Humpback Whale Post Mortem Suggests Entanglement in Salmon Farm

Published Wednesday, 9th July 2014 in SAC Consulting news

Humpback whale, Mull

SRUC vets believe that a young humpback whale found drowned off the coast of Mull died after swimming into a fish farm.

The post mortem results suggest the animal became trapped under a salmon pen and subsequently drowned.

Aided by staff from the Hebridean Whale and Dolphin Trust and Aberdeen University’s Lighthouse Field Station, the post mortem was carried out by Dr Andrew Brownlow from Scotland’s Rural College, which coordinates the Scottish Marine Animal Stranding Scheme. Every year over 400 marine mammals are stranded around the coast of Scotland and any cases suitable for post mortem are examined by the project.

There have only been six recorded humpback whale strandings in Scotland since 1992 (17 in the UK) and this is the first where a post mortem has been carried out. The whale was a juvenile male, almost 7m long (23ft) and weighing just under seven tonnes (6900kg). The stomach lining suggested little solid food had been ingested in the past so it is possible that the whale was still receiving milk from his mother.

The animal was found dead beneath the nets of a salmon pen. Due to the logistics involved in recovery it was around 36 hours after discovery before the animal could be post mortemed, however it was still in relatively fresh condition and therefore a reasonably confident diagnosis could be reached. The post mortem findings are consistent with a peri-weaning, maternally-attached animal which underwent an acute death. The observed pathology and stranding history would be consistent with the whale becoming trapped beneath a salmon pen and subsequently drowning.

The report also notes that young humpback whales are very inquisitive creatures which could explain why the animal was attracted to the salmon farm located at Fishnish on Mull.

Andrew Brownlow, Head of the Stranding Scheme, says: “It is obviously very unfortunate when marine animals become entangled in this way, but it is thankfully still a relatively rare occurrence. We are still running tests on this case to investigate if there was any underlying reason which could explain this quite unusual behaviour, however it is possible this was simply a young, inquisitive, maybe hungry animal who took a wrong turning.”

All dead strandings should be reported to the Scottish Marine Animal Stranding Scheme. The strandings project was set up in 1992, led by SRUC, funded by Marine Scotland and supported by National Museums Scotland. The project aims to collate, analyse and report data for all marine mammals (cetacean and seals), marine turtle and basking shark strandings.

For more information, or a photograph, please contact Andrew Brownlow (01463 246044 / andrew.brownlow@sruc.co.uk) or Sarah Hunter-Argyle.

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