Whale sharks, Seychelles
Project Leader: David Rowat
Read the project blog here.Background
The Marine Conservation Society Seychelles (MCSS) has been conducting monitoring and research into the occurrence of whale sharks around Seychelles since 1996. With sound scientific guidance and support from a number of organisations including SOSF, the MCSS whale shark program has already revealed a huge amount of information on the species, including the seasonal occurrence of sharks around the main island of Mahe and the identification of their most frequented localities.
In the field
David Rowat
The research is led by David Rowat, a highly experienced diver and field worker, who is co-director of the Seychelles Underwater Centre, and chairman of the MCSS. Marker tagging and photo identification studies from 2001 to 2006 have already identified 468 individual sharks of which 55 were seen over a period of several years. Population estimates indicate a resident population of 150 to 180 sharks that are joined annually by large numbers of transient sharks. Daily aerial surveys have shown that the occurrence of the sharks is limited both temporally and spatially, and that there are preferred ‘hot-spots’.
Aims & objectives
Data from pop-off satellite archival tags (PSAT) have recently shown that the species spends up to 60% of its time less than 10 meters from the surface, but that they are also able to make dives in excess of 1,000 meters. That said, these satellite-tracking studies have been fraught with problems since the sharks have shown an innate ability to remove their tethered tags.
What data that has been gathered has also revealed that the sharks often migrate away from Seychelles in very divergent directions, even when tagged just minutes apart in the same feeding aggregations. Some of these migrations have recorded distances of travel in excess of 3,600 kilometers, passing through the territorial waters of many countries in the Indian Ocean. As international concern for effective conservation and management of migratory shark species grows, it is becoming increasingly important to have accurate information about the migration routes of the species concerned.
The development of a robust satellite tagging methodology has now become a priority, and if successfully field tested it has the potential to generate wide reaching implications throughout the research community. Through the generation of data based on whale shark movements throughout the entire Indian Ocean, this project subsequently aims to develop into a cornerstone for an ocean-wide monitoring program.
What data that has been gathered has also revealed that the sharks often migrate away from Seychelles in very divergent directions, even when tagged just minutes apart in the same feeding aggregations. Some of these migrations have recorded distances of travel in excess of 3,600 kilometers, passing through the territorial waters of many countries in the Indian Ocean. As international concern for effective conservation and management of migratory shark species grows, it is becoming increasingly important to have accurate information about the migration routes of the species concerned.
The development of a robust satellite tagging methodology has now become a priority, and if successfully field tested it has the potential to generate wide reaching implications throughout the research community. Through the generation of data based on whale shark movements throughout the entire Indian Ocean, this project subsequently aims to develop into a cornerstone for an ocean-wide monitoring program.