Uncharted Waters

Shifts in white shark distribution along the South African Coast amid orca predation and a landmark dispersal event

South Africa’s Western Cape historically supported reliable seasonal aggregations of white sharks (Carcharodon carcharias), particularly in False Bay and Gansbaai. Since 2015, sightings have declined markedly, coinciding with the emergence of a shark-specialist ecotype of killer whale (Orcinus orca), though other factors may also be influencing this. More recently, similar declines have occurred in Mossel Bay and Plettenberg Bay, while white shark activity has seemingly increased along the Eastern Cape, particularly between East London and Chintsa, regions previously considered transitory for the species.

In May 2024, a confirmed orca predation event in Chintsa suggested a new zone of pressure, likely involving different individuals from those identified in the Western Cape. These changing patterns prompted a collaborative tagging effort. Satellite tags were deployed on white sharks in the Eastern Cape by Oceans Research, the South African Institute for Aquatic Biodiversity, among other organisations, and in Mossel Bay by the South African National Parks, Department of Environment, Forestry and Fisheries, and partners.

The presentation explores whether new aggregation sites are emerging beyond established monitoring frameworks. It concludes with an unprecedented long-distance dispersal: a white shark tagged off Dyer Island, Gansbaai, in 2012, was recently recaptured in Indonesia. This finding highlights the value of long-term tracking and cross-sector collaboration in understanding the spatial ecology and conservation needs of wide-ranging apex predators in a dynamic and changing ocean.

Each session consists of 20-minute presentations, followed by a joint Q&A session of 15 minutes.

ABOUT DR ALISON TOWNER

Dr. Alison Towner is a marine biologist with nearly two decades of experience studying sharks in South Africa. Her work focuses on the spatial ecology of white sharks and, more recently, the novel interactions between orcas and white sharks. Alison holds a BSc in Marine Biology from the University of North Wales, Bangor, an MSc from the University of Cape Town, and a PhD from Rhodes University. Her research provides critical insights into the ecological, economic, and conservation implications of predator dynamics in Southern Africa's marine ecosystems.