Abstract
Northern fur seals (Callorhinus ursinus) are a pelagic species, residing in the open ocean and using offshore islands for pupping and breeding.5,6,7 Most breeding colonies are in the Bering Sea; with smaller rookeries on San Miguel and Farallon Islands.5 This habitat range differs from coastal pinniped species commonly cared for in rehabilitation facilities.1,2,3,4 Given the difference in life history and habitat use in California populations, it is hypothesized that causes of strandings in northern fur seals (NFS) will differ from coastal species. The objective of this study is to utilize stranding data, medical records, and postmortem findings to determine causes of stranding in NFS from central and northern California. A retrospective record review of live NFS admitted to The Marine Mammal Center (Sausalito, CA) spanning a 45-year period was conducted, during which time a total of 481 NFS were admitted. Pups (<1 year) comprised 87% of admits, followed by adults (10%), yearlings (2%), and subadults (1%). Causes of pup stranding included malnutrition (97%), trauma (1%), infectious disease (1%), and unknown (1%) with 26% overall mortality. Causes of stranding of remaining age classes included biotoxin (68%), trauma (16%), infectious disease (8%), malnutrition (5%), and unknown (3%) with 65% overall mortality. In 2015, 23% of strandings occurred and correlated with a large, persistent warm water event extending from Alaska down the Pacific coast to Mexico. The results of this study help to elucidate the impact of human and climactic factors on the stranding of NFS for utilization in species conservation efforts.4
Acknowledgements
The authors thank the staff and volunteers at The Marine Mammal Center for their invaluable contributions to this project and their efforts in pinniped rehabilitation and conservation. In addition, the authors thank Shelbi Stoudt and Mariah Tengler for assistance with case identification.
*Presenting author
+Student presenter
Literature Cited
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