[Shell to Sea] One possiblity that should be investigated is whether oil and gas seismic surveys had anything to do with the dolphin deaths. Last June Norwegian fisherman Bjørnar Nicolaisen came to Kilcommon and spoke on the effects that "seismic shootings" had caused to marine life in his area.  "The fish went away,  Catches went immediately 60% down...And it never came back.  It's been 3 years since the last shooting they did and it never came back... It [Seismic shooting] scares fish at least at distances of 18 nautical miles (which is about 33km),  Co-existence is impossible."  More information here: Norwegian Fisherman warns of destruction of seismic survey & Consequences of seismic surveys

At least a dozen dead dolphins were found on a number of beaches along the Achill and Erris coastline. Mystery surrounds the dolphins’ deaths, but the National Parks and Wildlife Service is to carry out postmortems on a sample of the carcasses to try to determine what could have happened. 

Local observers say three different species of dolphin – common, bottlenose and euphrosyne – were found ashore over two days on Achill beaches in the middle of last week, with the majority being the common dolphin.
Sightings of the dead dolphins were confirmed at Keem Beach, Keel Beach, Dooagh and at Dookinella, and there were also two dead dolphins found on Cross beach near Binghamstown. A statement released from the Department of Arts, Heritage and the Gaeltacht confirmed that arrangements are being made to carry out postmortems on some of the dolphins.
“Given the number of bodies reported in such a short time span and over a relatively small geographical area, the Department is making arrangements for postmortems to be carried out on a sample of carcasses this week. It will be some time before the results of these examinations will be available,” the statement read.
John O’Shea, a Irish Whale and Dolphin Group representative on Achill Island, told The Mayo News that he has never seen so many dolphins washed ashore at one time.
While strandings of live dolphins are not uncommon, these dolphins were washed ashore dead and in different stages of decomposition. There is speculation that the violent weather over the last week may be responsible, but John explained that without a biopsy confirming the deaths is difficult.
“I have never seen as many come ashore in such a small period of time. It is very unusual to see this happen, but the tide was so wild that the storm may be a factor. In 1991 there was a huge storm in Achill when a lot of fish were caught up in it and were washed dead ashore. Whether that could have affected the dolphins and they were caught by the storm I don’t know. The acid test to determine what killed them would be a biopsy,” he said.
At present, up to a dozen dolphins have been counted on the Achill beaches, but it is possible there may be more in isolated coves and inlets. Mayo County Council have started to bury some of the dolphins.
Mick O’Connell, the stranding officer with the IWDG, also told The Mayo News that they can only speculate at the moment how the dolphins died, admitting this case is a mystery.
“I have no idea how they may have died but it very unusual. While there are occasional live strandings involving dolphins where they would follow a sick dolphin into shallow water, this is different. It is very unusual to see this number of dead dolphins washed ashore in a small area. At this moment it is all pie in the sky as to how they may have died, and without a post mortem we won’t know. It could end up a mystery,” he said.