IWDG team join the Blue Whiting Acoustic Survey - Marine Mammal Report

8th Apr 2017

Updated 9 April 2017

This year’s blue whiting acoustic survey began far off the Southwest coast on the Porcupine Bank. To get there we swapped the shelter of Galway Bay for the Atlantics growing swell, giving us a taste of the less than desirable forecast on the way. It took a day to reach the surveys first transect line but in that time the storm’s swell had risen to sickening levels (literally). During this transition period the equipment was readied for what was to come on a day where if you weren’t sliding across rooms by chair, you were walking against a steep gradient or pacing yourself down when it switched the other way around. There was a technical issue at first but with advice from Dr Joanne O’Brien we were ready for the start of the survey the next day.

Given the area the acoustic survey was scheduled to cover some attractive species had the potential to be picked up, namely sperm whales around the deep waters of the Rockall Through and the North Atlantic specialist’s the white-beaked dolphin and Atlantic white-sided dolphin. These three species were high on my wish list while long-finned pilot whales and sperm whales were the targets for Aude, the surveys PAM (passive acoustic monitoring) operator.

Day one saw us frequent the ships sheltered bridge to see what may be present but it was more of a water watching experience as hostile hills capped in white rolled in from the horizon while the occasional snow flurry or hail shower struck the ship, only the birds were visible that day. After a blank start, day two produced the first blubber in the form of common dolphins appearing at the bow and vanishing off the port side into the still strong swell.

It often felt as though each good day with sightings was being counteracted by a dud day while on effort, sometimes the highs were the height of a stormy swell but other times you may as well have been out on a lake.

The first big day for activity was also the first day upstairs in the crow’s nest, not long after settling in to the ships modern masthead two bushy diagonal blows puffed near the horizon instantly revealing the presence of sperm whales, top of my three target species list for this cruise, alas they didn’t make much of themselves in passing so all eyes were open for what else was lurking in the deep. Another deep diver appeared later that morning but in a lot closer as a small group of pilot whales, they too didn’t hang around but that was fine as they had been logged downstairs.

The 26th March has become one of my highlight days, whale wise in Irish waters. Three sperm whales were picked up quiet close to the bow and approaching slowly as we steamed forwards. The whales certainly lived up to their defining characteristics in the field guides with crinkled skin, broadly boxed off heads, an snubbed dorsal fin and knuckled tail stock tapered off to a triangular tail fluke. Their blows seemed to barely break the surface as they edged over to us. Just when a collision seemed imminent, the biggest of the bunch decided to go deep and dived almost to the point of fluking but just held off beneath the water’s surface where the fluke was revealed to be missing its corner chunks at each tip. Moments later the other two whales followed suit as we motored on, all those within earshot of the walkie-talkie in the dry lab were treated with this spectacle from the bridge deck, what better way to start a morning?. Fin whales made themselves known along with a beaked whale picked up by Aude later that day but leviathan’s of a manmade verity were hard to avoid when we caught up to the blue whiting fishing fleet, particularly the two factory freezer trawlers in the vicinity of the Explorer.


Sperm whale forward blow and a trio of Sperm whales

A brief sighting of some boisterous offshore bottlenose dolphins breaching off the starboard side was the last surveying high point before another stormy day occurred which was very much spent indoors pawing around the ship all the while trying to maintain some bit of balance/composure as the boat bounced about. Due to time it took to complete a series of short transects and linking intertransect lines on the Porcupine Bank, the initial plan to head out over the Rockall Bank and Plateau was scrapped to catch up with the rest of the survey vessel that had progressed more quickly northwards. Instead the Dutch ship MV Tridens was gifted this part of the North East Atlantic to investigate.


Bottlenose dolphins fleeing the ship of fthe Porcupine

Moving North into Scottish waters, the hydrophone became overrun for a time by sonar sounds emanating from five NATO warships and an unknown number of submarines as part of the annual Joint Warrior Military Exercise. Sightings were still made, initially of common dolphins gunning it in the opposite direction of these ships but later another marine mammal joined the surveys tally, a lone minke whale.


