Everybody remembers their first shark sighting.
Mine was before I was a diver, while I was snorkeling on the Great Barrier Reef in Australia on a family holiday. It was dusk, and this large shadow rushes past me. I remember looking up and seeing this huge (or at least it seemed huge at the time), powerful looking fish swim only three or four metres from me. Excited and nervous, I headed back to shore soon after, but I remembered a few distinctive characteristics to help identify the species.
Speaking to another snorkeler on shore, I described the shark as having black markings on the fins, which they instantly identified as a blacktip reef shark – among the most common shark species in the area.
Now, after many years of diving and teaching, and many more shark sightings, I have had the pleasure of showing numerous students their first ever sharks, almost all of which have been blacktip reef sharks.
What is a Blacktip Reef Shark?
Scientifically known as Carcharhinus melanopterus, the blacktip reef shark is a small species of requiem shark – a family that includes other well known shark species such as tiger sharks, bull sharks, and lemon sharks.
What Does a Blacktip Reef Shark Look Like?
As a species of requiem shark, blacktip reef sharks look very much like your typical shark – streamlined, robust, and with short, rounded snouts.
As the name ‘black tip’ implies, all of the fins are tipped with black. This is always very obvious as the normal grey colour fades slightly before the black markings, making it stick out, and it is most obvious on the first dorsal fin.
Blacktip reef sharks are among the smaller of the requiem sharks, averaging at 1.6 metres in length (although there are rare cases of them reaching up to two metres) and weighing as much as 14 kilograms.
Blacktip Reef Shark Range
Found throughout most of the tropical and subtropical Indo-Pacific, blacktip reef sharks are among the most common sharks encountered by divers, and probably the most common among snorkelers.
They are common along the entire east coast of Africa -including Madagascar and the Red Sea – and can be seen throughout the Indian Ocean archipelagos such as the Maldives and the Seychelles. From here, they live along the entire southern Asian coastline, across the whole of South East Asia, and along much of the Chinese coast, the southern most of the Korean peninsula and southern Japan.
In Australia, they live along the north coast, and as far south as Brisbane on the east coast, and Perth on the west coast. They are also present throughout many of the Pacific archipelagos, including Hawaii.
There is also a small population of blacktip reef sharks living in the eastern Mediterranean, however they are not native to the region, having traveled up the Suez Canal from the Red Sea – a migration known as Lessepsian migration.
Blacktip Reef Shark Habitat
Like other reef sharks, blacktip reef sharks prefer to live in shallower waters, although they have been reported as deep as 75 metres.
When young, they prefer to live in very shallow water – often as little as two metres deep or shallower. Encounters with juveniles are common in areas with a large tidal excursion, as the sharks take the opportunity to swim far into the shallows for protection, although as the tide recedes they must head back into deeper waters so they don’t get stranded.
They have even been reported in brackish environments such as estuaries, and there are ever a few sightings in freshwater environments such as lakes and rivers. Although they can live in low salinity environments, they cannot tolerate it to the same extent of the Bull Shark, and must quickly move back into salt water.
Blacktip Reef Shark Feeding Habitat
Like all other requiem sharks, blacktip reef sharks are powerful and energetic hunters who are either at the top, or near the top of the food chain.
As they are often the most numerous apex predator in their environment, blacktip reef sharks play a vital role in balancing the food chain. They feed on many species of small to medium sized fish, including but not limited to; mullet, jacks, groupers, wrasses and surgeonfish. They have been observed working together to force schools of fish into shallower waters where they can be easily picked off.
Although their main prey tends to be small to medium sized fish, they will also eat invertebrates such as octopus, squid, cuttlefish, and shrimp if they get the chance, and although rare, they are known to eat rays and other, smaller sharks.
Blacktip reef sharks are easily attracted by splashing, sound (particularly metal on metal), and the scent of injured fish in the water. Once they begin to gather in larger numbers, they can become overly excited and even enter into a feeding frenzy – an ecological term for when too many predators gather together and start going crazy, trying to bite anything that moves. This this reason, it is not recommended to spearfish in areas that blacktip reef sharks are known to live.
Blacktip Reef Shark Life Cycle
Like most other sharks, blacktip reef sharks are viviparous, meaning the embryo develops inside the body of the parent, which leads to live birth after a gestation period.
The female blacktip will begin the mating ritual by swimming slowly near the sea bed with her head pointed down. Once the male finds her (there is substantial evidence that the female releases chemical signals into the water to attract a mate), he will swim very close to her, often bumping her or even biting her behind the gills. After swimming like this for a while, the male will push the female into a position where he can mate. The mating itself can last several minutes, and once complete, they will separate and continue as normal.
The gestation period is different depending on the region of the shark. In the Indian Ocean it is reported to last as long as 10-11 months, while off northern Australia it lasts between 7-9 months. Once the mother is ready to give birth, she will head into a shallow nursery area, and give birth to between two and five pups – averaging four – who measure between 35 and 50 centimetres each.
Upon birth, the juvenile blacktip reef sharks receive no parental care. They spend most of their first years in very shallow water (usually only just deep enough to cover their bodies), where they will hunt for small fish and invertebrates. Growth is rapid at first, with up to 23 centimetres a year for the first two years, and after that slowing to five centimetres a year. They reach sexual maturity when they reach roughly one metre in length, at which point they will head into deeper waters to hunt and mate.
How do Blacktip Reef Sharks Interact with Humans?
Blacktip reef sharks are a curious but timid species, and will often pass by divers and snorkellers (from a distance) a few times to check you out. They are attracted to sound, and many divers and dive operators use plastic bottles or metal banging to attract them. This behaviour should be discouraged, as if too many get attracted, they may be pushed into a feeding frenzy.
They are known to be aggressive when there is bait nearby, so spearfishing and pole fishing should be avoided in areas they are known to live. There have been very recorded incidents involving humans being bitten, and there have been no fatalities attributed to blacktip reef sharks. They are considered among the safest shark species to swim and dive with.
Where Can I Dive with Blacktip Reef Sharks?
As they are among the most common sharks within their range, there are countless opportunities to dive with these curious predators.
They tend to be quite territorial, so dive centres know where to find them if they are present in the area. They are extremely common throughout much of the Red Sea, Hawaii, Fiji, and throughout the Coral Triangle, especially Komodo, Indonesia.
For snorkeling, the best way to find them is by swimming close to mangrove areas, as the juveniles use the tangled roots as a safe haven from larger predators, and as many other small fish hide in the mangroves, there is ample food supply. The juveniles are common throughout their entire range in such habitats, as well as shallow sea grass areas and close to protected beaches.
Have you seen blacktip reef sharks before? Was it your first shark sighting too? We would love to hear about any encounters you have had with these beautiful and elegant creatures. If you have a story to share, please leave it in the comments box below and we will make sure to get back to you.
Photo credit: Kydd Pollock & MantaRay.com