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Static Acoustic Monitoring Deployment and Cetacean and Bird Survey of the Porcupine

Cruise Report on CV14020 Deployment of Passive Acoustic

Monitoring Equipment in the Porcupine Basin and adjacent Shelf

Edge and Concurrent Cetacean, Seabird and Passive Acoustic

Monitoring Survey – May 17 to 21, 2014

Bermuda Petrel (Cahow), Porcupine Bank, 19 May 2014 © Ryan Wilson-Parr

May, 2014

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Suggested citation:

Berrow, S. McKeogh, E. Keogh, N. Wilson-Parr, R. Russell, C. Meade, R. 2014 Cruise Report on

CV14020 Deployment of Passive Acoustic Monitoring Equipment in the Porcupine Basin and

adjacent Shelf Edge and Concurrent Cetacean, Seabird and Passive Acoustic Monitoring

Survey, Galway-Mayo Institute of Technology Document CV14020 Cruise Report by GMIT for

Woodside Energy (Ireland) Pty Ltd.

Simon Berrow1,2, Enda McKeogh1, Niall Keogh3, Ryan Wilson-Parr4,

Clodagh Russell1 and Rossa Meade1

Cetacean Survey Team – SB, EMcK, RM, CR Bird Survey Team – NK, RW-P

Passive Acoustic Monitoring – SB, EMcK Visual Cetacean Surveys – RM, CR

1 Irish Whale and Dolphin Group, Merchants Quay, Kilrush, Co Clare

2 Marine and Freshwater Research Centre, Galway-Mayo Institute of Technology,

Dublin Road, Galway

3 BirdWatch Ireland, Unit 20, Block D, Bullford Business Campus, Kilcoole, Co. Wicklow

4 Ecologists Ireland Consultants Ltd, 78 Gleann Alainn, Tullyallen, Drogheda, Co. Louth

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INTRODUCTION

The waters of Ireland’s Exclusive Economic Zone (EEZ) are thought to represent some of the most

important cetacean (whales, dolphins and porpoise) habitats in Europe. To date, 24 species of

cetacean have been recorded, with seven of these having been confirmed as calving within the Irish

EEZ (Berrow 2001) and a number of other species are possibly calving (e.g. minke whale and

northern bottlenose whale). In recognition of their importance for cetaceans, the Irish government

declared all Irish waters (within the EEZ) to be a whale and dolphin sanctuary in 1991 (Rogan and

Berrow 1995) and under the EU Habitats Directive all species of cetacean are entitled to strict

protection including of their habitat. Despite this recognition, information on the distribution and

relative abundance of cetaceans within the Irish EEZ, especially in offshore waters, is still limited

(Wall et al. 2006). The Irish Whale and Dolphin Group (IWDG) have been collecting data on the

distribution and relative abundance of cetaceans in Irish waters (including Northern Ireland) since

1991. The IWDG casual and constant effort sightings schemes record data mainly from land-based

sightings and surveys (Berrow et al. 2010) with a strong emphasis on “citizen science”. Dedicated

offshore surveys in Ireland have been relatively limited given the large costs involved. In 1994 the

Celtic Sea was surveyed as part of the Small Cetacean Abundance in the North and Baltic Sea

(SCANS) international survey targeting the harbour porpoise (Hammond et al. 2002). A repeat of this

survey (SCANS II) which included all continental shelf waters was carried out in July 2005 (Hammond

et al. 2013). A similar dedicated survey of all waters beyond the continental shelf was carried out in

July 2007 but excluded the porcupine Seabight (Hammond et al. 2009). These surveys generated

density and abundance estimates for the most frequently recorded species. The first offshore atlas

of cetaceans and seabirds were created between 1999 and 2001 as part of the Petroleum

Infrastructure Programme funded projects, largely from platforms of opportunity. O’Cadhla et al

(2004) presented 772 cetacean sighting records from 442 survey days at sea and showed the

Porcupine Bight was important for pelagic dolphins and fin and other baleen whales. An atlas of

cetaceans in UK and Irish waters was published by Reid et al. (2003) using a combination of datasets.

This suggested the porcupine bight was important for bottlenose dolphins and long-finned pilot

whales.

Since 2001 the IWDG have established an offshore recording scheme through conducting cetacean

surveys onboard ships of opportunity including commercial ferries, research and naval service

vessels. IWDG also utilise the Maritime Squadron Air Corps Casa 252 aircraft as platforms for

offshore surveys (Wall et al. 2013) and since 2008 have carried out a number of dedicated shelf edge

cruises under the Cetaceans on the Frontier programme. These data have recently been used to

create an updated offshore atlas of the distribution and relative abundance of cetaceans within the

Irish EEZ (Wall et al. 2013). IWDG continue to exploit opportunities to carry out surveys in Ireland’s

offshore environment to fill in gaps in coverage and provide data useful for monitoring changes in

distribution and abundance.

