Tiger sharks
Project Leader: Vic Peddemors
Background
The SOSF-funded research program based at the Aliwal Shoal, South Africa is focused on exploring the behaviour, ecology and population structure of tiger sharks (Galeocerdo cuvier) through observations, questionnaires and tagging telemetry.
In the field
Vic Peddemors
Baiting stations were initially deployed to observe tiger sharks while diving, while a questionnaire was developed for the dive charter operators to complete during each tiger shark trip, providig invaluable information. Additionally, dive operators and their clients also provided photographs of sharks seen during their dives, which supplied the primary source of data for the photo-identification catalogue during 2006 and 2007. Individually coded teflon tags were also developed and have been deployed since November 2006. This technique of ‘double tagging’ i.e. both conventional and photographic tagging, is set to substantially improve the data collected in subsequent years to estimate philopatry (the tendency of an animal to stay in a particular area), and individual shark residency patterns.
18 VR2 listening stations were also deployed in a grid within the Aliwal Shoal marine protected area (MPA) for telemetry studies. Unfortunately, massive decadal storms off KwaZulu-Natal led to the loss of a substantial number of these, and a consequent loss of data for the project. 4 pop-up archival satellite tags have thus far been successfully deployed, with 2 of these sharks having returned to the reef within months after leaving.
18 VR2 listening stations were also deployed in a grid within the Aliwal Shoal marine protected area (MPA) for telemetry studies. Unfortunately, massive decadal storms off KwaZulu-Natal led to the loss of a substantial number of these, and a consequent loss of data for the project. 4 pop-up archival satellite tags have thus far been successfully deployed, with 2 of these sharks having returned to the reef within months after leaving.
Aims & objectives
Results received from the data to date are already challenging what is known about the tiger shark: greater than 95% of the tiger sharks encountered have been females, although no pups have been seen. Many of these were animals that had been seen during previous years indicating some amount of philopatry within the species.
The data collected also shows that the sharks conduct frequent dives of over 300 meters, with a record dive depth of 833 meters recorded; the fact they are also recorded swimming through changes of over 10oC also challenges the commonly held view that this is simply a ‘warm water and tropical’ species.
The data collected also shows that the sharks conduct frequent dives of over 300 meters, with a record dive depth of 833 meters recorded; the fact they are also recorded swimming through changes of over 10oC also challenges the commonly held view that this is simply a ‘warm water and tropical’ species.