BWAS 2017: Rockall Trough Part Two - Cetaceans

Blue Whiting Acoustic Survey 2017 Week Two: Saturday 25^th to Friday 31^st March
by Sean O'Callaghan (IWDG Marine Mammal Observer)

The second week of BWAS marine mammal surveys got off to a blank start initially but the following day (Sunday) really signaled the start of a far more productive period.

Survey progress map for 31st March 2017 with thick lines show areas covered (c) Marine Institute

Not long after ascending into the crow’s nest to start the day's effort and while getting myself ready (equipping the necessary gear for the day along with applying some sun cream!) the seabird team began their observations from the bridge deck and spotted the first whales of the day which appeared initially 500m off the starboard bow, lazily surfacing, all the while moving closer to RV Celtic Explorer. Their slanted blows and boxed body shape gave them away as sperm whales and the three of them (one obviously large individual with two smaller individuals, probably juveniles) came within 100m of the vessel before diving under the bow. Moby Dick's relations up-close and personal, a great start to the day! 

Sperm whales (c) Niall T. Keogh

Sperm whales (c) Sean O'Callaghan

Sperm whale dive sequence (c) Sean O'Callaghan

An hour later, two tall blows were picked up out towards the horizon some 2.5km off the bow and when we reached the area both whales passed the vessel, decent views giving them away as fin whales on the move. The most elusive of the Sunday sightings was of an unidentified beaked whale picked up once by Aude through her binoculars while I was on a break. To round the day off we had a few common dolphins make an appearance off the port side showing no interest in the ship which has been the case for most of the survey. We had caught up with the fishing fleet on the northern side of the Porcupine Bank that day and had views of some of the large factory trawlers.

Maartje Theadora (c) Niall T. Keogh

The next batch of activity happened two days later along the shelf edge some 60km west off Mayo where more common dolphins were sighted in the morning while a group of long-finned pilot whales were recorded visually and acoustically simultaneously a kilometre and a half of the port side in the evening (really displaying how both survey methods can complement one another). While trying to get record shots of these pilot whales a distant blow from a large whale was inadvertently captured in their midst’s just as a group of offshore bottlenose dolphins powered past the starboard side to be picked up by those on watch in the bridge along with the seabird team who were up from dinner to see the pilot whales. Unfortunately these dolphins didn’t hang around and continued off in synchronised breaches which were the best that could be captured by the camera. Another day another species for the list!

Offshore bottlenose dolphins (c) Sean O'Callaghan

Wednesday was a day for housekeeping with heavy rain in the morning coupled with poor sea conditions which were unsuitable to watch or safely work in. Thursday was an unexpectedly interesting day, we had moved north into Scottish waters off the Hebrides with a species list standing at six but there was more transects to go yet. The weather had eased off and we were back on effort again. After turning onto a new transect at around 15:00, Aude started to hear a strange sounding whistle on the hydrophone, seemingly getting closer as time passed by. Continuing to watch from the crow's nest with the possibility of a new species in the area it didn’t take long to spot a large, grey, odd-shaped ship lingering on the horizon. We had heard that the survey tracklines might take us past a military exercise later in the day involving submarines, so with the navy-style appearance of the distant ship coupled with the consistency of the whistles being detected on the hydrophone, it became obvious that sonar was being used. About 30 minutes after the first ship was seen, another four appeared on the horizon to the east around the same time as the first marine mammal sighting of the day was made; a group of ten or so common dolphins moving west ahead of us at high speed! The sonar was detected for a further three hours, during which time another lone common was sighted but seemed unphased by the sound (in contrast to the previous sighting). Further sightings of common dolphins, two unidentified large whales and our first Minke whale of the survey capped off the day nicely as we continued north along the shelf edge and over shallow waters. 

