Grey Reef Shark - Carcharhinus amblyrhynchos

The Species

Grey reef sharks are rather stocky sharks with a maximum length of about 2 m. They are easily recognised by the conspicuous black band all along the trailing edge of the tail. In the Red Sea, most of them also have a white tip or margin on the triangular first dorsal fin.

They are widespread throughout the tropical Indo-Pacific, including the Red Sea. Because of their association with coral reefs, especially reef walls and drop-offs, they are commonly encountered by divers throughout their range. Because of their high site fidelity at certain sites, even modest fishing pressure has seriously depleted local populations; others are suffering because of the degradation of their coral reef habitats.

Once depleted, grey reef shark populations are slow to recover; they reach sexual maturity at about seven years of age, and give live-birth to a maximum of 6 pups every other year.

Their worldwide status is given as 'near threatened' while population trend is 'unknown'.

Suitable Markings

Looking through photographs from the last 4 years, a variety of natural markings appear suitable for photo-identification purposes:

• the white tip/margin on the first dorsal fin
• shape of the black/grey border along the tail
• grey-to-white line from the eye to the pectoral fin
• shape of white colour band on the flanks
• irregular pigmentation patterns on various body parts

Photographs of the female shown above across almost 3 years show that these markings are stable enough to be used in this non-invasive technique.

Individual catalogue

In a first attempt to create an individual grey reef shark catalogue, about 110 photographs and videos, taken between April 2007 and May 2010, were analysed and 22 different sharks identified, the majority (15) from Brother Islands, another 5 from St Johns. See sidebar for examples.

Collection of additional images, from the present as well as past years, will help to increase our knowledge of this species' ecology and behaviour.