Dear MARMAMers
‘Corkscrew’ mortalities have been occurring in some harbour and grey seal populations around the UK, where dead seals with characteristic spiral wounds are found on beaches. All of the seals
have a characteristic wound consisting of a single smooth edged cut that started at the head and spiralled around the body. The wound was identified as the cause of death in all cases for which a detailed post-mortem examination was carried out. Post-mortem
examinations of a number of harbour seals revealed they had been alive and healthy when the injuries were sustained, with no evidence of any underlying disease or disability (Bexton
et al. 2012).
Based on the pathological findings it was concluded that mortality was caused by a sudden traumatic event involving the strong rotational shearing force of a rotating blade. The injuries were
consistent with the seals being drawn through a ducted propeller (Thompson et al., 2013). Other causes of death have been ruled out.
A number of severely damaged seal carcasses had been found on beaches in eastern Scotland around St Andrews Bay, Tay and Eden Estuaries and the Firth of Forth, on Orkney in the Northern Isles,
along the North Norfolk coast in England, and within and around Strangford Lough in Northern Ireland. Investigations, funded by the Scottish Government, have been underway for some time:
http://www.smru.st-andrews.ac.uk/pageset.aspx?psr=152 Some references are provided below.
We are aware that similar mortalities have occurred in eastern Canadian waters. We are aware of incidences in the Philippines historically, although we have no evidence of this at present. It would seem strange
that such mortalities are not occurring elsewhere and so, are interested to find out if such injuries have been identified in other parts of the world, and to find out about the types of vessels involved and any effective technical solutions.
I would be grateful if you would get in touch with me at
sarah.dolman@whales.org if you have any information at all about occurrences of these injuries in other parts of the world, vessels involved and any efforts to successfully prevent these deaths.
Thanks,
Sarah Dolman
Northeast Atlantic programme manager
Whale and Dolphin Conservation
Some relevant references:
Bexton, S., Thompson, D., Brownlow, A., Barley, A., Milne, R. and Bidewell, C. 2012. Unusual Mortality of Pinnipeds in the United Kingdom Associated with Helical (Corkscrew)
Injuries of Anthropogenic Origin. Aquatic Mammals 2012, 38, 229-240.
Brownlow, A. 2013. Spiralling trauma? Describing a novel form of pinniped mortality in the United Kingdom. Abstract submitted to and presentation made at the 27th
European Cetacean Society Conference, Setubal, Portugal.
Thompson, D., Culloch, R. and Milne, R. 2013. Current state of knowledge of the extent, causes and population effects of unusual mortality events in Scottish seals.
Report to Scottish Government. Marine Mammal Scientific Support Research Programme MMSS/001/11. Available online at:
http://www.smru.st-and.ac.uk/documents/1282.pdf
Thompson, D., Bexton, S., Brownlow, A. and Wood, D., Patterson, T., Pye, K., Lonergan, M. and Milne, R. 2007. Report on recent seal mortalities in UK waters caused
by extensive lacerations. Available online at: http://www.smru.stand.ac.uk/documents/366.pdf
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Sarah Dolman |
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