Common dolphin (c) Niall T. Keogh

Navy vessels taking part in the 'Operation Joint Warrior' exercise (c) Sean O'Callaghan

Friday proved to be a fruitful day while over the deep Rockall Trough waters near the Anton Dohrn Seamount, with twenty long-finned pilot whales less than 200m off the port side just after conducting a fishing tow and before the day's watch effort began. This group of pilots engaged in some interesting behaviour such as 'spy-hopping'. Later on a lone Atlantic white-sided dolphin was seen to surface twice, giving tantalisingly brief views of the colourful side pattern but just not enough to put it down as a "definite" sighting for that species.

The day ended as the drizzle closed in from the east, with a lone large blow picked up from the crow’s nest some 3km away. Subsequent rain knocked the survey off effort for a while but as soon as it cleared we were met with the sight of a single fin whale lunging in front of the bow almost on cue in perfect sea conditions! It lunged a further three times as we steamed by, making for a nice end to the week despite heavier rain closing in!

Long-finned pilot whales 'logging' at the surface (c) Sean O'Callaghan

Long-finned pilot whale 'spy-hopping'! (c) Sean O'Callaghan

Lunge-feeding fin whale (c) Sean O'Callaghan

Fin whale lunge-feeding sequence (c) Sean O'Callaghan

Our man in the crow's nest... Sean wonders what species is next up for the marine mammal team! (c) Niall T. Keogh

COTF6 Day 5: Sunny Sightings

A perfect start to the day over the Eastern Porcupine Seabight, West of Co. Kerry (…up The Kingdom!). With a horizon clear as far as the eye could see, sun shining, cloud at a minimum, sea state of 2 and not much in the way of swell, you couldn’t ask for a better day to be out in the Atlantic in September!

Sunrise (c) Enda McKeogh

Common dolphins were as ubiquitous as they have been for the past few days, but with the sea conditions as calm as they were we could now see small groups splashing about much further towards the horizon and in a wide arc across our viewshed ahead of the ship. These progressively made their way towards the R.V. Celtic Explorer, leaping out of the water with great determination, often landing back down on their sides with a mighty splash. On closer inspection, several of the smaller, discrete groups contained calves, one of which was particularly small and provided great entertainment as it rocketed its way out of the water and towards the bow.

Common Dolphin calf (c) Enda McKeogh

Common Dolphins (c) Rossa Meade

It was a great day for long-finned pilot whale sightings, with a group of about 10 or so in our wake at first light followed up by another group of 10 later on with a small calf, which came in for a good close look at us allowing for excellent photo opportunities. A fairly abundant species with a widespread distribution in the Irish offshore territory but tied to deep water habitats and rarely seen from land so always great to encounter and see well. A firm favourite with many on board.

Long-finned Pilot Whales (c) Joanne O'Brien

Some confusingly short, bushy blows from a baleen whale which refused to show well on several occasions this afternoon had our attention focused for quite some time as it moved ahead of us on our survey transects. After much searching it eventually made a pass of the bow, surfacing on three occasions at a range of about 100m… a truly stunning view of a small, juvenile fin whale! The full suite of ID features were on offer including the white right hand side of the lower jaw, prominent ‘splashguard’ around the blowhole and whispy, grey ‘chevrons’ along the back. The small size of this animal would account for the confusing blows we saw beforehand.

Fin Whale surfacing sequence (c) Roisin Pinfield

During this time, the Irish Air Corp Maritime Squadron Casa 253 joined by Patrick Lyne and Lucy Hunt of the Irish Whale and Dolphin Group were making their approach towards the R.V. Celtic Explorer for a flyby during a routine assessment of fisheries operations in the Porcupine Seabight area. The Irish Air Corps have provided IWDG surveyors a fantastic opportunity over the years for offshore surveying by facilitating them when possible on these trips where they target recording larger species such as baleen whales and sperm whales.

