Acknowledgements
We thank the numerous students, research assistants and volunteers who have contributed to sample collection and processing. We also thank D. Colville for permitting the use of the spatially explicit habitat data used in our analyses, and R. Greuel for using these data to create the map featured in the manuscript, and the University of Calgary Centre for Health Genomics and Informatics for assistance with library preparation and sequencing. In-kind and logistical support was provided by the Department of Fisheries and Oceans Canada (DFO), Canada Coast Guard, the Bedford Institute of Oceanography (DFO Science), Environment Canada, Parks Canada Agency, Maritime Air Charters Limited (Sable Aviation), and Sable Island Station (Meteorological Service of Canada). Funding was provided by the Margaret Gunn Endowment for Animal Research, the L. David Dubé and Heather Ryan Veterinary Health and Research Fund, the University of Calgary, the Morris Animal Foundation (D20EQ-051), the Natural Sciences and Engineering Research Council of Canada (Discovery Grants numbers 2019-04388 to JP, 2016-06459 to PDM), and the Canada Foundation for Innovation (Leaders Opportunity Grant number 25046). MRS was supported by NSERC Vanier, Alberta Innovates, and Killam Pre-Doctoral scholarships. Sample collection and laboratory analyses were performed under Parks Canada Agency Research and Collections Permit SINP-2013-2014, University of Saskatchewan Animal Care Protocol 20090032, and University of Calgary Animal Care Protocol AC18-0078.