Acoustic monitoring has been carried out in Irish waters for a number of years (O’Brien et al. 2009).

Most has been carried out in inshore waters but two large scale offshore acoustic surveys using

towed hydrophones have been undertaken over the past 10 years (de Soto et al. 2004; O’Brien et al.

2013). Most of this effort was over deep-water off the northwest and along the shelf edge with little

effort in the Porcupine Bight or slopes. Static acoustic monitoring (SAM) in the offshore environment

is much more recent. Extensive acoustic monitoring using bottom mounted hydrophones deployed

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by the US Navy (SOSUS) has been carried out for a number of years (Clark and Charif, 1998; 2009;

Charif and Clark 2000). These studies showed acoustic detections of fin, humpback and blue whales

were frequent off the shelf edge with peaks in detections between October and January suggesting

the western seaboard is used as a migratory path. More recently Wall (2012) targeted deep canyon

habitats off the northwest during a pilot project to assess the feasibility of monitoring beaked

whales with SAM. Two SAM devices were deployed at three sites off the NW shelf edge and one on

the M3 weather buoy. These provided data for over 200 days between August 2009 and 2011.

These and other recent surveys carried out as part of oil and gas licencing obligation (e.g. Baines et

al. 2013) have highlighted the Porcupine Bight and slopes as important habitats for cetaceans and

some seabirds. These include offshore bottlenose dolphins, Risso’s dolphins, deep-diving species

such as beaked bottlenose whales and fin and the critically endangered blue whale.

The Australian oil and gas company, Woodside, have recently entered the Irish exploration market

by taking an interest in four licensed blocks in the Porcupine Basin. As part of their commitment to

evidence based management they sought to deploy SAM gear at three sites in, and adjacent to, the

Porcupine Seabight and on the shelf break. The main aim of this cruise was to deploy the SAM gear

and to conduct concurrent cetacean and seabird surveys during transit to and from the monitoring

locations.

Seabird surveys in the offshore waters around Ireland began in the 1980’s (Stone et al. 1995) with an

intensive series of at-sea surveys taking place between August 1994 and September 1997 (Pollock et

al. 1997) and between July 1999 and September 2001 (Mackey et al. 2004). These surveys provided

important baseline seasonal data on seabird distribution, abundance and density in Irish waters with

the shelf slope around the Porcupine Seabight being identified by Mackey et al. (2004) as some of

the most species rich areas in the Irish EEZ. In recent years, these data have been supplemented by

surveys undertaken on board the Celtic Explorer and Celtic Voyager during dedicated research

cruises for cetaceans and seabirds (Cetaceans on the Frontier 2009-2010 and 2012-2014) and during

select annual fisheries monitoring programs (Celtic Sea Herring Acoustic Survey 2012-2013; Blue

Whiting Acoustic Survey 2014). By using standard European Seabirds at Sea (ESAS) survey methods,

further data on seabird numbers and distribution in the Irish EEZ has been collected during this

cruise.

METHODS

This survey was conducted on board the Marine Institute’s Celtic Voyager. Opportunistic surveying

was carried out between 17 and 20 May, 2014. The survey area covered waters over the Porcupine

Bank, Porcupine Seabight and Celtic Shelf. As the survey primary aim of the cruise was to deploy

acoustic monitoring equipment, the trackline was selected to maximise deployment opportunities

during a narrow weather window. Thus cetacean and seabird surveys were conducted as though on

a platform of opportunity. The areas surveyed were chosen by Woodside to accommodate the

deployment of static acoustic equipment at their chosen site allowing the team to survey deep-

water canyon and slope habitat.

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Static Acoustic Monitoring Deployments

Static Acoustic Monitoring (SAM) arrays were to be deployed at three sites. These involved two

loggers at two sites (Belgica and Hovland Mounds) and three loggers at one site (SW Porcupine)

(Table 1).

Table 1. SAM arrays to be deployed in the Porcupine Seabight and adjacent waters.

