Irish Risso's Dolphins Matched to the Isle of Man?

31st Jul 2009 The IWDG has recently expanded it's photo ID catalogue to include Risso's dolphins. These are an enigmatic pelagic dolphin species that appear to move inshore during the summer months. Their global population status remains unknown and they are thus a species of high conservational concern. A quick search of our sightings database will reveal a marked seasonal increase of sightings of this species along the east and south coasts between May until August each year. Offshore islands appear to be favoured by Risso's dolphins, particularly The Blaskets, Saltee, Cape Clear and Dursey Islands. The cause of this annual inshore movement for a deepwater squid-eating species remains unknown.

Not long after the inception of our online Risso's dolphin catalogue, colleagues on the Isle of Man contacted us about a possible match. We have sent a hard copy of our catalogue to Tom Felce and John Glapin of the Manx Whale and Dolphin Watch with higher resolution images in order to confirm this match. We will keep our readers up to date with any progress on this.

Photo identification is proving vital in our understanding of many cetacean species in Irish waters. For example, video footage and images from a recent and unprecedented mass stranding of 17 bottlenose dolphins in Tralee Bay confirmed that these were not Shannon Estuary dolphins. This was welcome news, as 17 individuals would represent around 7% of the Shannon putative resident population. We would like to thank everyone who contributed to the catalogue so far and will gratefully receive any more high quality images of Risso's dolphins in Irish waters.

Conor Ryan & Vanessa Klotzer


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