Marine Evening: White Sharks of Gansbaai

March 29, 2017 Brenda du Toit

The waters of Gansbaai are believed to have one of the of White sharks in the world. With the opportunity to see this shark all year round, and the proximity to land making it one of the most accessible places in the world to do so, Gansbaai is on the top of many tourists list's to visit in the hopes of catching a glimpse of this animal. These factors also allow for critical studies to be undertaken on this legendary but little known about shark species. The nearly daily trips run allow a platform to consistently conduct crucial observational studies, collect photo-identification and measure environmental parameters leading to a better understanding of the white shark as the simple fact is, to date, knowledge is limited concerning this animal, including vulnerability status and we cannot possibly hope to protect, conserve and provide a realistic image on something we know so little about.

It was with this in mind, that Marine Dynamics’s biologist, Kelly Baker, shared her observations of three years on board Slashfin. Kelly holds a Bachelor of Biological Science from the University of Wollongong, New South Wales, Australia. Her long term daily observational data is adding extensively to the current database on file for the Marine Dynamics/Dyer Island Conservation Trust team. Her main areas of focus include determining the size and thus growth rates of the sharks that visit and revisit the area; documenting wounds, healing and scars and the identification of individuals using the dorsal fin - in turn monitoring the population as a whole.

As Kelly said, “The growth and maturity rates of an animal are important pieces of information that can be related to the risk of population decline as a species especially as slow growth and a long time to mature in white sharks means the risks of population decline and pressure from threats is a real concern. White sharks are also known to demonstrate rapid rates of healing. A prime example is a shark we call Scarlett who we saw with bite wounds to her head and caudal fin in 2015. She returned in 2016 healed and with little scarring. She appeared in good condition and was not impeded by her injury.”

Observations like this are important in understanding the healing process and how sharks may cope with scientific studies such as tagging and biopsy. Kelly explained the daily data taken off the boat – temperature (average 10 to 20⁰C), pressure (very little fluctuation) and oxygen levels (4-9mg/l). Low levels of oxygen will place stress on marine life and with temperature seen to affect sightings and behaviour of white sharks in previous studies (Towner et al 2012) – males thought to prefer the cooler side of range, females seek out warmer waters – this kind of information is critical to our understanding of behaviour.

Kelly closed with a few of the iconic sharks and her personal favourites of the area - Pieter, Mini Nemo, PJ and Inrid - which left everyone feeling like they knew that much more about the white sharks of Gansbaai.