NATO vessel on Military exercise                                                                                   Large pelagic  fishing  trawler Theodore

The Northern half of the survey produced more common dolphins and pilot whales along with a single Atlantic white-sided dolphin that just revealed enough detail to call it as such before moving out of sight. The second highlight of the trip was undoubtedly during the rain where a single fin whale inadvertently put on a show in the serene stillness of a sea state one. Having chanced waiting out a band of dense yet light rain which reduced visibility to unworkable levels after seeing a large whale blow before the rain caught us, a bit of patience really paid off! When in the clear a single fin whale was seen speeding up, turning on its right side and unfurling its vast throat and associated pleats before snapping its lower jaw shut, spewing seawater out like steam and then righting itself for a bit of digestion, lunge feeding from start to finish not once but four time as we sauntered onwards! It was the first time I’ve properly seen this behaviour play out fully and this particular Scottish whale left nothing to the imagination.


Lunge feeding fin  whales

A third, far larger storm caught up to the Explorer as we began April, making it officially too poor to watch not long after it got us but Niall still managed to see two groups of pilot whales close in, breaking through the swell. The ships main goal when the storm approached was to finish the last transect as quickly as possible to head south for the shelter of the Minch’s in Scotland where the Outer Hebrides would bear the brunt of the Atlantic. While sheltered, a considerable swell still managed to move up the Minch buffeting the bow but not as badly as it would have been in open water. Three killer whales had been sighted on the Atlantic side of the Minch the previous day while Risso’s were in the East side of the Minch a few days beforehand, but unfortunately we had no luck on that front. The proceeding day was spent moving south to Donegal where the swell hit once again making moving around the ship a procedure in timing and choosing a suitable hand hold. During this time the surveys paperwork was drawn up to see how we did. The weather had died down to ideal levels by the time the Explorer returned to Galway Bay where we would wait for the tide and pilot to return to the docks more stable substrate. Just before passing through the lock gates and after nudging by Nimmo’s Pier we were met with our final sighting of the trip, the pier’s resident bottlenose dolphin. In the glassy water where Galway Bay’s high tide intermingled with the River Corrib’s outflow, the dolphin surfaced slowly taking shallow dives a number of times almost remaining stationary just off the pier, an inshore bottlenose dolphin to complement the offshore individuals we had nine days earlier!


Scotland !!

With twenty sightings of 70 individuals while on effort comprising of 8 (six of which were in Irish waters) cetacean species we did good considering the elemental restraints at times and apparent lack of life on good days.

Aude got her pilot and sperm whales with the added bonus of a beaked whale on top of various acoustic detections throughout the survey while I got two of the three target species on the wish list which was great, it’ll give me an excuse to try again some other time.

Sean O'Callaghan

IWDG cetacean Surveyor

All images by Sean O'Callaghan


Updated 3 April 2017

See report of last week on


due into Galway at the end of the week after 3 tough weeks I'd say .....................

Updated 27 March 2017

See report of first week on


Follow the adventures of the IWDG research team on RV Celtic Explorer during this year's Blue Whiting Acoustic Survey. The IWDG team of Sean O'Callaghan, Aude Benhemma-Le Gall and Carlota Vialcho Miranda join BirdWatch Ireland's Niall Keogh to conduct cetacean and seabird surveys, including towed passive acoustic monitoring. All are also students at the Galway-Mayo Institute of Technology registered for either a PhD (Niall), MSc (Aude and Carlota) or under-graduate degree (Sean).

This is the ninth year the IWDG have collected sightings data on this annual survey. We started in 2004 with Dave Wall and have also been out in 2008 and annually since 2011. Birdwatch Ireland started collecting concurrent seabird data since 2012. Since 2014 we have also been using a towed hydrophone to collect PAM data. These datasets become increasingly more valuable with each additional year as the distribution of fish marks and density are also collected as well as environmental data, allowing us to look at long-term changes in populations and also asses the interactions with fisheries. 

A range of species are typically recorded including long-finned pilot whales, common, striped and bottlenose dolphins and occasionally white-beaked dolphins. Large baleen whale sightings are rare but sperm whales are regularly seen and frequently heard on the hydrophone. 

 Long-finned pilot whales photo: Niall Keogh. 

Follw the team on http://cetaceansonthefrontier.blogspot.ie/2017/03/blue-whiting-acoustic-survey-bwas-2017.html


Aud, Niall, Carlota and Sean, smiling at the start of the survey. Will they be smiling at the end !!


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