How Sharks' dorsal fin can be used like fingerprints on humans to study their population...
To study a wild population of animals it is necessary to be able to identify and recognize the individuals in that population. Up until recently, most ecologists used artificial tags in wildlife studies to identify the individual animals. But these tags can easily be lost or be overgrown with parasites and algae especially in the marine environment. In 1997, Michael Scholl developed an innovative photographic based identification technique using the individual notches and markings naturally present on the dorsal fin of White Sharks: finprinting. This method was based on the ones used by many Cetacean scientists to identify Dolphins and Whales, but it had never been implemented before with Elasmobranchs as the main identification technique. Photographic identification presents several advantages over artificial tags:
- it is non-invasive unlike standard tagging with streamer or plaque tags;
- free-swimming Sharks can be identified from a greater distance than from artificial tags; and
- photographs of dorsal fins could be collected by the cage dive operators and tourists, which they can submit to the catalogue, creating further public awareness and support for White Shark conservation.
Since then, the photographic identification technique has be adapted to other Elasmobranch species: Basking, Whale, Tiger and Ragged Tooth Sharks.
Michael Scholl founded a non-profit organisation, the White Shark Trust, that was established to locate and manage funding, and lead research, conservation and education projects. Using the finprinting methodology, Michael initiated and lead a permanent in-depth research project on the ecology of the White Shark population from 1997 to 2007 during which over 8’000 shark observations were recorded with detailed information and photographs, during nearly 1’800 days spent at sea in the area around Dyer Island mainly. The resulting White Shark Trust database is to date the most detailed and extensive population database on White Sharks in the world with over 1’500 different White Sharks identified.
Michael Scholl has shown that over 80% of White Sharks could be positively identified using their dorsal fins alone and that this method could be used to identify White Sharks over a long period: some Sharks have an observation history of over 2’000 days. The project has so far identified that certain sharks return on a regular basis to the Dyer Island area (see Nicole’s section). The project has also provided Marine and Coastal Management with sufficient data and results to extend the commercial white shark diving allowed area to include a secondary location, known as Shark Bay, as the sharks seem to use the area differently throughout the year. This project has developed tools allowing the broader study of the dynamics and structure of White Shark population(s) worldwide. The White Shark is an endangered animal, and in order to adequately protect this species and extend its conservation status globally, more information is needed about their ecology and biology. One of the problems with White Shark protection and conservation legislation is the lack of this basic information – reliable population estimate, mating grounds, nursery grounds, age at maturity, migration routes and trends, etc. The problematic of showing that the population of White Sharks has decreased significantly is difficult considering that no reliable population estimate exist to date and no information about the original population size is available. Even the national protection status that White Sharks gained in South Africa in April 1991 was based on the precautionary principle. This project will give scientists and legislators the best population estimates to date.
In the future, Michael Scholl is working on publishing the White Shark Trust population database on the internet to be accessible for scientists around the world and to allow for the database to live on and grow with White Shark sightings from around the world: sharkphotoid.com. However, funding is needed to see this database live and accessible on the internet. Michael Scholl is also investigating the development of a dedicated software for the necessary automatic identification of dorsal fin photographs.