Bunaken Marine Park is world renowned for being one of the most diverse coral reef ecosystems in the world. For an ecosystem to be diverse, there must be a food chain, and naturally, there must be something that sits at the top of the food chain. This will usually be larger species of fish such as tuna, shark, or even orca (all of which can be found through the region, and have been spotted recently around Siladen).
In Bunaken Marine Park, the blacktip reef shark is one of the species that sits atop of the food chain, and it is something that all divers and snorkellers are more than happy to see.Â
What is a Blacktip Reef Shark?
Known scientifically as Carcharhinus melanopterus, the black tip reef shark is a small species of requiem shark â the same family that includes other well known sharks such as the tiger shark, bull shark, and white tip reef shark.
How to Identify a Blacktip Reef Shark?Â
As a species of requiem shark, blacktip reef sharks have a very typical âshark lookâ. They have a powerful looking broad body and a short rounded snout. They are most easily identified by their fins, which as their common name implies, are tipped with black. While all the fins are usually tipped with black, it is most noticeable on the first dorsal fin and the caudal fins.
Measuring an average of 1.6 metres and weighing up to 14 kilograms, blacktip reef sharks are among the smaller species of requiem sharks â they are relatively comparable in length to our other common shark sighting, the white tip reef shark.
What do Blacktip Reef Sharks Eat?
Like other requiem sharks, blacktip reef sharks are specialised hunters in open waters, and sit comfortably at the top of the food chain.
Using their strength, speed, and numbers, blacktip reef sharks can wreak havoc on small to medium sized reef fish â their primary target. They feed mainly of fish such as groupers, mullet, jacks, butterflyfish, parrotfish or wrasses, although they are also known to eat invertebrates such as octopus or cuttlefish.
Like all top predators, blacktip reef shark play a vital role in balancing the food chain and preventing any particular species from becoming too numerous. They have been observed travelling and working in groups to force fish into shallow waters where they can easily pick them out, and they are known (unlike whitetip reef sharks) to get stirred into a feeding frenzy if they can detect the scent of an injured fish in the water.
Blacktip Reef Shark Reproduction
Blacktip reef sharks are viviparous â which means the embryo develops inside the body of the mother, resulting in live birth after the gestation period is over.
The female blacktip will initiate the mating ritual by swimming close to the substrate with her head pointed down. Once the male blacktip finds her, he will swim very closely behind her, often bumping her or biting gently behind the gills. Once this âdanceâ has gone on for a while, the male will initiate the mating by pushing the female into the mating position. The actual mating can laster for several minutes, and once it is over, the two sharks will separate.
The gestation period is roughly ten months, although this can vary depending on the region. When the mother is ready to give birth, she will head into shallow waters for the safety of the pups. She will give birth to between two and five pups who measure between 35 and 50 centimetres each.
Juvenile blacktip reef sharks receive no form of parental care from either parent, and they will spend their first few years living in groups in extremely shallow water â often just deep enough to cover their bodies. They grow rapidly in the first couple of years (often more than 20cm a year) before slowing down to 5cm a year. Once they reach roughly one metre, they will reach sexual maturity and move into deeper water where they will begin looking for a mate of their own.
Where Can I Spot Blacktip Reef Sharks?
Although shark sightings are not as common throughout Bunaken as turtle sightings, we still have a number of dive sites where encounters are fairly common.
Most encounters are on deep walls or slopes in areas that are prone to currents. Probably our most successful shark spotting site is Sachiko â on the north east corner of Bunaken, and Tanjung Kopi â a thrilling coral encrusted slope on the north side of Manado Tua, although they can be found at almost any site within Bunaken Marine Park.
Generally blacktip reef sharks prefer to live in shallower waters, however they are known to live as deep as 75 metres. Around Bunaken Marine Park, adults sharks seem to come a little shallower in the early morning, and then again in the afternoon, spending the middle of the day at depths of 40 metres or deeper. The adult sharks are notoriously shy, and will often pass by several metres below you at quite a speed. Photographing them is extremely difficult, however if you have one circling below you for some time you can get nice video footage of them.
Possibly your best bet at finding blacktip reef sharks is while snorkelling. Because the juveniles spend their entire lives in very shallow water, you have a good chance of finding some by just walking off the beach at high tide. We have found the best spot for seeing them around Siladen is by walking towards the rocks at the end of the beach (right of the resort facing the sea) and snorkelling around the small rocks. Sometimes they can even be spotted while kayaking or stand up paddle boarding.