The tiger shark (Galeocerdo cuvier), is a charismatic but little understood species that is found in tropical and warm temperate oceans. As apex predators, they play a key ecological role in many marine ecosystems, including shallow seagrass and coral reef habitats.
Like many shark species, tiger sharks are regularly caught in both targeted fisheries, and as by-catch. While globally they are not considered at risk of extinction, there is evidence of declines in regional populations of tiger sharks. Further declines are expected in the future, as world-wide fishing activity increases and the demand for shark products grows.
The Western Indian Ocean
For the Western Indian Ocean, specifically Kenya, Tanzania and Mozambique, there is limited baseline data on shark movements and current population trends.
The Watamu Banks, off the Kenyan Coast, is a unique site where large female tiger sharks, suspected to be pregnant, are anecdotally known to aggregate each year. This localised aggregation makes them particularly vulnerable to overfishing.
Satellite tracking for research and conservation
In December 2014, with funding from Selfridges Project Ocean, ZSL joined up with partners from CORDIO East Africa and the University of Windsor in Canada, and headed out to Watamu to carry out a pilot study. The team successfully attached satellite ‘SPOT’ tags to five female tiger sharks, which via the ARGOS satellite system, transmit real time GPS positions when the animal swims near the surface.
This is the first time that data have been collected for tiger sharks in the Western Indian Ocean, and the team is already seeing some interesting movement patterns.
Future of the project
The five tags already deployed can potentially transmit data for anything up to three years. The next stage will be to carry out a second expedition to Watamu to tag more animals and begin to build a comprehensive and long-term shark monitoring programme for the Western Indian Ocean. Using this satellite technology, we can improve our understanding of both regional and global movement patterns of the tiger shark, informing the effective management and conservation of these top predators and the ecosystems they are part of.
Find out more
Read team member Fiona Llewellyn's blog to find out more about the first tagging expedition.