Cause of dolphin deaths not found

A report on the stranding of a pod of dolphins in Cornwall has found no definitive reason as to why they beached themselves.
The dolphins were found around the Percuil river in the Fal Estuary on 9 June 2008. All 26 later died. Some local people said they could have been scared by naval sonar.

A report for the Institute of Zoology said sonar activity took place "around the time" but there was no evidence it coincided with the stranding. The dolphins died when they became trapped in a number of creeks around the Percuil River in one of the UK's worst mass strandings.

They appeared to have been well fed and there were no obvious signs of disease or poisoning, post-mortem tests taken at the time showed. In its report for the Institute of Zoology, the UK Cetacean Strandings Investigation Programme said that "ultimately, a definitive cause for the MSE [mass stranding event] could not be determined". In the case of sonar use, the report said that "evidence of one or more specific naval activities that tightly coincided in time and space with the likely initial onset of the MSE were absent in all the records of naval activities released under the Freedom of Information Act".

The report also said an error of judgement by the dolphin pod could not be excluded as a factor.
It said: "An intrinsic 'error of navigation' within a social group of common dolphins, or a confluence of additional unknown (natural and/or anthropogenic) factors/sequence of events also cannot be excluded as causal factors in this MSE."

The report followed an investigation by the Department for Environment, Food and Rural Affairs (Defra).

'Most probable trigger'

However, in its own report into the incident, the Cornwall Wildlife Trust said that it believed that naval activity was considered "the most probable direct trigger". It said: "The naval exercise is the only known cause of high-intensity acoustic activities in the region of the mass stranding at that time.

"Having ruled-out other likely causes, (it) is considered the most probable direct trigger of the event, although it is impossible to reach a definite conclusion on the basis of the information received to date." The Royal Navy admitted at the time of the stranding it was carrying out training exercises with a submarine and survey ship using sonar in Falmouth Bay. But after the publications of the reports it said it did not believe the exercises were the cause because they were carried out about 60 hours before the dolphins were discovered.

http://news.bbc.co.uk:80/1/hi/england/cornwall/8102595.stm