artwork: Graeme S. Grant