A WHALE which was part of a pod at the centre of rescue attempts in the Gare Loch earlier this month has been found dead.
Experts have identified the animal as one of the northern bottlenose whales involved in a 'herding' operation on October 1 near Faslane naval base.
Specialist teams from the British Divers Marine Life Rescue (BDMLR) organisation, along with MoD officials and civilian boats, attempted to herd the pod to safer, and deeper, waters - and away from the military exercise Joint Warrior which brought increased activity around HMNB Clyde.
However, their efforts proved unsuccessful, with rescue teams saying they would "continue to monitor both the area and the whales' behaviours and movements and reassess the situation if required".
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Up to five whales were believed to have been spotted in the Gare Loch area, one of which was understood to have been in poor health and has now been recovered on a Firth of Clyde coastline.
An update shared by the Scottish Marine Animal Strandings Scheme (SMASS) group on Sunday evening confirmed the stranding, which is part of a cluster of five whales to have been found dead in recent weeks.
The update said: "The first two cases were Sowerby’s beaked whales (Mesoplodon bidens), both live stranded on the Lothian coast and were necropsied at the National Museums of Scotland, Edinburgh.
"These were both sub-adult males with significant trauma from the stranding process, but no other clear underlying infection or disease and, thankfully, no indication of entanglement, boat strike or ingestion of marine debris.
"Neither animal had fed recently but both were in reasonable body condition, suggesting an acute cause of death.
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"Notably, both animals showed an unusually high number and distribution of gas bubbles throughout the tissues- especially lung, liver and intestinal mesentery.
"Whilst gas bubbles are not an uncommon finding during post mortem examinations, and can be a result of either decomposition or emphysema from the stranding process, a large number of bubbles, especially in deep diving species such as beaked whales, is suggestive of nitrogen emboli and decompression sickness (DCS).
"Given how sensitive beaked whales are to underwater noise, specifically naval sonar, we have to consider noise-mediated DCS as a possible cause for these two strandings. We are therefore in the process of trying to find data on sources of noise in this region, including putting a request for activity logs to the MoD following the recent Joint Warrior naval exercises.
"The last three cases were northern bottlenose whale (Hyperoodon ampullatus) strandings; one in the Western Isles and two in the Clyde sea lochs.
"All were sub-adult animals, showing indications of live stranding but no evidence for disease or other trauma, entanglement, boat strike, plastic ingestion and no clear indication of DCS.
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"Unlike the Sowerby’s, all these cases were reasonably decomposed which limits what diagnostics we can run, and unfortunately pretty much rules out any assessment of noise overexposure.
"One of the animals stranded in the Clyde had been positively identified as one of animals seen around the Clyde for the past couple of months, and this animal in particular was not in great body condition, had not fed recently and was dehydrated.
"Northern bottlenose whales are deep-water specialists where they hunt in deep ocean canyons, predominantly for squid.
"Whilst some areas of the Firth of Clyde are over 1,000ft deep, these sea lochs are not their typical habitat and it is not clear how much prey these loch regions can provide.
"It’s a worrying possibility that, as their prey decrease into winter, unless the remaining animals make it back out to open sea, we may see more strandings.
"We’ve certainly had more than the usual number of beaked whale strandings over the past few years and it is becoming quite clear just how important our waters are for these species: species we still know remarkably little about other than they are particularly susceptible to human impact."
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