The Whitetip Reef Shark

  Predominantly inhabiting the Indian and Pacific Oceans, especially the Great Barrier Reef, where it is one of the most common sharks, whitetip reef sharks could be referred to as the wolves of the sea - dominating the ocean at night and swarming across reefs in their hundreds.

  Small and slow, whitetip reef sharks make for good aquarium exhibits and are a great attraction for divers in the wild. Although they are generally passive, these reef sharks have been known to attack spear-fishermen whilst trying to steal their catch. Numerous divers have been injured in the feeding frenzies that ensue, although these well-publicised events are few and far between.

  Dwelling in caves for the most part of the time, whitetips come to life at night as they prowl their reef-homes in the dark - preying on any unfortunate fish or crustacean they come across. With slender, cartilaginous bodies, they can easily press themselves into crevices or caves in search of food. Scavengers by nature, some whitetip reef sharks - most notably those of Hawaii - have learned to follow seals in order to steal their hard-earned meals. Others have developed the bait of waiting by reef drop-offs and catching the remains of fish,

Whitetip reef sharks rarely grow
to two metres in length.

which float in with the tide.

  A typical behaviour of reef sharks, whitetips often frequent cleaning stations on their reef, where cleaner wrasse and small fish feed on the many parasites sharks are known to suffer from. Copepods often attach themselves to whitetips in order to feed on their flesh.

  Their are, however, some more fearsome predators to the whitetip reef shark. Around America and Mexico, tiger sharks frequently kill whitetips for their meat, while silvertip sharks in Australia will attack any creature in order to defend their territory. Astonishingly, the remains of full grown whitetip reef sharks have been discovered in the stomachs of giant groupers. These gargantuan fish often inhabit the wreckages of boats and aeroplanes near to reefs and are easily capable of swallowing a shark whole. Due to their rarity, however, such an occurrence is not common and has only been witnessed a few times.

  Rarely leaving the reef they were born at, whitetip reef sharks have come to symbolise fidelity to the natives of many Pacific islands. This is generally attributed to their fear of the predators around their reefs, rather than to the sharks being instinctively territorial, as they are social creatures and often rest in large groups during the day.

  Sadly, whitetip numbers have declined in recent years due to the numerous fisheries hunting them for the hide, meat and liver oil. The destruction of their restricted reef-habitat has also played a large role in this, reducing their numbers abhorrently. Slow reproducers, it is quite possible that whitetips will be hunted to extinction in certain areas before they are able to repopulate.

A juvenile whitetip reef shark on the Great Barrier Reef. Note the distinctive
white fin and tail tips.

The Sicklefin Lemon Shark

The sicklefin lemon shark is rather rarer than the managrove-inhabiting lemon shark, commonly found in North America. Unlike its American counterpart, the sicklefin is most commonly found in Australia and East Africa. It inhabits lagoons and estuaries, where it can grow without fear of larger reef sharks like blacktips, silvertips and blacktip reef sharks.

Sicklefin lemon sharks feed on triggerfish, parrotfish and crustaceans, while older individuals have been known to prey on  rays, skates and guitarfish. Remains of sicklefins have been found in the stomachs of silvertip sharks, who are extremely territorial and will fight to the death if another shark enters their area of a reef. Often, they will indulge in a meal of over-curious shark in celebration.

Sicklefins grow up to 3.8 metres long and share the same build as lemon sharks (see above). They also share the same brown and yellow colouration. The main difference is, as the name suggests, the shape of the sicklefin's dorsal fin. It curves back in a sickle-like shape whereas that of the lemon shark does not.

The range of a sicklefin lemon shark.

A sicklefin lemon shark at a reef in the Pacific.

A lemon shark off the shore of Florida. Note the fin shape.

Note the differences between the fin shape of this sicklefin
lemon shark and the lemon shark (above left).

Silvertip Shark

  The silvertip shark is a magestic and sometimes scary member of the shark family. Commonly found in Northern Australia, Eastern Africa and Madagascar, the Carribean and Central American coasts, Saudi Arabia and China, it can be very territoreial and will fight to the death to keep other sharks and large, imposing sea creatures away from its territory. When it comes to hunting, however, the silvertip will not eat fish that are in its territory, but will venture from the coral reefs where they live into the open ocean which supplies them with larger, more substantial food. Silvertips are opertunistic and will take fish from fishing lines or drag them out of deep sea trawler nets by their tails.
  Although fatal shark attacks are rare, a silvertip mother will attack a human visciously if she feels they are threatening her litter, which will stay in their mother's territory until they are half-a-year old, or herself. If a human approaches a lone silvertip too quickly, the shark will become stressed and may attack. As of 2008, four provoked, and none unprovoked, silvertip attacks on humans have been confirmed-none of which were fatal-each was registered by the International Shark Attack File.
  A silvertip shark can be recognised by its distinctive silver dorsal fin tip. It is important for divers to register this when diving near one of these sharks-all but one of the attacks mentioned above were caused by the diver approaching a small silvertip under the impression it was a sluggish, harmless whitetip reef shark- the tail tips also have the silver markings.

A silvertip shark, warily guarding its territory from
competitors.