Silky Shark - Carcharhinus falciformis

The Species

Silky sharks (Carcharhinus falciformis) are pelagic sharks found circumglobal in tropical waters, often near the edge of continental and insular shelves and slopes, and over deepwater reefs. With a maximum length of about 3.3 m, these sharks are among the larger species in the Red Sea. They are known for their inquisitiveness and curiosity towards boats and divers.

Lacking conspicuous fin markings this slender shark is best recognised by its rather small, triangular, round-tipped first dorsal fin, and the often metallic tinge to the overall grey-brownish coloration.

Not much is known about their movement patterns in the Red Sea. After being virtually non-existent at Egyptian dive sites since summer 2006, they made a spectacular return in 2010 appearing frequently at the offshore islands, in St. Johns and even close to the Sinai peninsula over the wreck of the Thistlegorm.

Globally, their open-ocean habitat makes them vulnerable to a wide variety of pelagic fisheries, most notably longlining and purse seining; they are taken in large numbers, with no available population estimates and most catches being unreported. Wherever analysed though, dramatic declines have been reported throughout their range.

One of the main concerns regarding silky sharks is their low reproductive potential; they reach sexual maturity at an age of 6-12 years, and give live-birth to a maximum of 6-15 pups every one or two years.

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

Suitable Markings

Individual markings on silky sharks are not as obvious as the colour markings found on e.g. oceanic whitetip or grey reef sharks. Identifying them is more challenging and might require higher quality photographs than for the other species, but it is possible especially looking at:

• shape and notch pattern on the first dorsal fin
• notch patterns on other fins
• grey-to-white line from the eye to the pectoral fin
• scars or irregular pigmentation patterns on various body parts

Some of these markings will need to be examined for stability over time, since the maximum period between different photographs of the same individual ia, at the moment only 3 months...

Individual catalogue

In a first attempt to create an individual silky shark catalogue, about 530 photographs and videos were analysed and 24 different sharks identified, the majority (12) from Brother Islands, another 8 from Daedalus. 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.