Site

SAM equipment

Belgica Mound LF Shallow logger HF Curtin logger Hovland Mound LF Shallow logger HF Wildlife Acoustics logger SW Porcupine LF Deep Logger HF Wildlife Acoustics logger Deep CPOD

At each of the three stations where static acoustic monitoring equipment was being deployed, a CTD cast was carried out. The CTD probe recorded temperature, depth and conductivity (salinity) data throughout the drop and haul, giving duplicate data for any given depth at each station. The probe was dropped to within 10m of the seabed

Figure 1. Locations of SAM deployments during cruise CV14020

Visual Cetacean Survey

Two marine mammal observers were present on board during the survey and conducted watches

from the ships bridge wings located 4.2m above sea level. Observer effort focused on a 90-degree

arc ahead of the ship; however sightings located up to 90 degrees to port and starboard were also

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included. The observer scanned the area by eye and using 10 X 40 binoculars. Bearings to sightings

were measured using an angle board and distances were estimated with the aid of distance

measuring stick (Heinmann, 1981). Environmental data were recorded every 30 minutes using

Logger 2000 software (IFAW 2000). Sightings were also recorded using Logger 2000. Automated

position data were obtained through a laptop computer linked to GPS receiver. As this was a survey

onboard a vessel of opportunity, the survey was conducted in ‘passing mode’ and cetaceans sighted

were not approached. Sightings were identified to species level where possible, with species

identifications being graded as definite, probable or possible. Where species identification could not

be confirmed, sightings were downgraded (e.g. unidentified dolphin/unidentified whale/unidentified

beaked whale etc.) according to criteria established for the IWDG’s cetacean sightings database

(Berrow et al. 2010).

Passive Acoustic Detection Cetacean Survey

A towed hydrophone array was deployed for the duration of the survey. This array consists of a

200m cable with four (2 low and 2 high frequency) hydrophone elements situated 250mm apart in a

fluid filled tube towards the end of the cable. The hydrophone connects to an interface unit with

Neutrik XLR inputs and a 2 kHz high pass filter for the high frequency channels. From the interface

box, the high frequency channels are connected to a National Instruments 9171 soundcard while the

low frequency channels feed into a Tascam US144 mk2 ASIO soundcard. Both the high and low

frequency channels are connected from their soundcards to separate laptops via USB. This allowed

for the detection of sounds outside the capability of the computers soundcard (i.e. harbour porpoise

high frequency echolocation clicks). Detection software used during survey was PAMGUARD (freely

available at www.pamguard.org) and IFAW´s, LOGGER and Rainbow click (freely available at

www.ifaw.org). The acoustic survey track line will be recorded via an external GPS receiver linked to

the Logger software. PAMGUARD is a fusion of the IFAW suite and Ishmael and therefore has

applications such as click detectors, tonal whistle detectors, capability to calculate bearings on maps,

record a track log, spectrogram viewer, detection energy display, and has built in filters. The

collection of acoustic data during visual surveys will add an extra dimension to the monitoring

dataset. Acoustic monitoring can detect cetaceans which are beyond the visual observers view and

therefore increase the capacity of a survey. Each day all acoustic files were backed up on a 1TB

external hard-drive.

A PAM operator was present with the monitoring station and listened to the data stream in real

time. This method served to reduce the amount of post processing and allowed for the species

identification of detections where visual sightings occurred. Data analyses included the visual

inspection of all sound files on spectrograms using IFAW‟s whistle detector and porpoise detector.

All characteristics associated with detections including, inter-click interval of click trains, as well as

frequency, shape and outline of whistles will be taken into account when identifying detections to

species level (example Fig. 3). The track of all acoustic effort was mapped, with acoustic detections

classed as “sightings”, and these were overlain on the track similar to those from visuals surveys.

Seabird Survey

Surveys of seabirds at sea were conducted from Celtic Voyager between 17 and 20 May 2014. A

standardised line transect method with sub-bands to allow correction for species detection bias and

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‘snapshots’ to account for flying birds was used (following the recommendations of Tasker et al.

1984; Komdeur et al. 1992; Camphuysen et al. 2004).

Two observers (a primary observer and a scribe, who also acted as a secondary observer) worked in

rotating one hour shifts, surveying between 08:00 and 21:00 hours. Environmental conditions,

including wind force and direction, sea state, swell height, visibility and cloud cover, and the ship’s

speed and heading were noted at regular intervals during surveys. No surveys were conducted in

conditions greater than sea state 6, when high swell made working on deck unsafe, or when visibility

was reduced to less than 300m.

Seabird surveys were conducted from the platform of the bridge-wings. The platform for

observation was changed to either the port or starboard side on the basis of suitable viewing

conditions at the time (e.g. presence of glare). The platform height was 4.2m above the waterline,

providing an uninterrupted view of the survey area. The survey area was defined as a 300m wide

band operated on one side (in a 90˚ arc from the bow) and ahead of the ship. This survey band was

sub- divided (A = 0-50m from the ship, B = 50-100m, C = 100-200m, D = 200-300m, E = >300m) to

subsequently allow correction of species differences in detection probability with distance from the

observer. A fixed-interval range finder (Heinemann 1981) was used to periodically check distance

estimates. The area was scanned by eye, with binoculars used only to confirm species identification.

