Feature Creature

GREY REEF SHARK CARCHARHINUS AMBLYRHYNCHOS

FEATURE IUCN RED LIST 2009

PHOTOGRAPHY SIMONE CAPRODOSSI

RED LIST CATEGORY & CRITERIA: NEAR THREATENED

Scientific Name: Carcharhinus amblyrhynchos

Synonym(s): Carcharhinus wheeleri Garrick, 1982 Carcharias nesiotes Snyder, 1904 Carcharias amblyrhynchos Bleeker, 1856 Galeolamna coongoola Whitley, 1964 Galeolamna fowleri Whitley, 1944 Galeolamna tufiensis Whitley, 1949

Authority: (Bleeker, 1856)

Common Names: Grey Reef Shark, Gray Reef Shark

JUSTIFICATION This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).

The Grey Reef Shark (Carcharhinus amblyrhynchos) is a widespread, social species that formerly was common in clear, tropical, coastal waters and oceanic atolls. Its restricted habitat, site fidelity, inshore distribution, small litter size, and relatively late age at maturity, along with increasing fishing pressure suggests that this species may be under threat. Although caught in tropical multispecies fisheries, it has considerably greater value in dive tourism if protected. With time and additional data, this Near Threatened assessment may need to be revised.

GEOGRAPHIC RANGE NATIVE: Extant (resident) Australia; British Indian Ocean Territory (Chagos Archipelago); French Polynesia (Tuamotu); Indonesia; Madagascar; Réunion; Seychelles; United States (Hawaiian Is.)

The Grey Reef Shark is a widespread species occurring in the central Pacific and westwards to the eastern Indian Ocean. Garrick (1982) notes his most eastern records of this species from Tuamoto Archipelago in the south and the Hawaiian Islands in the north, west through the Pacific, northern coast of Australia, Indonesia, Sumatra and west to Madagascar in the Indian Ocean, including the Seychelles and Reunion (see Compagno 1984 and Last and Stevens 1994 for maps).

POPULATION This shark has been recorded as locally highly abundant at some sites. Some local populations have been severely depleted.

HABITAT AND ECOLOGY The species is found in clear tropical waters often from 10 m to more than 50 m around coral reefs, particularly near drop-offs and passes of fringing reefs. It is more common at ancient atolls, and less common at high profile islands with extensive human habitation, or in turbid continental waters (Randall 1986, Wetherbee et al. 1997). At unexploited sites Grey Reef Sharks are one of the most common tropical reef sharks that may be found in groups or individually. Potentially dangerous when harassed, they have been shown to display stereotypical threats (Johnson and Nelson 1973, Nelson 1981, Randall 1986). Divers are advised to keep their distance and not take strobe photographs when sharks display erratic swimming.

Males mature at 120-140 cm total length (TL) and attain a size of 185 cm; females mature at about 125 cm TL and attain 190 cm (Wetherbee et al. 1997) at about seven years. Litters are small, up to six embryos (Compagno 1984b, Last and Stevens 1994, Wetherbee et al. 1997). Seasonality is uncertain because of limited data. Parturition may be in August with a nine month gestation possible in the southern hemisphere (Stevens and McLoughlin 1991). Mating and fertilisation take place in March-May (or July). Pupping appears to occur from March to July off Hawaii, suggesting a 12 month gestation, but females reproduce every other year (Wetherbee et al. 1997). Fish form the bulk of the prey while squids, octopuses and crustaceans are less important food items (Salini et al. 1992, Wetherbee et al. 1997).

THREATS This shark shows high site fidelity and some local populations have been severely depleted by modest fishing pressure, as has been shown off Hawaii (Wetherbee et al. 1997). Very marked declines of sharks, including Grey Reef Sharks, have been reported in the Chagos Archipelago (Indian Ocean) between the 1970s and 1996. Shark numbers here were reduced to only 14% of the numbers found in the 1970s (Anderson et al. 1998). The quality of its coral reef habitat is threatened in many parts of the world.

CONSERVATION ACTIONS Smith et al. (1998) found this species to have moderate rebound potential, so it should respond positively to effective management measures. Because Grey Reef Sharks are found in clear tropical waters over coral reefs, they are ideal for non-consumptive (but much more lucrative) use in the form of tourism diving, as has been shown by Anderson and Ahmed (1993). For this reason, shark populations at some of the most important reef diving sites in the Maldives are now protected.

CITATION Smale, M.J. 2009. Carcharhinus amblyrhynchos. The IUCN Red List of Threatened Species 2009. www.iucnredlist.org