Matthew Dicken

A Preliminary Investigation into the Size, Sex and Seasonal Ocurrence of White Sharks (Carcharodon Carcharias) within the Bird Island Marine Protected Area

White shark observed underwater at Bird Island.

Surface view of white shark at Bird Island.

Bird Island's Ganet Colony.

Shark biting on seal decoy.

Underwater photo of shark.

Shark approach underwater.

Town/RegionCountryCategoriesDate
Bird Island, Algoa Bay, Eastern CapeSouth AfricaAfrica, Fish, Marine9 Sep 2009

This project focuses on juvenile white sharks and investigates the possibility that the Bird Island MPA and inshore regions of Algoa Bay are nursery or pupping grounds for white sharks in South Africa. This information is crucial not only to improve our understanding of white shark biology, but also for their long-term management and conservation in South Africa, particularly within the Bird Island MPA.

Bird Island is one of a cluster of four islands, which constitute the Bird Island group in Algoa Bay. It was proclaimed a Marine Protected Area in 2005 and is thought to be an epicentre of white shark abundance. As a result, it has been earmarked for a cage diving permit. Existing white shark research in South Africa has focused almost exclusively on the adult component of the population in the Western Cape and KwaZulu-Natal. Although there have been no previous scientific studies on white sharks in Algoa Bay this region has the highest number of recorded catches for small (< 160 cm) sharks, in South Africa. This is close to the reported birth size for white sharks of 1.5 m.

We aim to collect baseline data on the size, sex and seasonal occurrence of white sharks within the Bird Island MPA by conducting monthly boat trips to the island over a 12-month period. Photos of sharks will be taken using a camera mounted with a fixed space laser pointer. This will allow reliable size estimates of sharks to be recorded. Sharks will be attracted to the boat for ID purposes using standard chumming practices used by other white shark researchers in South Africa. Sharks will be I’D from dorsal fin photos and from unique pigment patterns on the gill flaps, pelvic fins, and caudal fins. Shark sightings will be correlated with environmental conditions such as temperature, turbidity and current strength & direction.

This project is a preliminary study, which we hope will form the platform for a much larger and more integrated multidisciplinary project in the future. It is a project we hope to develop over the next 5 to 10 years with the inclusion of ultrasonic and satellite tagging as well as socio-economic studies related to the development of a proposed cage diving operation in the region.

For further information contact raggedtoothshark@bayworld.co.za

Project Update: December 2009

In November and December 2009 we conducted our first two trips to the Bird Island MPA where we observed a total of three white sharks ranging in size from 2 to 4 m. White sharks are rarely seen around seal colonies in the summer months, preferring to hunt on fish close inshore. As a result, we were pleased to observe even a few sharks.

We have monthly trips planned to the MPA for the next 10 months and are expecting to see increased numbers of white sharks as we progress into the winter. The seals on Black Rocks started to pup in November. It is these young seals, which the sharks will begin to predate on in the coming months.

The project has begun to generate a lot of local interest. The South African Environmental Observation Network (SAEON) has facilitated the use of their research boat and we are hoping that the local Metro will become involved in the future.

Project Update: April 2010

Attached is a poster (on the white shark project) that I recently presented at the opening of the South African Environmental Observation Network, in Port Elizabeth, South Africa.

File DownloadSize
Poster.doc840 KB
Project Update: September 2010

A total of nine trips have been made to Bird Island to chum for sharks between November 2009 and September 2010. Interestingly sharks have only been observed in the winter months (May to September). As many as six different sharks have been observed in any one day, ranging in size from 1.5 to 4.5 m. Photographs of unique dorsal fin and pigmentation patterns have been used to identify individual sharks. To date, 10 different sharks have been positively identified and seen on multiple trips. We anticipate that a greater number of sharks will be photographed in the future to build a photographic library of sharks within the Bird Island MPA. The capture of sharks by fishermen close inshore during the summer months and sighting of sharks around Bird Island during the winter suggests a seasonal offshore movement pattern. A similar pattern has been recorded for white sharks in the Western Cape.

Final Report

Read more about the activities undertaken and findings of this project in the final report and report attachments below.

File DownloadSize
Final Report.doc702 KB
Fig 1 - Chumming locations.jpg1.44 MB
Fig 2a - Shark pictures.doc143.5 KB
Table 1 - Bird Island shark summary.doc53.5 KB

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