Exploring Whale Shark Movements in Indonesia
Reaching a maximum length of 18 metres and weighing up to 21 tons, the whale shark (Rhincodon typus) is the world’s largest fish and is found circumglobally in tropical and temperate seas. Though we know surprisingly little about the natural history and behaviour of these massive animals, they are known to aggregate seasonally in large numbers at specific areas around the globe, usually in order to take advantage of a temporarily abundant food source such as the fertilised eggs from mass spawning of corals or fishes.
A whale shark displaying a finmount satellite tag attached on the dorsal fin.
Image credit: Mark Erdmann
One such recently documented whale shark aggregation is in Cendrawasih Bay in the Bird’s Head Seascape of West Papua. Scientists from Conservation International and the State University of Papua have been studying this aggregation since 2010 in order to better understand the size of the population and whether these animals remain largely within Cendrawasih Bay or if they frequently migrate further afield.
Since mid-2015, Conservation International has pioneered the use of finmount satellite tags on the whale sharks of Cendrawasih – allowing much more high resolution tracking of the movements of these sharks than was previously possible using standard “pop-off” archival satellite tags. With the generous support of guests of Australia’s True North expedition vessel, Conservation International has deployed 23 finmount satellite tags on whale sharks in Cendrawasih Bay, and has uncovered a wealth of information about both the horizontal movements of these sharks as well as their diving behaviour.
Contrary to initial observations that the whale sharks of Cendrawasih appeared to be largely “homebodies” that remained in the bay year round, the satellite tagging has revealed that many individual sharks make significant journeys out of the bay – some as far away as Yap or northern Australia – before returning to the bay to feed on the abundant schools of baitfish in the water there. The tagging has also revealed that the sharks make frequent deep dives below 1000 metres depth – occasionally going as deep as 1800 metres or more!
Map of the horizontal movements of a 6 m male whale shark over a one-year period. Green dots indicate positions transmitted by the satellite tag at the beginning of deployment, while progressively darker dots indicate more recent positions. This shark spent nearly 7 months in Cendrawasih Bay before moving out and around West Papua and then down towards northern Australia.
The University of Adelaide is proud to join forces with Conservation International in this ground-breaking study. Six additional finmount satellite tags are being deployed on whale sharks in Kaimana (in the southern Bird’s Head Seascape region) and in Sumbawa, in order to get a glimpse into the behaviours of sharks from these nearby regions and determine if they are actually part of one large population in eastern Indonesia.
Once deployed, the data from these satellite tags will be displayed on Conservation International’s “whale shark tracker” webpage, allowing the general public to track the movements of these sharks in near real-time. Look for more updates on this exciting new collaboration in the coming months!
A close-up view of the finmount satellite tag attached to a whale shark dorsal fin.
Image credit: Mark Erdmann