Mass stranding of common dolphins in Cornwall

10 June 2008

On Monday 9th June, 26 common dolphins were stranded and then perished near St Mawes in Cornwall. Cornwall Wildlife Trust has been working closely with the Institute of Zoology and the Veterinary Laboratories Agency in Truro to try to find the answer to the question on everybody’s lips, "why did this happen and can we do anything to prevent this in the future?"

Reports started coming into the Trust’s Strandings Hotline and to British Divers Marine Life Rescue (BDMLR) early on Monday morning and the extent of the incident quickly became apparent. As the Trust’s strandings volunteers worked with others to locate and remove the dead dolphins, BDMLR responded extremely quickly to the live strandings and successfully re-floated seven animals which appeared to be doing well. The response to this incident was extremely good with many individuals and numerous organisations dedicating long hours at short notice to assist in this emergency.

In addition to the stranded animals on the shoreline a discovery was also made of a group of common dolphins in the Falmouth harbour area near the Maritime Museum. These individuals were showing signs of normal behaviour, but worries were raised that they may head up the creeks and become stranded. BDMLR, with the assistance of the Harbour Master and several members of the public, assisted in corralling this group into deeper water. So far there have been no further reports of additional strandings and everybody involved is hopeful that this will be the end of a tragic event.

The scale of this mass stranding is unprecedented in Cornwall and has been a shock to everybody. Work is progressing quickly to find a reason why this happened. There are several possibilities, but none of which have yet been confirmed.

This season the plankton bloom has been relatively late and may have put increased pressure on all marine life to find food. This may have caused these dolphins to head up stream to warmer waters where phytoplankton blooms were occurring earlier to feed on fish species feeding on the algae. There have also been instances in the past in different countries of toxic algal blooms causing fatalities in dolphin populations. This occurs because the dolphins are the apex predator and accumulate toxins as they feed on smaller fish. Another possibility which has been seen in other regions of the world is increased naval activity and the use of very powerful sonar devices.

Tom Hardy, Marine Conservation Officer for Cornwall Wildlife Trust said, "All the animals recovered to date have been adolescents and appear to be in very good condition with no obvious signs of malnourishment or physical injuries."

Tom continued, "Of the 26 dead animals recovered 15 are undergoing post-mortem examination by the Institute of Zoology on site today. Eight additional bodies were taken for autopsy, five of which were adolescents and three of which were lactating females - unfortunately the juveniles have not been sighted."

The Trust could not have responded yesterday without funding from our members or without the help from our many dedicated marine volunteers. If you would like to make a donation to Cornwall Wildlife Trust’s marine work, please send a cheque made payable to Cornwall Wildlife Trust to 'Marine Donations', Five Acres, Allet, Truro, Cornwall, TR4 9DJ.

Zoological Society of London press statement about post-mortems:

ZSLcornwallmassstrandingstate.pdf

25/06/08 - Latest statement to us from the ZSL:

"All 26 common dolphins in the mass stranding event of 9th June 2008 have now been examined (dissected) and a range of tissue samples have been generated. These tissue samples are now in the process of being analysed for a range of potential causes including morbilliviruses, Brucella, etc. Defra have already allocated some emergency funding to help with this investigation but, at this stage, we are not sure how long it will take to complete the investigation and publish the findings."

Paul D. Jepson BVMS PhD MRCVS
Senior Research Fellow
Graduate Tutor
Institute of Zoology
Zoological Society of London