Research led by the Wildlife Conservation Society (WCS) and the Instituto Oceanográfico de Moçambique (InOM), using baited remote underwater video (BRUV) surveys to assess sharks and rays off southern Mozambique, has recently recorded a tagged young white shark matched to an earlier record of the same individual in a BRUV survey off Struisbaai, in South Africa, in May 2022. Distinct facial scars and caudal fin coloration matched, as well as the position of the tag confirming the same individual shark, a juvenile male, in both records.
Shark and ray species are under immense pressure globally from fisheries. These surveys are conducted to identify ecologically important areas for shark and ray species, to help inform improved management measures for these threatened species.
The surveys in Mozambique, conducted by Dave van Beuningen (WCS), Jorge Sitoe (WCS), Emildo Notisso (InOM) and Jonas Chambo (Ocean Revolution Mozambique), are part of a broader initiative using BRUV technology to identify shark and ray hotspots throughout the southwest Indian Ocean. The surveys are led by WCS and InOM, in collaboration with Ocean Revolution and the South African Institute for Aquatic Biodiversity, and are funded by the Shark Conservation Fund. The white shark tagging in South Africa is part of a PhD project lead by Alison Towner of Rhodes University, and the BRUV surveys in South Africa were conducted in collaboration with Hazmat Productions and Discovery Channel.
Rhett Bennett, PI on the BRUV survey project in Mozambique said: “This single observation is of great value to shark science and conservation, as it confirms a transboundary movement, on the scale of thousands of kilometers, of a threatened shark species, which has major implications for the management of this species. The individual ID match also highlights yet another value of BRUVs, and specifically video records, as useful research tools for shark and ray science.”
The BRUV surveys are conducted by deploying a “pair” of stereo video cameras from a small boat, with a bait container attached to the camera frame. The bait attracts predatory fishes, such as sharks, which are filmed when they enter the camera’s field of view. In addition, the stereo video cameras have their fields of view calibrated, allowing accurate estimates of the size of any animal passing by. The original sighting of this individual was made during surveys off Struisbaai in South Africa, near the southern tip of Africa, and the “re-sighting” observation was made during a survey off Chidenguele, in southern Mozambique.
The findings will help to inform fisheries and resource managers in South Africa and Mozambique about the migratory capacity of white sharks, and the need for multilateral or at least bilateral management measures for this and other threatened shark and ray species that are moving between the waters of these countries.
Alison Towner, PI white shark tagging study in South Africa said: “This important ID match and confirmation of transboundary movement has come at a time that the Southern African white shark population is facing the additional threat of orca predation on top of other anthropogenic threats such as shark nets. It’s a great example of collaboration between different research platforms.”