Shark Diving Unlimited is very pleased that the latest scientific paper we sponsored for Dr Sara Andreotti of Stellenbosch University, has been published.

The lack of a standardized procedure for collecting data about elusive and hard to find species like the great white shark has to date seriously hampered efforts to manage and protect these animals.

But now a marine biologist, an applied mathematician and a software developer from Stellenbosch University joined expertise to develop a custom-made software package, called Identifin, which may offer a solution to this problem.

Dr Sara Andreotti, a marine biologist in the Department of Botany and Zoology at SU, have collected over 5000 photographic images of the dorsal fins of white sharks along the South African coastline as part of her research. This is because the trailing edge of the dorsal fin provides a unique trade, analogous to a human fingerprint.

Over six years she managed to manually build a database with information on when and where an individual white shark was sighted. In those cases where she was able to collect a biopsy from the shark, the genetic information was linked to its profile.

But she was doing all this manually on her personal computer.

“I nearly lost my head. I quickly realised that in the long term updating the database was going to consume more and more of my time. That is when I headed over campus to the applied mathematics division and asked for help. I was stunned when they became all excited about my data,” she laughs.

Prof. Ben Herbst, a specialist in machine learning, and Dr Pieter Holtzhausen, a software engineer then busy with his PhD in Applied Mathematics, were literally overjoyed to be able to work with Dr Andreotti’ s data base.

Dr Holtzhausen explains: “We used an algorithmic technique called dynamic time-warping to match the fingerprints. With this technique, any data that can be turned into a linear sequence can be analysed. The technique is often used in speech recognition software.”

The image recognition software they developed, called Identifin, compares a semi-automatically drawn trace of the back edge of the dorsal fin to existing images in the database. The images in the database are then re-arranged and ranked by probability of match. If there is a match, the database photograph in the first position will be the correct one.

This is what the interface of the Identifin - fin matching - program looks like. A researcher takes the original photograph (a) and indicates the top and the bottom of the fin. The software then automatically traces the notches pattern (in red). Image: courtesy Dr Sara Andreotti.

The researcher then asks the software to match the traced photograph with existing images from the sharks’ database. Image: Sara Andreotti

However, while working with Michael Meyer, a marine scientist from the Department of Environmental Affairs, and shark conservationist Michael Rutzen from Shark Diving Unlimited, Dr Andreotti realised that the software needed some more tweaking if it were to fit the ideal of sustaining a large database for the long-term monitoring of the white shark population.

“The software had to be capable of quickly matching the fin identification of a newly photographed shark with a possible existing match in the database, and to automatically update the sharks’ id catalogue. The database also had to be user-friendly and structured in such a way so that different researchers can use it over the long term,” she explains.

The custom-made software uses the complete database for comparing the matches and then organises them in order of similarity, from left to right. There is also an embedded function in the software to create a matrix of the history of recaptures. This information can be used to estimate population numbers. Image: Sara Andreotti

While there is still room for improvement, the success of the first trials boosted their hope that in the near future they will be able to use Identifin to monitor white shark populations on a large scale.

“Previously, while at sea, I had to try and memorize which shark is which, to prevent sampling the same individual more than once. Now Identifin can take over. I will only need to download the new photographic identifications from my camera onto a small field laptop and run the software to see if the sharks currently around the boat have been sampled or not.

“By knowing which sharks had not been sampled before we can focus the biopsy collections on them. This saves us both time and money when it comes to genetic analysis in the laboratory,” she adds.

Dr Andreotti says to date the lack of standardization of data collection has been a major limitation to combining datasets of worldwide distributed species: “We hope Identifin will offer a solution for the development of a South African and then global adaptive management plan for great white sharks.”

The next step is to adapt Identifin for the identification of other large marine species and help other researchers facing the same kind of struggles.

• The research was made possible with funding from Shark Diving Unlimited, the University of Stellenbosch, White Shark Diving Company and the Explorers Club.
• The research article, ‘Semi-automated software for dorsal fin photographic identification of marine species: application to Carcharodon carcharias’ was published in the journal Marine Biodiversity.
• A YouTube video with interviews and an animation of the technique available online at https://www.youtube.com/watch?v=2JNMnjVcXaI&feature=youtu.be

Contact details

Dr Sara Andreotti

E-mail: andreottisara@gmail.com

Mobile: 072 3219198

Dr Pieter Holtzhausen

E-mail: holtzhau@gmail.com

Mobile: 084 998 6386

Additional reading

Andreotti S, Rutzen M, Wesche PS, O’Connell CP, Meÿer M, Oosthuizen WH, Matthee CA (2014) A novel categorisation system to organize a large photo identification database for white sharks Carcharodon carcharias. African Journal of Marine Science 36:59–67. Available online at
http://www.tandfonline.com/doi/abs/10.2989/1814232X.2014.892027?journalCode=tams20

