Grey Reef Shark
Carcharhinus amblyrhynchosThis somewhat stout shark has the classic dark upper and white lower coloring, but has a distinct dark margin on the caudal fin (tail) and often a pale or white-edged dorsal fin (unlike the blacktip reef shark which has a black tipped dorsal fin). These social sharks gather in groups during the day and hunt alone at night, and because of their social nature, they show curiosity to divers. Although they are strong and aggressive, they are not likely to attack humans unless threatened or alone.
English language common names include grey reef shark, blacktail reef shark, black-vee whaler, bronze whaler, gray reef shark, gray shark, gray whaler shark, longnose blacktail shark, shark, and whaler shark. Other common names from across the world include 'anga (Tongan), bagea totoho (Gela), grijze rifhaai (Dutch), grys rifhaai (Afrikaans), ikan yu (Malay), jarjur (Arabic), kortneus-swartsterthaai (Afrikaans), mago (Niuean), malie-aloalo (Samoan), marracho enlutado (Portuguese), nga-man-nee (Burmese), pako mej (Marshallese), pating (Tagalog), qio dravu (Fijian), raira (Tahitian), requin à queue noire (French), requin bar (French), requin blanc (French), requin dagsit (French), requin gris (French), te alava (Tuvaluan), te bakoanimarawa (Kiribati), tiburón coralero rabinegro (Spanish), and tiburón de arrecifes (Spanish).
Importance to HumansThe grey reef shark may be taken by longline shark fisheries and are valued for their fins that are used in shark fin soup. It is also utilized for human consumption and fishmeal. However, this species often occurs out of the range of most commercial shark fisheries.
Danger to Humans
Although it is one of the most aggressive sharks, the grey reef shark will usually only attack a person when it is threatened. Even so, it has been responsible for 7 unprovoked attacks resulting in no fatalities according to the International Shark Attack File. This shark often shows curiosity and often approaches divers. If cornered or threatened is some way, the grey reef shark will display threat behavior explicitly. It will raise its snout, depress the pectoral fins, and arch its back while swimming with an exaggerated sway. If the threat continues, the shark will move with lightening speed, delivering quite bites prior to retreating. Although the bites are often serious, they are rarely fatal. This species of shark is also more likely to attack while solitary rather than schooling perhaps due to an increased feeling of vulnerability.
The grey reef shark is vulnerable to overfishing due to its restricted habitat, small litter size, and relatively late age of maturity. These factors, along with an increase in unmanaged fishing pressure, make this shark vulnerable to threats. However, at this time there is not enough data on the grey reef shark to analyze the status of populations.
The grey reef shark is currently listed by the World Conservation Union (IUCN) as "Near Threatened". More fisheries data is required for future assessment. The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.
Geographical DistributionThe grey reef shark is limited to the Pacific and Indian Oceans. In the Indo-Pacific, it is found in the waters off Madagascar and in the Mauritius-Seychelles region. In the western Pacific Ocean, this shark ranges from southern China to northern Australia and the Tuamoto Archipelago. It is one of the most common reef sharks in the Pacific Ocean, along with the blacktip reef shark (Carcharhinus melanopterus) and the whitetip reef shark (Triaenodon obesus). It is also found in the Indian Ocean, off the coast of India to South Africa, including the Red Sea. In this region it is often referred to as Carcharhinus wheeleri.
Primarily distributed in shallow tropical and subtropical waters, the grey reef shark is often found near coral atolls and lagoons adjacent to reef habitats. It is often observed swimming along the outer edges of coral reefs. Its depth ranges from 0-920 feet (0-280 m). However, this species has been observed in waters down to 3,280 feet (1,000 m). Although more active during the night, grey reef sharks sometimes form schools during the day. These schools swim close to the bottom, over flat habitats. Grey reef sharks also form loose aggregations that lurk close to reef drop-offs. Lone individuals may be seen over shallow reefs either lying motionless on the bottom of the sea floor for long periods of time or swimming. Tagging studies show that sharks living near ocean reefs are nomadic and travel long distances along the reef habitat each day. Sharks residing in lagoon areas tend to return day after day to the same site.
This shark is medium to large in size, growing up to 8.4 feet (2.6 m) in length. It has a long, broadly rounded snout and large eyes. It does not have an interdorsal ridge running between the first and second dorsal fins. The origin of the first dorsal fin is over or just in front of the free rear tips of the pectoral fins. The first dorsal fin is semifalcate with a narrowly rounded or pointed tip. The second dorsal fin originates over the anal fin origin. The pectoral fins are large, narrow, and falcate in shape with narrowly rounded or pointed tips. Coloration
The dorsal side of the grey reef shark ranges from dark gray to bronze gray, paling to a white ventral side. The entire trailing edge of the caudal fin has a distinct wide black margin. The pectorals, second dorsal, anal, and pelvic fins have black or dusky tips while the first dorsal fin is either entirely gray or irregularly edged with white.
The grey reef shark may be confused with the blacktip reef shark (C. melanopterus). The blacktip reef shark can be distinguished by the distinct black tip on the first dorsal fin as well as black tips on the remaining fins.
The teeth are triangular and serrated with 13-14 teeth in each jaw half. The upper teeth are narrow and serrated, semi-erect to oblique in shape with high cusps. The crown feet have coarse serrations. The lower teeth are erect or semi-oblique with narrowly serrated cusps.
The grey reef shark may grow to a maximum size of 8.4 feet (2.6 m) in length and to weights of up to 74.3 pounds (33.7 kg). However, the average size of a grey reef shark is less than 6.6 feet (2 m) in length. The maximum reported age of this shark is about 25 years. Males mature at lengths of 4.3-4.9 feet (1.3-1.5 m) and females mature at 3.9-4.6 feet (1.2-1.4 m) in length, both corresponding to an age of approximately 7 years.
Reef fishes, along with smaller quantities of cephalopods (squid and octopus), and crustaceans (shrimp and lobster), provide the majority of the grey reef sharks' prey. Reef shark prey also includes bony fish including cowfish, surgeonfish, and butterflyfish. The grey reef shark will also prey on young individuals of their own species. Most of the feeding activity occurs during the nighttime hours which is also this shark's peak activity period.
The grey reef shark is a viviparous species, which refers to reproduction when the embryos are nourished with a yolksac placenta during gestation inside the mother. The gestation period lasts approximately 12 months, followed by live birth of a litter of 1-6 pups. Each pup measures between 15.7-23.6 inches (45-60 cm) in length at time of birth.
Predators of the grey reef shark include larger sharks such as the silvertip shark (Carcharhinus albimarginatus).
The grey reef shark is host to parasitic copepods including Nemesis robusta (gill filaments) and Alebion carchariae (snout, fins, body). These copepods were documented on specimens from waters off western Australia. Ganthiid isopod larvae have also been reported on the gills of this shark.
The grey reef shark was originally described as Carcharias amblyrhynchos by Bleeker in 1856. He later changed this name to the currently valid name of Carcharhinus amblyrhynchos. The genus name Carcharhinus is derived from the Greek "karcharos" meaning sharpen and "rhinos" meaning nose. Synonyms used in previous scientific literature that refer to the grey reef shark include Carcharias nesiotes Snyder 1904, Carcharhinus menisorrah Whitley 1944, Galeolamna fowleri Whitely 1944, Galeolamna turfiensis Whitely 1949, Galeolamna coongoola Whitely 1964, and Carcharhinus wheeleri Garrick 1982.
Prepared by: Cathleen Bester