Gauging the threat

The first ever study of the white shark population of Dyer Island (Gansbaai, South Africa), widely accepted as being the great white shark capital of the world.

Posted Thursday, December 28, 2017

Project Background

Great white sharks are an endangered species, considered vulnerable across the globe due to declining numbers.

With this in mind, you’d be forgiven for assuming that an actual population estimate for what is widely considered the ‘White shark capital of the world’ would already exist. After all, how can one determine whether or not an animal is truly endangered, in lieu of data from such a vital resource?

Well, apparently – with relative ease – as no such study had been done for said White shark capital; Gansbaai (Dyer Island, specifically), South Africa.

Despite a number of population studies having been begun (some abandoned without publication entirely), none had been completed by 2012, which was around the time I was fleeing Mossel Bay for fear of an ever hastening decline into total insanity.

I had friends working for Marine Dynamics in Gansbaai, who informed me that such a study was underway, but they were desperately low on manpower to simply crunch data for the five year period over which it had been collected. Given I was without occupation, fairly used to spending an unhealthy amount of time behind a keyboard and likewise desperate to say involved with anything remotely sharky, this seemed like the perfect pairing.

I dragged my better half along to assist with their videography/photography department and this move culminated in ‘Gauging The Threat‘, the world’s first official publication on the white shark population of Gansbaai, South Africa.

My role on the project

My job was to look at shark fins… hundreds and hundreds of shark fins.

Not due to some bizarre fetish (coincidence, I assure you), but because for this particular study, shark dorsal fins were determined as being the best (in terms of practicality, cost and efficiency) means of identifying individual animals, given that no two fins are the same.

While that’s true, in many cases the variants between individuals’ fins can be so subtle, that you’d be forgiven for thinking they were the same. This is true to such an extent that even the software we were using to collate these fins (designed to identify and match shapes) likewise struggled, often pairing fins with hundreds of potential matches wherein some cases – absolutely none were correct.

This process needed a keen, human eye. While my suitability to the latter prerequisite is debatable, there was no question that this is something I was enthusiastic to do.

I’m familiar with the general notch shapes, rosies and wounds which appear on shark dorsal fins, so once I got into the swing of things I was able to identify a surprising amount within an initial glance, relying on the software moreso for cataloging than the identification process.

What was really interesting was seeing how some of the fins changed over time. Many of the individual sharks came back to the area at similar times year on year, so observing how certain shapes had changed through wounds healing, being incurred and the general growth of the animal, added an interesting element to the process.

It also made it an absolute ballache to identify individuals whose fins had changed significantly.

Anyhow, we finished the study towards the end of 2012, publishing and presenting our findings in June 2013. We’d concluded that an approximated total of 1008 individual white sharks had passed through Gansbaai, down almost 50% on previous projections.

Happy days.