Andreotti S, Heyden S von der, Henriques R, Rutzen M, Meÿer M, Oosthuizen H, Matthee CA (2016) New insights into the evolutionary history of white sharks,Carcharodon carcharias. Journal of Biogeography 43:328–339. Available online at http://onlinelibrary.wiley.com/doi/10.1111/jbi.12641/abstract

Andreotti S, Rutzen M, Walt S van der, Heyden S Von der, Henriques R, Meÿer M, Oosthuizen H, Matthee C (2016) An integrated mark-recapture and genetic approach to estimate the population size of white sharks in South Africa. Marine Ecology Progress Series 552:241–253. Available online at http://www.int-res.com/abstracts/meps/v552/p241-253/

Issued by Wiida Fourie-Basson, Media: Faculty of Science, Stellenbosch University, 021 808-2684, science@sun.ac.za

There’s no greater sight than a 1 tonne Great White Shark launching itself out of the water, right by your boat, in hungry pursuit of a seal. Shark Diving Unlimited in Gansbaai, South Africa runs breaching trips from May to August each year so that you can witness this spectaculr behaviour.

Breaching is thought to be part of the Great White Shark’s hunting behaviour and only occurs in the South African winter months. It is thought that they only exhibit this activity in one place in the world, Gansbaai, two hours South of Cape Town. During winter visibility is excellent in this region and tours are especially popular with photographers and those who want to enjoy the majesty of these animals but don’t want to get their feet wet.

Breaching trips head out at first light and last approximately 2-3 hours. An artificial seal is towed behind the boat to entice this apex predator to breach and guests then brace themselves for this rare spectacle with cameras at the ready. During their visit guests are treated to breakfast, snacks on board and a light lunch after the trip.

Mike Rutzen, well known shark behaviourist, conservationist and owner of Shark Diving Unlimited, was the first person in the world to witness this behaviour from both above and below the water in his documentary Great White Shark: A Living Legend.

“The first time I saw this behaviour my heart skipped a beat, it is truly magnificent and right up there with observing lions hunting or fighting. The great white shark is worth a lot when slaughtered for its jaws and teeth, but alive it is truly the greatest sight”

Great White Sharks are listed as Vulnerable by the IUCN Red List and are primarily being threatened by baited hooks, which are used by the government to protect swimming beaches, by hooking (and in most cases killing) sharks. Poaching for the shark’s valuable jaws and teeth is also a huge problem in the preservation of this species.

Shark Diving Unlimited uses most of its profits to fund scientific research, in collaboration with Dr. Sara Andreotti, a marine biologist at Stellenbosch University. Together, they have been attempting to preserve the great white shark through a series of studies on their behaviour and genetics.

Shark Breaching trips are 10 000 ZAR per boat ride for 1-8 people and the cost is split between all the guests on any given trip. It is also possible to book an exclusive breaching trip for 10 000 ZAR. In addition, those wishing to go shark cage diving can do so all year round at a cost of 1500 ZAR. Return transfers from Cape Town are 450 ZAR per person return.

To book please email us at info@sharkdivingunlimited.com or call us all hours: +27 (0) 82 441 4555

Shark fin soup is a delicacy that tens of millions of sharks have been killed for. Here are a few facts about shark fin soup that will hopefully prompt you to support the banning of shark finning.

Why are sharks killed for their fins?

Sharks are caught and their fins are hacked off for the Asian delicacy, shark fin soup. Their fins are used to make a gelatinous soup that is tasteless and contains no nutritional value. Shark fin soup is also highly expensive; one shark fin can cost up to $400. Shark meat itself is of low value therefore shark finning is done on the boat after which the sharks are thrown overboard where they die from suffocation, drown or are eaten by other fish.

Why should people care?

Shark finning has killed tens of millions of sharks to date. At this moment, every species of shark is endangered. The systematic destruction of the species has serious consequences for ocean’s eco-system. Sharks are necessary apex predators who have been around for 300 million years. They regulate the population of other species of fish and mammals by eating them as prey.

What can you do?

• Support organisations that work to preserve sharks such as Shark Diving Unlimited
• Sign petitions and support legislation that work to ban shark finning
• Refuse to eat in restaurants that serve shark fin soup or shop where shark fins or shark products are sold
• Spread the word by letting everyone know about the importance of campaigns against shark finning
• Keep an open mind and educate yourself on sharks by watching educational programs or better yet, embark on shark cage diving trip.

Watch this video on how humans are destroying the ocean’s eco-system.

http://www.youtube.com/watch?feature=player_embedded&v=xVKrwsXvC0A

Source:

http://www.oceanicdefense.org/campaigns/stop-shark-finning.html