Natural and Artificial Structures Influence the Movement and Habitat Connectivity of Whale Sharks (Rhincodon typus) Across Seascapes

Abstract

Aim

To understand how natural geomorphological features and oil and gas platforms (OG platforms) influence the habitat use and seascape connectivity of the whale shark (Rhincodon typus).

Location

East-Indian Ocean and North-West Australia.

Methods

We compiled a satellite tracking dataset of 78 whale sharks tagged across a 14-year period at Ningaloo Reef and Shark Bay World Heritage Areas in Western Australia to develop spatial networks for the regions of the East-Indian Ocean and North-West Australia. We then applied a Bayesian modelling framework to assess the effects of natural features and OG platforms on spatial patterns and habitat connectivity.

Results

Geomorphological features such as pinnacles, canyons, and seamounts promoted habitat connectivity and strongly influenced the habitat use of whale sharks across both regional (1000's km; East-Indian Ocean) and local (100's km; North-West Australia) spatial scales. In the North-West of Australia, OG platforms had similar effects on habitat use as natural feature types and also enhanced habitat connectivity. The OG platforms most visited by whale sharks were situated close to the edge of the continental shelf and near natural geomorphological features that likely enhance productivity.

Main Conclusion

Our work identified natural geomorphological features that promoted habitat use and connectivity for whale sharks across oceanic and coastal seascapes. Sharks routinely visited OG platforms, which acted as migratory stepping stones that further enhanced habitat connectivity. Protection of natural feature types that promote habitat use and connectivity could assist conservation management of whale sharks. We suggest that the influence of OG platforms on their movement and habitat use beyond individual structures, should be considered in environmental impact assessments during operation and decommissioning phases.