All birds seen within the survey area were counted, and those recorded on the water noted as ‘in

transect’. All flying birds within the survey area were also noted, but only those recorded during a

‘snapshot’ were regarded as ‘in transect’. This method avoids overestimating bird numbers in flight

(Tasker et al. 1984). The frequency of the snapshot scan was ship-speed dependent, such that they

were timed to occur at the moment the ship passed from one survey area (300m long x 300m wide)

to the next. Any bird recorded within the survey area that was regarded as being associated with the

survey vessel was noted as such (to be excluded from abundance and density calculations). Survey

time intervals were set at 1 minute. Additional bird species observed outside the survey area, during

periods of casual observations were also recorded and added to the species list for the duration of

the survey. In this report we present our daily total count data for each species across all days along

with the daily survey effort.

SAM deployment at Belgica Mound

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RESULTS

Static Acoustic Monitoring Deployments

All three SAM arrays were successfully deployed in the assigned areas (Table 2).

Table 2. Location and water depth of SAM equipment to be deployed in the Porcupine Seabight and

adjacent waters.

Site Water Depth Location

Belgica Mound 538m 51° 22.904' N 11° 37.446' W Hovland Mound 596m 52° 22.775' N 52° 22.775' N SW Porcupine 767m 51° 52.660' N 15° 01.344' W

Temperature and Salinity Profiles

Static Acoustic Monitoring (SAM) equipment was deployed at three sites. At each site following

deployment a CTD cast was made to explore whether stratification was occurring which may

interfere with the transmission of sound signals in the deep ocean. Heavily stratified water, whether

it be through temperature or salinity barriers, can restrict sound transmission, especially of low

frequency cetacean vocalisations.

Belgica Mound: Sea temperature and salinity was quite consistent throughout the profile to a depth

of 538m. There was a slight drop from 11.1°C to 10.5°C between 68 and 108m after which it was

quite stable (Fig. 2a &b).

Figure 2a and b. Results of CTD casts at Belgica Mound SAM site

Hovland Mound: Similar to Belgica mound the water was well mixed with no sign of a thermo or

halocline. There were temperature drops between 16 and 24m and between 68-80m (Fig. 3a &b)

but only small drops suggesting little stratification.

SW Porcupine: Similar to the other sites there was great consistency in temperature and salinity

throughout these profiles down to 750m at the SW Porcupine site. Temperature drops of around 1°C

occurred around between 48-96m (Fig. 4a &b).

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Figure 3a and b. Results of CTD casts at Hovland Mound SAM site

Figure 4a and b. Results of CTD casts at SW Porcupine SAM site

Marine Mammal Visual Survey

A total of only nine sightings of around 60 individual animals were recorded. Cetacean species

identified comprised long-finned pilot whale (Globicephala melas), humpback whale (Megaptera

novaeangliae), common dolphin (Delphinus delphis) and harbour porpoise (Phocoena phocoena).

Table 3. Sightings of marine mammals during cruise

Species No. Sightings No. Individuals Range of Group Size

Harbour porpoise

1 2 2

Humpback whale 1 1 -

Long-finned pilot whale 1 12 10-15

Common dolphin 1 20 -

Unidentified beaked whale 2 3 1-2

Unidentified large whale 1 1 -

Grey seal 2 2 -

Total 9 60

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Marine mammal sightings were spread out throughout the track-line (Fig. 5). The single humpback

whale was observed breaching around 6-7 km southeast of Galley Head, Co Cork while on transit

along the south coast and the harbour porpoise sighting a little further west. A single unidentified

beaked whale was observed at the first SAM site at Belgica Mound, when it surfaced within 100m of

Celtic Voyager while on station. It was not seen again but was relatively small c5m, grey in

colouration with a small dorsal fin situated two-thirds along its back. There was a distinct short

bushy blow. During transit between Belgica and Hovland Mounds two whales were seen breaching

around 2km away and a single large whale blow observed on two occasions. From the size of the

whale and behaviour they were most likely Mesoplodon sp. A group of around 12-15 long-finned

pilot whales were seen soon after this sighting.

Long-finned pilot whales, Porcupine Bank, 18 May 2014 © Ryan Wilson-Parr

It was interesting to note that no dolphins were recorded until the approaches to Galway Bay when

up to 20 common dolphins approached Celtic Voyager. They were detected on the towed

hydrophone some minutes before they were observed.

