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Diseases of Aquatic Organisms

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DAO 139:81-86 (2020)  -  DOI: https://doi.org/10.3354/dao03473

NOTE
Inferring diet, feeding behaviour and causes of mortality from prey-induced injuries in a New Zealand fur seal

D. P. Hocking1,2,*, F. G. Marx1,2,3, W. M. G. Parker1,2, J. P. Rule1,2,4, S. G. C. Cleuren1, A. D. Mitchell5, M. Hunter6, J. D. Bell7,8, E. M. G. Fitzgerald1,2, A. R. Evans1,2

1School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
2Geosciences, Museums Victoria, Melbourne, Victoria 3001, Australia
3Museum of New Zealand Te Papa Tongarewa, Wellington 6011, New Zealand
4Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
5Department of Environment, Land, Water and Planning, Orbost, Victoria 3888, Australia
6Gembrook Veterinary Clinic, Gembrook, Victoria 3783, Australia
7Victorian Fisheries Authority, Queenscliff, Victoria 3225, Australia
8Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7004, Australia
*Corresponding author:

ABSTRACT: New Zealand fur seals Arctocephalus forsteri are the most abundant of the 4 otariid (eared seal) species distributed across Australasia. Analyses of stomach contents, scats and regurgitates suggest a diet dominated by bony fish and squid, with cartilaginous species (e.g. sharks and rays) either absent or underrepresented because of a lack of preservable hard parts. Here we report on a subadult specimen from south-eastern Australia, which was found ashore emaciated and with numerous puncture wounds across its lips, cheeks, throat and the inside of its oral cavity. Fish spines embedded in the carcass revealed that these injuries were inflicted by chimaeras and myliobatiform rays (stingrays and relatives), which matches reports on the diet of A. forsteri from New Zealand, but not South Australia. Shaking and tearing of prey at the surface may help to avoid ingestion of the venomous spines, perhaps contributing to their absence from scats and regurgitates. Nevertheless, the number and severity of the facial stab wounds, some of which led to local necrosis, likely affected the animal’s ability to feed, and may account for its death. Despite their detrimental effects, fish spine-related injuries are difficult to spot, and may be a common, albeit cryptic, type of trauma. We therefore recommend that stranded seals be systematically examined for this potentially life-threatening pathology.


KEY WORDS: Arctocephalus forsteri · Elephant fish · Stingray · Injury · Pinniped · Prey processing


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Cite this article as: Hocking DP, Marx FG, Parker WMG, Rule JP and others (2020) Inferring diet, feeding behaviour and causes of mortality from prey-induced injuries in a New Zealand fur seal. Dis Aquat Org 139:81-86. https://doi.org/10.3354/dao03473

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