Initiating Pop-Up Satellite Tagging of White Sharks (Carcharadon archarias) in South Africa
Mike Meyer1, Ryan Johnson2, Herman Oosthuizen1, Michael Scholl3, Stefan Swanson2, Mike Patterson1 and Deon Kotze1
1 Marine and Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Roggebaai 8012, South Africa
2 Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
3 Department of Zoology, University of Cape Town, Cape Town, South Africa
Following the protective legislation afforded to the white shark (Carcharadon carcharias) in 1991, South Africa initiated an intensive research program to establish data on the white shark. The objectives were to investigate the life history and population status of the white shark in South Africa, identify and manage threats to the white shark and produce effective and comprehensive conservation and management plans for this much-maligned species.
Due to concern over a strongly suspected
decrease in numbers of white shark populations,
South Africa was the first country to institute
protective legislation for the white shark (1991).
Photo courtesy of Michael Scholl
Aerial picture of Mossel Bay, South Africa. The
"X" marks the spot where the white shark was
tagged on 24 July 2001. Just to the right is a
recreational area where bathers and great
whites swim!
Photo by Euward Louw
The Pop-up tag is attached using a modified spear gun.
Photo courtesy of Michael Scholl
South Africa possibly represents the healthiest regional population of white sharks in the world. In a recent research expedition, 69 individual white sharks were observed during only five days of chumming, while our photographic identification program identified over 600 individual white sharks in its inaugural two years. Despite these positive findings, a number of real concerns still exist regarding the sustainability of this population locally and globally.
Satellite tagging of white sharks is one of the technological advances that would enable us to resolve a number of issues for management and conservation of this species. Recent genetic studies have indicated the possibility of migration of male white sharks between Australia and South Africa, while suggesting female are philopatric. If true, this discovery potentially necessitates multilateral management and conservation agreements between states regarding this species. A further issue that can be resolved using this technology is the comparative rarity of mature white sharks observed during research expeditions. Is this scarcity of mature white sharks a result of a young population, or is it due to observation of a nonrandom sample of the population?
The world conservation union has identified fisheries (such as targeted bather protection nets and accidental capture in purse seine netting or on long lines) as potentially non-sustainable harvesting of the white shark stocks. This harvesting still exists in South Africa despite protection. Through satellite tagging, we can understand the spatial and temporal patterns in habitat utilization of white sharks. If areas where white sharks aggregate to breed, nurse or feed can be identified, then these areas can be afforded some protection from those identified fisheries.
Following protection in 1991, a white shark cage diving industry began in South Africa. The pop-up satellite tag technology, as part of an ongoing impact assessment of this industry, enables us to investigate the movement of white sharks between cage diving locations as well as to estimate the overall exposure of individual sharks to this industry.
The study of the movement and habitat utilization of the white shark presents a number of unique logistical difficulties. Capture and release of white sharks is very undesirable, not only due to ethical considerations, but also due to the unknown survival rate of white sharks following capture. Attachment and retrieval of instruments must be accomplished while the shark is free swimming. Furthermore, the white shark is elusive, creating the possibility that we will not re-encounter an individual following tagging. Pop-up satellite technology addresses these requirements in every way. Not only are we able to attach the tags on to free swimming animals, but retrieval of data does not require the animal to be located.
The research team arrived in Mossel Bay on 23 July 2001, and boarded the sailing vessel Infante belonging to Roy and Jackie Portway (Shark Africa). Ryan Johnson, Michael Scholl, Mike Patterson and Stefan Swanson constituted the field team. On 24 July, the team finally observed a large female shark close to 450 cm in length, and shortly afterwards, the tag was successfully attached on the shark with a modified spear gun. This Pop-up Tag will remain attached to the shark for a year. On 1 July 2002, the tag will detach itself automatically from the shark, and “pop-up” to the surface, where the tag will link to the Argos satellite system and download all the information archived over the year. During that one-year period, the tag will record water temperature and the depth at which the shark is swimming. Additionally, the tag will also record the amount of light surrounding the shark, and from that determine sunrise and sunset times. Knowing these two times, it will be possible to calculate the position of the shark on a map. This positioning system is not as precise as the position obtained with a GPS, but this system is more reliable as the shark does not have to break the surface and much more information about the whereabouts of the shark is stored. This is a first in South Africa, and most probably not the last! Depending on the results of this first attempt, the project probably will deploy several more tags such as these Pop-up Satellite tags in 2002. We are very optimistic and hopeful that this kind of technology will shed light on a number of mysteries concerning the white shark.
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