Irish Air Corps Casa 253 seen from R.V. Celtic Explorer (c) Roisin Pinfield

R.V. Celtic Explorer seen from Casa 253 (c) Lucy Hunt

The juvenile fin whale had now made its way towards a second, larger individual so a decision was made to launch the IWDG RIB ‘Muc Mhara’ in order attempt a biopsy sample for genetic and stable isotope analysis. Simon and Joanne set off in the RIB accompanied by two crew members but the whales proved too quick for a safe biopsy to be taken. The sortie in the RIB did allow for some excellent photo opportunities of the R.V. Celtic Explorer from a sea level angle!

IWDG RIB Muc Mhara (c) Jason McGuirk

R.V. Celtic Explorer as seen from IWDG RIB Muc Mhara (c) Joanne O'Brien

Other marine ‘megafauna’ got a good shout in today also with a distant sighting of what was most likely a breaching bluefin tuna, fantastic views of a multiple breaching ocean sunfish and one of the undoubted highlights of the week, a leatherback turtle which was picked up just under the water’s surface as we approached it, passing along the side of the ship at no more than 30m, followed by two superb views of it surfacing, head and ridged carapace (shell) right out the water! Leatherback turtles regularly occur in Irish waters with a widespread distribution right across the Atlantic frontier and even up into the Irish Sea. Views as good as the one we had today are hard to come by however as they often only spend brief periods at the surface so finding them in the first place is hardly an exact science.

Leatherback Turtle (c) William Hunt

Leatherback Turtle (c) William Hunt

The seabird team had barely got started with their morning’s census (some 50 nautical miles West-Southwest of the Skellig islands) when a pair of shearwaters rose up ahead of the R.V. Celtic Explorer, one a Manx shearwater, the other a much smaller and rarer Barolo shearwater! The two birds continued ahead of the ship, moving away in a Northerly direction, heading off to our port side, allowing for a perfect comparison of both plumage features and flight style between these two somewhat similar looking species (at least according to the field guides, seeing them together in ‘the field’ however is a different story… like chalk and cheese!). Barolo shearwaters breed across the Macaronesian archipelago, specifically the Azores, Madeira and the Canaries. They are a rare, infrequently recorded species in Irish waters, most often from West coast headlands in late Summer or Autumn, with just 22 records documented up to the end of 2012 (per the Irish Rare Bird Committee reports). A most unexpected and welcome sighting, certainly one of the many avian highlights of the week.

New bird species added to the trip list today included a couple of grey phalaropes, a handful of guillemots and a migrant swift flying around the ship. Seabird numbers were generally low throughout the day, a few diving gannets and milling fulmars indicating some feeding opportunities were on the cards in this area. Two great shearwaters, 10 sooty shearwaters, 9 European storm-petrels and 9 great skuas were the best of the rest. One of the two kestrels which came aboard last night was seen again this morning, leaving the ship and heading off on its merry way. A few new meadow pipits joined us over night also, one of which ended up inside the bridge and took its place in the captain’s chair while everyone was off watching the match. Good to know somebody was steering us in the right direction!

Captain M. Pipit (c) Niall Keogh

Captain M. Pipit (c) Jason McGuirk

Tonight we will zig-zag North West along the Eastern Porcupine Seabight and cross North East over the Hovland Mound SAC once more in the morning while we make our way back towards Galway. The lads on the night time acoustic monitoring shift will continue in their endeavour to decipher what whale and dolphin calls they hear coming out of the depths. Enda reports that after some analysis, a series of clicks they picked up last night almost certainly came from a species of beaked whale, a group of enigmatic, poorly understood and rarely seen cetaceans which we know occur with some frequency in the Irish offshore territory but to date have given us the slip on many occasions, often showing only briefly when they do. Tantalising stuff, but it certainly keeps us motivated!

Sunny surveyors (c) Niall Keogh

COTF4 Day 4: Return to Form

Expectations were high as we skirted along the edge of the Porcupine Seabight shelf, a habitat far more productive for feeding cetaceans & seabirds compared to the ‘abysmal’ plains we were over for the past few days.

