Tagging and Genetic Analysis
The tagging studies undertaken by the Maldives Whale Shark Research Programme, in collaboration with Hubbs-SeaWorld Research Institute (California), are designed to help determine the sharks migratory behaviour, dive profiles/depths and time spent in any given habitat. The information obtained will enable the team to design effective protection methods within the Republic of Maldives and possibly further afield, if the sharks are venturing away from the archipelago.
The common miss conception about these tags - "so you can track them and find them when you want". The answer is NO. These tags do not allow realtime data to be collected. They are essentially a dive computer that stores the data until such time as the tag is recovered. The data can then be downloaded and analyzed.
Because whale sharks spend so much of their lives far from our range of detecting and observing them, tagging and telemetry is a key tool for learning about the basic biology, movements, and habitat needs of these elusive animals. This information is critical for conserving, protecting and managing whale sharks and the various elements of the marine ecosystems that they travel through and feed and reproduce in. The objective of the project is to obtain and provide this information to the Maldivian government agencies that have authority for managing marine resources and to the Maldivian public, non-governmental organizations, and other stakeholders who have interests in using and maintaining vital marine ecosystems throughout the Maldives archipelago.
Preliminary results from the tagging program have emphasised the logic and importance of this approach. It has revealed that whale sharks that spend at least parts of their lives in the Maldives are highly mobile, travelling vast distances and sometimes into unprotected waters on the high seas and other states where they can be vulnerable to fishing and fining attempts.
A large part of the MWSRP's tagging project is to monitor the behaviour of individual sharks before and after being tagged (both of tagged and untagged individuals).
Studies so far
Ten tags were deployed to a total of 8 individuals (Five archival tags and Five satellite tags) in April 2008. This was the first whale shark tagging project undertaken in the Maldives. The team returned to the Maldives in April 2009 to carry out a follow up study. Together the team deployed ten Satellite and ten Archival tags to a total of seventeen sharks. Some of the individuals tagged in the follow up study were previously tagged sharks, making the total number of tagged individuals twenty two over the two studies.
Both types of tags are attached to the dermal layer of the whale shark (just under the skin), anchored in place with a titanium plate and both record time, depth, temperature and light levels at regular intervals. (Below left is an example of a Satellite tag, below right are three examples of Archival tags [the tag on the far right has a green balloon attached to keep it positively buoyant, just in-case the tag does not attach to the shark]) .
Satellite (Pop-up) tags
Satellite tags are programmed to release from the sharks after a predetermined time frame. Once the tag releases, and breaks the sea surface, it will send the data to the team via satellite.
The tags are designed with two fail-safes: a pressure release system, preventing the tag from being crushed (one tag released from a shark at 1250 metres). The other fail-safe is a constant depth release. If a shark remains at a constant depth for a predetermined time, the tag will release. Unfortunately this fail safe is designed in-case the shark dies and remains on the sea bed (shark carcasses sink). The tag releases to salvage the stored data.
Archival tags require retrieval. Once the shark is re-spotted a member of the research team will free dive close to the shark and will cut the tag's tether. The data from the tag will then be downloaded in the laboratory.
A Satelite tag attached to a whale shark
The tags will help us understand where the sharks go and when, and what their preferred environment is. By overlaying this information with other environmental data, we are able to design a reasonable hypothesis as to why the habitats are favoured. All of this information helps us to better understand how to best protect the habitats which the sharks require.
Although we are awaiting the full results from these tags the preliminary results are looking exciting. For example, already we are able to see how the whale sharks movements may track those of zooplankton.
Genetic Analysis
Skin samples taken from the whale sharks in the Maldives enables us to examine the population's relationships with other whale sharks that appear in seasonal aggregations in the Persian Gulf, the Gulf of Oman, along the Arabian Peninsula, in the Red Sea and off the eastern coast of Africa and elsewhere in the Indian Ocean. A skin biopsy tip is used to extract a small skin sample from sharks. The skin sample is approximately 5mm in diameter and 1 - 2mm deep. (Below is a photograph of a skin sample biopsy tip.)
