Friday, 25 January 2013

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 1st-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

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