Ocean News

SOSSC Sevengill Shark Photo-ID – New Project

6th April 2009

We have initiated a new research project focused on a population of sevengill sharks (Notorynchus cepedianus) in False Bay, South Africa. We are evaluating the population structure of these sharks in an aggregation site and documenting social behaviour using underwater observations documented by video and photography. This project forms part of a larger collaborative study in development with the South African Shark Conservancy.

Effective approaches for the management and conservation of wildlife populations require a sound knowledge of population demographics. Traditionally collecting this information was often only possible through mark-recapture studies using invasive methods of marking individuals e.g. tagging or maiming. However, photo-identification (photo-ID) has become a widely accepted non-invasive method of mark-recapture that has been empirically tested over a broad range of species e.g. amphibians, reptiles, elasmobranches, birds and mammals. Photo-ID has successfully being used on a number of elasmobranchs including: the raggedtooth shark (Carcharias taurus), whale shark (Rhincodon typus), white shark (Carcharodon carcharias) and Manta ray (Manta birostris).

Sevengill sharks, as they are commonly called, are large top predators in coastal waters. They are identified by having a single dorsal fin, seven gill slits and broad, blunt heads. Their brown/grey bodies are covered in black and white spots. This spot pattern on their dorsal surface makes them potential candidates for photo-ID using freely available computer software.

To kick start this project Robert Raw, an Honours student from the University of Cape Town is assessing the viability of using photo-ID for these animals. The program requires a large database of photos and we are requesting divers who see these sharks and have cameras to take photographs of the dorsal surface as seen from directly above the shark for identification purposes. Robert has also requested local dive shops and underwater clubs to display our informational poster requesting diver participation and so far has got a lot of positive feedback.

All contributions will be greatly appreciated and acknowledged!
Honours student: Robert Raw – University of Cape Town
Supervisors of photo-ID project: Alison Kock – Save Our Seas Shark Centre & Dr. Andrea Marshall – Manta Ray & Whale Shark Research Centre, Mozambique

For a rare opportunity to dive with these incredible, ancient looking sharks in Cape Town, South Africa please contact Morne’ at sharkxplorer@gmail.com for more information.