Harbour porpoise surveying - Celtic Mist at the Tuns Bank

3rd Jun 2016

The 3rd leg of the Celtic Mist’s grand tour was taking it from Killybegs to Ballycastle providing an opportunity to look at cetacean activity over the Tuns Bank. This area has been on local (northern) IWDG cetacean watchers ‘to do’ list for some time.

There is evidence, gathered some time ago as part of a preliminary environmental assessment for an offshore windfarm proposal (that, to-date, has not been progressed), that these sand floored shallows are a regular/notable birthing ground used by our smallest cetacean, the harbour porpoise. More recently, land-based sightings have confirmed the presence of mother/small calf pairs in the area.

So last Wednesday saw me scouring the inshore waters by telescope to see if any porpoise activity could be detected. While I was covering the cliffs and dunes between Castlerock and Magilligan Point (along the north Derry coastline), Celtic Mist was making its way to our rendezvous point at Greencastle, Co Donegal. Sea conditions were not ideal for either party, slowing the progress of Celtic Mist and making porpoise spotting difficult. While no sightings were made (Celtic Mist on the other hand encountered a minke whale) there was plenty of seabird foraging activity to keep hope alive for the following day.

Celtic Mist rounding Inishowen Head

Thursday morning arrived overcast and calm – perfect for cetacean surveying with no glare and little in the way of waves. I did a land based search over the Tuns Bank from Inishowen Head north of Greencastle, before breakfast with a few porpoises noted and, importantly, 2 mother-small calf pairs. Just the incentive we needed. Loads of guillemots, razorbills, gannets, cormorant, shags and manx shearwater were also present, together with a few summer plumaged Great Northern Diver.

Tuns Bank area

Joined by Cathy Hinds (Northern Ireland IWDG Officer) we left Greencastle immediately encountering a porpoise near the harbour – great start. A run up the channel between Inishowen and the Tuns Bank disappointingly yielded nothing – not even the seabirds I saw in the morning. We then followed an easterly route towards the mouth of the River Bann, again with no sightings. And we couldn’t even blame the sea conditions as the weather was near-perfect. Finally on our homeward run we encountered a total of 5 porpoises, along the edge of the Tuns shallows, but careful scrutiny showed that no calves were present. Back to Greencastle, Cathy and I left Celtic Mist to prepare for their run to Rathlin, where I will meet up with them again on Saturday. Cathy is joining the ship again on Monday for the run back to Dublin.

Celtic Mist approaching Greencastle with Magillan Point and Binevenagh in the background

So what have we learnt? Well the trip confirms that the Tuns Bank area appears to be of significance for harbour porpoise – all sightings through the day were centred on the Tuns Bank or its immediate area. Confirmation again of porpoise calves underlines the need for further investigation.

What comes next? Inevitably there is a need for more survey data falling into 2 categories. Firstly I would love it if some volunteers from the Inishowen area could undertake targeted land-based surveys of the Tuns Bank in good sea conditions. There are excellent vantage points to do this from and even a few hours of coverage per month would increase our knowledge enormously of this potentially important area. Please contact IWDG if you are interested.

Secondly further boat-based surveys are needed through the birthing season (approximately April – August) and ideally year-round to understand better how harbour porpoises are using the area and to better understand why the area is of such significance.

Many thanks to Celtic Mist skipper Garry Davies for having us on-board and coordinating the survey and to the IWDG stalwarts supporting (and working their passage) on this leg of the Celtic mists tour of Irelands wonderful coastline

Ian Enlander, IWDG

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