Blacktip Reef Sharks and the Similan Islands

The Blacktip Reef Shark is one of the more common sharks we see on our dives. While they have the outline of the typical sharks, they are often quite small – less than 1.5m. While many of the Sharks we have tend towards the deeper sites, this is one that can be seen be snorkelers. So this is a shark actually best seen from our Day Trips, rather than the Liveaboards.

Carcharhinus melanopterus
Blacktip Reef Shark
 

Description & Behavior
The blacktip reef shark, Carcharhinus melanopterus (Quoy and Gaimard, 1824), is a small shark measuring up to 1.8 m with a short, bluntly-rounded snout, oval eyes, and narrow-cusped teeth. There are 2 dorsal fins, no interdorsal ridge. Juveniles (<70>

World Range & Habitat
This species is commonly found in shallow waters on and near coral reefs and occasionally in brackish waters. Juveniles are typically found in extremely shallow water (±15 to 100 cm) inside lagoons, often swimming along the shoreline; adults typically occur on shallow parts of the forereef, often moving over the reef crest and onto the reef flat at flood tide. Individual adults inhabit a relatively small home range of ±2.5 km2 and appear to reside close to their home reef but occasionally cross deepwater channels between adjacent reefs.

They are also found in mangrove areas (our pier is located in a Mangrove swamp), moving in and out with the tide and even in fresh water near the sea. They occur singly or in small groups. Adults often aggregate in reef channels at low tide. This is one of the three most common reef sharks in the Indo-Pacific, the two others are the grey reef shark, Carcharhinus amblyrhynchos and whitetip reef shark, Triaenodon obesus.

They are found in the Indo-Pacific from the Red Sea and East Africa to the Hawaiian Islands and the Tuamotu Archipelago. They are also found in the eastern Mediterranean (through the Suez Canal).

Local Sites

These sharks are found on many of our local sites. They are also one of the few sharks that are frequently seen by snorkelers. They are a great way to deal with any shark fears that might happen. They look like the stereotypical shark, but are very small.

They are most frequently seen in the shallow reef flats that typify the Eastern Similans. The most frequent sightings are at Breakfast Bend, Beacon Reef, Anita’s Reef
 
Feeding Behavior (Ecology)
The blacktip reef shark is a fast, pursuit predator that prefers reef fishes, but also feeds on stingrays, crabs, mantis shrimps and other crustaceans, cephalopods, and other mollusks. In the Maldives, this species has been documented feeding cooperatively on small schooling fishes, herding them against the shore and feeding en masse. Feeds heavily on sea snakes in northern Australia. A large individual (1.6 m) was recently observed attacking a green sea turtle, Chelonia mydas, in North Male’ Atoll, Maldives.

Life History
Blacktip reef sharks are viviparous with a yolk-sac placenta, with a gestation period about 10 months and litter size of 2-4 pups. Size at birth ranges from 33-52 cm. Males mature at about eight years of age and 95-105 cm in length; females mature at about 9 years old and a length of 93-110 cm. Courtship features the one or more males following closely behind a female. Reproductive behavior includes distinct pairing with embrace where the male grasps the female’s pectoral fin between his teeth and mates belly to belly. There is one breeding season in the central and western Pacific, but two seasons in the Indian Ocean. Females rest for 8-14 month between pregnancies to rebuild their energy stores. Blacktip reef sharks are preyed upon by other sharks and large groupers. The is a socially complex species that performs a variety of group behaviors.

Comments
Blacktip reef sharks are regularly caught by inshore fisheries and are vulnerable to depletion because of their small litter sizes and long gestation periods. Traumatogenic. May become aggressive to spear fishers and are reported to bite people wading in shallow water. Generally marketed fresh (as fillet), may be dried, salted, smoked or frozen. Fins are valued for shark-fin soup; a market that is decimating shark populations worldwide. They are also sought for their liver as source of oil.

We have proven that the more Blacktips we have, the more income is generated for Snorkeling and diving. They are harmless (to humans) and the encounters are exciting and very memorable. In regions of the Caribbean it has been shown that each shark is worth Thousands of Euros to the tourist industry, and continues to generate this income over the course of it’s lifetime. Whereas the harvested shark is a onetime source of income.

They UN listed them as “near Threatened”


Wikipedia is a great source of information with some really nice links as well for follow up research. We Used them, Elasmo-divers and several books, but primarily “Sharks and Rays of the World” by Debelius.

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