Movement patterns of whale sharks in Cenderawasih Bay, Indonesia, revealed through long-term satellite tagging

Abstract

Whale sharks, Rhincodon typus, are found circumglobally in tropical and warm temperate seas, exhibiting a range of residency and movement patterns. To determine spatio-temporal habitat use by juvenile male whale sharks in Cenderawasih Bay, Indonesia, we collected data from June 2015 to November 2016 using 16 fin-mounted satellite tags that provided exceptionally long track durations. Fifteen tags transmitted for 48–534 days (mean=321±33, s.e.), with 13 tags transmitting for ≥220 days. Four sharks remained within the bay for the duration of the study, while of the 11 sharks that travelled outside the bay, eight left between March and May 2016. They ranged throughout coastal and offshore waters, travelling up to 5144km away from Cenderawasih Bay, with a mean horizontal speed of only 3.3km day−1±0.70, s.e. A switching state space model was fitted to satellite fix data to identify behavioural states. It revealed that sharks spent an average of 81% of their time in foraging-related behaviours, mostly in shallow waters (median depth=35m), with travelling observed mainly over deeper waters (median depth=1284m). The movement patterns reveal variable periods of residency, with individual patterns of horizontal movement most likely in response to different abiotic and biotic factors, including food availability, which may trigger seasonal dispersal.