Large increase in strandings of common dolphin UPDATE

18th Apr 2011 Update 18 April 2011

The large increase in strandings of common dolphins, noted in January and February, has continued into March and April.

The total number of common dolphin strandings in 2011 is now 26. Three of these were live- stranded, two in Galway and one in Cork, with one successfully re-floated. There does not seem to be a difference in gender of the stranded animals, as half of them were males and the other half females, although the gender of six dolphins stranded was unknown.

Looking at previous years, there has been a big increase in strandings of common dolphin. With a total of three strandings in the first four months of 2010, the increase in 2011 was almost 88%. The increase with 2009 and 2008 was 73%. In recent years the highest figures for common dolphin strandings in these months was in 2007 with a total of 19 common dolphin records. Comparing 2011 with 2007, the increase was still 27%.

There has been a big increase in strandings in February, with a total number of 15 in that month, compared with 1-4 in previous years. This has been the highest monthly total of common dolphins strandings since recording began.

The strandings have occurred mostly on the south and west coast from Waterford to Donegal, with the exception of one common dolphin stranded in Killiney bay, Dublin.

Most strandings were in Counties Cork and Waterford with seven strandings each. None of the animals were fresh enough to support a post-mortem examination, so the cause of death of these animals in unknown.

Looking at other species, there hasn't been a much of a difference with previous years, except for a small change in the number of long-finned pilot whale Globicephala melas strandings. There were no strandings of this species in January to April 2010, but six so far this year. The first four months of 2007 counted three strandings and the first four months of 2009 counted two strandings. Only 2008 had more strandings of this species in January – April, namely 13 individuals. Although this difference is not as extreme as in the common dolphin case, strandings may be elevated.

Many thanks to all the people who reported strandings.

Lonneke Ijsseldijk

ERASMUS student with IWDG

9 March 2011

Reported strandings of common dolphin in Ireland during January and February 2011 are significantly higher than in previous years. So far, IWDG have received reports of 18 strandings of 19 common dolphins over these two months, accounting for a remarkable 60% of total stranding incidents reported. The majority of strandings have occurred on the south coast in counties Cork, Waterford and Wexford but they extend as far as Mayo and Donegal.

In order to put these figures into some perspective, two common dolphin strandings were recorded in January/February 2010 accounting for 16.7% of total strandings and in the same period in 2009 three strandings accounted for 12%.

In recent years, the highest figures for common dolphin strandings during these two months had been in 2007 when 10 strandings of 11 animals were recorded, accounting for 37% of total cetacean strandings.

Some dolphins were in poor condition and must have been dead for a number of days/weeks, while two were lived stranded together in Co Galway. Many were in very good condition.

It is not known what may have caused this increase in strandings.

Mick O'Connell

IWDG Stranding Co-ordinator

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