Assessing potential environmental influences on killer whale (Orcinus orca) distribution patterns in the Bremer Canyon, south-west Australia

ABSTRACT

Submarine canyons play an important role in the regional distribution, abundance and dispersal of marine biota and are increasingly being recognised as geomorphic features of high conservation significance along Australia’s continental margin. Certain canyons have been described as foraging ‘hotspots’ attributable to the high abundance of apex cetacean species aggregating in these areas. Anecdotal evidence of large seasonal aggregations of killer whales in the Bremer Canyon, south-west Australia, has attracted significant research attention in the last decade. To identify important environmental drivers influencing aggregation patterns, a predictive spatial habitat model using the Maxent model was developed based on presence-only whale sighting data. In addition, remotely sensed sea surface temperature and chlorophyll-a concentrations were assessed to investigate the spatio-temporal variation in sea surface conditions. Habitat preference was predicted in areas between canyon heads, with the most influential predictor variables being depth and distance from the continental shelf break. Analysis of remote-sensing data highlighted low localised variability in surface waters and illustrated the seasonal trends of the Leeuwin Current. This study demonstrates the influence of bathymetry and submarine geomorphology on enhanced cetacean abundance and highlights the need for recognition of this potential foraging area in marine reserve planning.

KEYWORDS:

• Killer whale
• Orcinus orca
• Bremer Canyon
• species distribution modelling
• Maxent

Acknowledgements

Glider data were collected by the University of Western Australia (UWA), satellite data were processed by the CSIRO, and both were sourced from the Integrated Marine Observing System (IMOS). IMOS is a national collaborative research infrastructure, supported by the Australian government. Bathymetric data were sourced from Geoscience Australia. The authors thank David Riggs (Riggs Australia) for providing vessel time during the research survey and provision of the volunteer-collected whale-sighting data. We also thank the two anonymous reviewers for valuable and constructive comments on the manuscript. Research was completed under University of Sydney Animal Ethics Committee protocol approval 568, Cetacean Permit C2013-0010 issued under section 238 of the Environmental Protection and Biodiversity Conservation Act 1999.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Alexandra Jones http://orcid.org/0000-0002-5565-6109

Eleanor Bruce http://orcid.org/0000-0002-7640-2335

Kevin P. Davies http://orcid.org/0000-0003-2170-7008