Yesterday I joined the CI group for a week-long dive and survey expedition to Cenderawasih Bay on the northwest end of West Papua. During the next couple of days we hope to encounter and spend some time observing whale sharks at some of the liftnet fishing boats (bagans) in the bay.
Only during the last few years has it become known that whale sharks are attracted to these bagans as they harvest small sardine-sized fish by attracting the fish at night with floodlights. Sharks are now seen regularly almost year-round near the growing number of bagans that operate in Cenderawasih Bay.
Indeed, the Indonesian government is now considering supporting the development of local whale shark ecotourism industries. To help evaluate and prepare for those opportunities, last May in Nabire I led a workshop on whale shark ecology and ecotourism in collaboration with WWF and Indonesian federal and local governments. In May I also tagged one whale shark at one of the bagans with a satellite-linked data recorder and transmitter to demonstrate one of the methods that might be used to learn more about shark behavior, and perhaps to monitor the interactions between the bagans, ecotourism activities and the sharks.
With sponsorship from CI patrons, we hope to attach telemetry tags to five more sharks during the next couple of days while we visit the bagans near Kwatisore (in the southern sector of Cenderawasih Bay National Park).
The tags we’ll be using are called pop-up archival satellite-linked tags. Once the tag is attached to the shark — with a short tether attached to a small dart tip implanted just beneath the skin surface — it remains there for a certain period of time, probably around 200 days in this case. At the programmed release date, the tag will detach from the anchored tether and float to the surface, at which point the tag will start transmitting all the data that have been collected to earth-orbiting satellites in the Argos system. Those data include frequent measurements of depth (to document diving patterns), water temperature (as one metric of vertical habitat), and ambient light levels.
Once these data are processed, we can reconstruct the movements of the sharks by calculating latitude and longitude once each day from estimates of sunrise, sunset, and day-length.
The first step is finding the sharks, so we hope to report on that and more tomorrow!