The mystery of the fin whale stranding explained

Photo credit: Chris Bishop

Photo credit: Chris Bishop

Last Thursday, a juvenile, female, fin whale washed up on Holkham beach in Norfolk. This makes it the latest in a series of unusual whale strandings along this stretch of the coast.

Fin whales are rarely seen in the North Sea with the majority of coastal UK sightings coming from the Shetland Islands, Outer Hebrides, south west Ireland and in the Celtic Sea between southern Ireland, west Wales and south west England.

Despite the event being described as unusual, it is not an isolated incident. In fact it is the tenth reported stranding on the southern North Sea facing coastline of the UK since 1990.

A post-mortem was carried out by the Cetacean Strandings Investigation Programme (CSIP) on Friday afternoon. The whale measured approximately 13 metres in length and was in very poor nutritional condition at the time of death. Parts of the spine were seen protruding along the posterior of the body and the body shape had a distinct curvature, bending by 30-40 degrees at the tailstock. In close association there was also a dorsal “hump” and upon dissection the vertebra were found to be misaligned. The preliminary cause of death was pinpointed to starvation, consequential to spinal abnormality.

However, CSIP were unable to access the left side of the whale’s body and so the question of whether there may have been any traumatic injuries to this aspect of the whale remained unanswered. This was until a local photographer came forward with a photograph she managed to capture before the team arrived which revealed a deep laceration on the left side of the body.

The cause of the lesion remains unknown, but is speculated to have arisen from a past traumatic event which injured, but did not kill the whale. The event caused damage and deformation to the vertebra and musculature around this region. It is thought that the spinal injury limited the extent of movement in the caudal peduncle (where the tail fluke attaches to the body) which lead to the progressive wasting of the musculature in this area. The injury impaired the whale’s ability to dive and feed which subsequently lead to starvation and the ultimate live stranding before death.

CSIP have since updated the provisional cause of death to starvation, consequential to spinal abnormality from a possible ship-strike. They are yet to carry out further analyses to confirm the identity of the traumatic event. Currently, a ship-strike is not being ruled out although the fatality could have easily been caused by other traumas.

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Lucy Grable

Lucy Grable

MSc Species Identification and Survey Skills student at Reading Uni | BSc Marine Zoology | Website Editor MARINElife | Zanzibar humpback whale researcher|Marine wildlife enthusiast

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