May 2012 Cetacean & Basking shark Summary

1st Jun 2012

Although not a record month of May, it had in terms of volume of sighting reports, a nice geographic spread along with a good species mix. The IWDG received, validated and processed 144 sighting records of 8 species. Cetacean activity was reported each day of the month. This compares with 82 records for the same period in 2011. 89% of all sightings were validated to species level, the remaining 11% were allocated to a "non species" category.

Downgraded sightings should not be looked on as being somehow inferior, they simply reflect the fact that there was insufficient diagnostic information or photographic evidence to confirm species identification. Such records are still important in helping us build up that "big picture" of how species are using our waters. People might sometimes feel that validation is a one-way process, by which sightings are only downgraded, but for every downgrade there are generally a similar number of upgrades. For instance, where you the recorder are not sure of what it is you've seen, but with the information you've provided, we can be reasonably confident on species ID.

During May there were as always some nice surprises. For instance, the harbour porpoise was relegated to 2nd place in rankings (19%), with the bottlenose dolphin taking 1st place as the most regularly reported species (30%). Bottlenose dolphins were recorded in ten coastal counties. The Killiney Bay group in Co. Dublin which were recorded on 9 days between Bray and Dalkey, which is interesting as people may think they are recorded every day in Killiney Bay which is simply not the case. They have recently been recorded as far north as Skerries. The event which stood out was the sighting of a group of up to 6 bottlenose dolphins in Bellacragher Bay, Near Mulranny, Co. Mayo between 1st and 7th May (photo below). This event unfortunatly ended in the death of at least one of this group.

The pelagic Common dolphin ranked in joint 3rd place with 13.3% of sightings, and surprisingly some of these were of very large aggregations, with between 250-300+ in Dingle Bay on 12th and 20th May reported by Nick Massett. These large groups were not restricted to inshore waters as Tony Murray, NPWS observed upwards of 250 in waters offshore Co. Wexford on 27th May while returning on a ferry from France.

Sharing joint 3rd place was our smallest and most commonly seen rorqual, the minke whale, with 19 records from 7 coastal counties. The standout records here were two singles from Ballyhornan and Bloody Bridge Co. Down during monthly IWDG effort land-based watches by David Williams. After years of reporting local harbour porpoise action along the Down coast, it is fantastic that David is now starting to report minke whales inshore along this stretch of the North Irish Sea. Proof, not that its needed, that those who put in the Cliff time will sooner or later start to record larger species along their patches.

The above minke whale image shows just how close this species can come to vessels, as it circled a fishing vessel on several occasions. It was the latest in a run of great sightings in the waters adjacent to the Saltee Islands from Mssrs. Hinchy & Devereaux, which also include Risso's dolphins and "large whales", likely to have been fin whales.

Basking sharks were also evident during the first two weeks in May with 11 sightings, but a decline in sightings in the past two weeks suggest that we may have seen the peak of sightings of this species in April which had 47 sightings. To date in 2012 we have received 79 basking shark sightings from around our coast, which compares with 105 records for the same period in 2011. But it is a little too early to write off the 2012 basking shark season, so watch this space. It only takes a little sunny weather to bring that plankton back to the surface, and these grazers are sure to follow.

The other species recorded in May were Risso's dolphins and our largest dolphin species, the Killer whale for which 3 sightings were made off Counties Kerry (1), Mayo (1) and in the North Channel (4). One humpback sighting south of Clonakilty Bay on 16th May by West Cork whale watch operator Colin Barnes, brings the species tally to 8. Whether this was a new individual or one of the two animals HBIRL18 & 20 recorded in April in the same area is uncertain.

A huge thanks to the 13 whale enthusiasts who joined IWDG last weekend for the 1st of our summer series of whale watching weekend courses on Cape Clear Island. Alas, the weather mitigated against sightings with gale force 8 easterly winds and when these abated they were replaced by sea fog, limiting visibility to a few meagre metres. So predictably we struggled to find cetaceans, other than a single harbour porpoise on the return ferry to Baltimore on May 27th. Cruelly, not one but 2 minke whales were recorded on the afternoon the course ended; one to the west of Cape Clear in Roaringwater Bay and the 2nd south of Gascanane Sound. This serves as a reminder that cetaceans don't disappear during poor weather, we just struggle to find them.

These weekends are not so much about showing people cetaceans, but about giving people the confidence to find, identify and record them and we hope that the course participants feel a little more confident in reporting cetacean sightings to IWDG in the years ahead and will become involved in the group as active members. There are about 6 places remaining on the July 20-22nd Cape course, so please drop us a line on padraig.whooley@iwdg.ie, if you'd be interested in finding out more about these weekends.

We aim to do a monthly sightings summary over the summer period to keep you informed as to what is being seen around our coast. But please note that most sightings are validated and made available for online interrogation on this site in real time or within the same 24 Hrs. So you can keep right up to date on the latest developments, or check historic records in your locality. This is a uniquely powerful research tool which we make available to you at no cost. We hope that those of you who use it regularly will consider taking out IWDG membership that will help us continue to provide this service in future.

We are looking forward to another good summer of activity, and please do report sightings on www.iwdg.ie where it will take a few minutes to complete an online sighting of any cetacean or basking shark. Thanks as always for taking the time to report your observations to IWDG.

By Padraig Whooley
IWDG Sightings Co-ordinator