Conditions this morning were a lot like yesterday with favourable swell, sea state & wind in comparison to recent days but with a hint of the dreaded sea fog lingering. This cleared up after an hour or so however and with that, the birds started tipping by nicely and by mid morning we had our first cetacean sighting.

Kittiwakes were the order of the day for the seabird team, with double figure flocks loafing around the R.V. Celtic Explorer for much of the morning, no doubt thinking she was a trawler. All this activity drew in some gannets (our first in days), small numbers of great skuas and plenty of fulmars. We then sailed into a feeding flock which produced added bonuses in the form of a puffin and a manx shearwaterwhich was a new species for the survey list.

 Perfect 'as you see in the field' flight pic of a winter plumaged puffin (c) Alex Borawska

A young kittiwake with fulmars behind (c) Alex Borawska

Soon to follow was a sighting of at least two bottlenose dolphins off the starboard side. At last! Our target species for the trip. They moved on quickly however, but not before engaging in some belly rolls & tail fluking/slapping.

Not long after, the PAM team picked up some strange clicks on the hydrophone which could possibly have been a species of beaked whale. A little understood group which have been seen and heard on previous Cetaceans on the Frontier surveys. Tantalising! So to was a distant blow from a large whale species. 

Things really kicked off in the afternoon as we travelled right over the shelf from a water depth of 1000m to 200m. By this stage the wind was also blowing a good force 7 north west. Kittiwake numbers started to fluctuate dramatically, with flocks of up to 185 trailing us at times, again interspersed with more gannets, fulmars, great skuas, another puffin and most surprisingly a 1^st-winter glaucous gull (scarce winter visitor from the Arctic). We then came upon an active trawler and between its own entourage and those tagging along with the R.V. Celtic Explorer, a vast cloud of seabirds formed, comprising of 600+ kittiwakes, 100+ fulmars and 50+ gannets. Up to 4 ‘blue’ fulmars and a single great black-backed gull added some variety to the frenzy, all the while our friendly neighbourhood glaucous gull was still drifting alongside.

 1st-winter glaucous gull (c) Alex Borawska

A gnarly old great skua (c) Alex Borawska

A 'blue' fulmar, the darker, Arctic breeding counterpart (c) Niall Keogh

                              Kittiwakes en masse! (c) Alex Borawska

The best was most certainly saved for last. The cetacean team picked up an active group of breaching dolphins dead ahead of the bow which were quickly identified as more bottlenose! About 50 were present in total, leaping right out of the water and travelling at great speed past our port side. Some quick manoeuvring by the ships crew allowed for photo-ID but the dolphins obviously had other things on their mind and after several minutes, they slipped away with little effort.

An excellent sighting of an enigmatic group of animals.

Our Chief Scientist, Conor Ryan explains…

”We encountered about 50 bottlenose dolphins 58 miles west of Slea Head this afternoon, about an hour before darkness and in the teeth of a gale. It was in this same area, just on the edge of the continental shelf, that I witnessed my first 'offshore' bottlenose dolphins, in summer 2008. It seems that as we have come to expect, they did not approach the ship and we found it difficult to approach or track them. This strong avoidance of vessels appears to be a behavioural trait of offshores, unlike their inshore counterparts who cannot resist a good bow wave! Although we have yet to carry out a detailed analysis, the offshore bottlenose dolphins appear to be darker in colour and may be slightly smaller than the 'inshores'. We hope that with more genetic, morphometric and behavioural data, we can start to understand just how different these dolphins are to the coastal bottlenose dolphins.”

Offshore bottlenose dolphins (c) Simon Berrow

Offshore bottlenose dolphin...nicks along the dorsal fin useful for photo ID (c) Alex Borawska

Offshore bottlenose dolphin...Some individuals are strikingly dark with a well defined pale belly (c) Emilia Chorazyczewska