Photo-ID

Shark photo-identification has already been used in many species, mainly large-bodied ones, such as Carcharodon carcharias and Rhincodon typus, using natural variations in colour patterns on the body. It has also been used on the blacktip reef shark Carcharhinus melanopterus to look at the specific shape of margins separating black, white and brown colour patterns on the dorsal fin. The succession of coloured lines was shown to vary consistently and to be unique to each individual. Usually, we use photo-identification of both sides of the dorsal fin as well as other distinctive marks such as scars, notches and dots throughout the shark’s body.

Photoidentification of blacktip reef sharks. (a, b) Global view of both sides of (a) a female ‘Op19’ and (b) a male ‘V19M’; note the elongated claspers that extend beyond the pelvic fins in males (b) and their absence in females (a). (ceh) Photographs of both sides of the dorsal fin of six individual C. melanopterus: (c) ‘V12M’; (d) ‘Tao25’; (e) ‘Op26’; (f) ‘Op18’; (g) ‘Op27’ and (h) ‘V21M’ taken between 2008 and 2010; note the margin patterns between the black and white parts of the dorsal fin, which are unique to each individual. (i, j) Persistence of patterns over 10 years for (i) ‘V27F’ and (j) ‘V12F’. Photos: (aeh) Johann Mourier; (i, j top) Ila Porcher. (from Mourier et al. 2012)

For other species it is less obvious as their body colour is homogeneous and uniform. It is the case for example of bull sharks, grey reef sharks or lemon sharks. However, it is still possible to identify individuals from these species but it requires more work and a certain assiduity in the monitoring to identify the appearance and disappearance of patterns.

Sharks have incredible healing abilities (Chin et al. 2015) so it is important to monitor the looking of individuals continuously. Above, progressive and rapid healing of a 20 cm vertical cut on the second dorsal fin of a sicklefin lemon shark in Moorea from October 2004 to October 2005.