SHARKS

DISCOVER

The waters around Dyer Island has one of the densest populations of Great White Sharks in the world. Attracted by the colony of roughly 60 000 seals on Geyser Rock separated from Dyer Island by the world-famous Shark Alley, the apex predators are regularly sighted by thousands of visitors who visit the area to cage dive each year. This makes the area ideal for studying this apex predator.

Much of the life of the Great White Shark remains unknown. The Dyer Island Conservation Trust believes that Science Saves Sharks. Our team targets research actions that will enable policy makers and conservation planners to make sound conservation policy decisions that will prevent further population decline.

The Great White Shark is currently listed as vulnerable by the IUCN Red List, but plummeting numbers has put them on the brink of moving into the endangered classification. The world-wide population figure is uncertain, but estimates have suggested that only between 3 000 to 5 000 remain.

We use our dedicated research vessel, aptly named Lwazi, meaning “seeking knowledge” in isiXhosa, to carry out our research work.

Estimating white shark numbers is challenging and requires a combination of data, such as tagging, historical fisheries as well as photo identification.The Dyer Island Conservation Trust produced the first population estimate for Gansbaai in 2013 of 800-1000 individuals using photo ID and automated software. Currently, a national estimate is underway using a varied method approach

ACOUSTIC TAGGING:

Our marine biologists explore the movement ecology of sharks within the greater Dyer Island area through the use of acoustic tags. Sharks are fitted (tagged) with acoustic transmitters.

A permanent network of 13 receivers, anchored to listening stations across the greater area record shark movements via these receivers. The data gathered from the “shark tracks” allows our marine biologists to analyse shark movements. This work is done in collaboration with the African Tracking Platform, which incorporates data from all tagged species along the coastline.

SATELLITE TRACKING:

Our collaborative studies conducted together with Ocearch in 2012 revealed the larger migratory movement patterns of sharks within the bay and along the Southern African coast. To protect the Great white shark we need to understand which areas they frequent.  This knowledge could indicate possible breeding regions and areas where they face greater risks. 

Information discovered during the satellite tracking studies reveal that:

  •     The Gansbaai Great White Sharks are moving into areas such as Mozambique where they face the threat of being killed by local fishermen. 
  •     The shark nets and drumlines in Kwazulu Natal waters off South Africa’s coastline are