SAM deployment at Belgica Mound

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Figure 5. Map showing visual survey effort and location of sightings.

Passive Acoustic Detection Survey

Survey effort using PAM was more extensive than visual effort as it was run at night during dark.

Also PAM is dependent on sea-state and thus while high sea-states mitigated against visual sightings

it would have a minimal effect on the ability of the towed hydrophone to record detections.

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Figure 6. Map showing acoustic survey effort and location of detections.

There were surprisingly few acoustic detections and only one concurrent sighting (common

dolphins) to confirm identification. High frequency clicks were detected on 18 May on the shelf edge

but they were only detected for <10 seconds and it was thought to be a false positive porpoise

densities are much greater closer to shore. On 18 May a seismic survey was detected (bang every 12

seconds) which was likely to be that being carried out by BGP Explorer. These airguns were heard

throughout the day and night for the next 26 hours. Some clicks which were assigned to probable

beaked whale were detected but it was felt they were unlikely to be beaked whale and are not

presented.

Table 4. Acoustic detections of cetaceans during cruise

Date/Time (UTC)

Event Likely source

Visual

Low frequency

18 May/10:58 clicks Possible harbour porpoise

18 May/22:17 whistles (faint) Unidentified dolphin

20 May/11:35 whistles (faint) Possible common dolphin

20 May/21:05 whistles (faint) Common dolphin sighting

20 May/22:34 Grunt Unidentified source

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Seabird Survey

A total 977 minutes (16 hours and 17 minutes) of seabird surveys were conducted across three days

between 18 and 20 May 2014 (Table 5). An uncorrected, cumulative total of 1594 individual seabirds

of 16 species were recorded. A total of 70 seabirds were noted as ‘off survey’, outside of dedicated

survey time or associating with the vessel and as such will be excluded from future analysis of

abundance and density. Thus, the corrected total of seabird recorded during dedicated survey time

was 1524. A synopsis of daily totals for all seabird species recorded is presented in Table 6. The

greatest number of seabirds and highest species richness was encountered on the Porcupine

Seabight area on 18 May (Table 6).

Table 5. Details of daily effort, species richness and location throughout the survey period.

Date

Start

End

Effort (mins)

Species

Platform

Area

18/05/2014 09:44 21:07 346 13 Bridge-wing Porcupine Seabight

19/05/2014 08:26 18:00 451 12 Bridge-wing Porcupine Bank Shelf Edge

20/05/2014 14:26 17:26 180 9 Bridge-wing Porcupine Bank

Total

977 16

Table 6. Daily totals for all seabird species recorded between 18 and 20 May 2014. Figures in italics

represent totals of birds recorded as ‘off survey’, i.e. in association with the survey vessel or outside

of dedicated survey time, thus separate to ‘on survey’ totals (non-italics) which are to be used for

abundance and density estimates.

Species

18 May

19 May

20 May

Total

Great Northern Diver

2

2 Fulmar 91 201 6 47 3 339 9

‘Blue’ Fulmar

1

1 1 1

Bermuda Petrel (Cahow) 1 1

Sooty Shearwater 1 1

Manx Shearwater 423

105

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534 European Storm-petrel 5 2 7 30 2 42 4

Gannet 79 5 11 3 42

132 8

Pomarine Skua 2 1 5

1 7 2

Long-tailed Skua 4 3 154

1 158 4

Great Skua (Bonxie) 6 1

6 1

Puffin 4 2 6

Arctic Tern 138

138 Kittiwake 123 15 26 2 4 153 17

Lesser Black-backed Gull 3 20

1

1 3 22

Yellow-legged Gull 1 1 1 1

Great Black-backed Gull

1

1

Total 875 49 518 12 131 9 1524 70

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SPECIES ACCOUNTS

The binomial species names for the birds recorded are presented in the following species accounts,

for which taxonomy and nomenclature follows that of the Irish Rare Birds Committee (2012).

Great Northern Diver (Gavia immer): Two breeding plumage birds migrating Northwest on 19 May.

Fulmar (Fulmarus glacialis): The second most abundant species recorded with greatest numbers

observed along the Western shelf edge of the Porcupine Bank on 19 May. Two dark morph bird

originating from High Arctic breeding grounds, known as ‘Blue’ Fulmars were also noted as singles on

19 and 20 May.

Bermuda Petrel (Cahow) (Pterodroma cahow): A single Cahow was seen on 19 May 2014,

approximately 170 nautical miles West-Northwest of Slea Head, Co. Kerry on the Western

slope/shelf edge of the Porcupine Bank. It was first observed at 17:56pm, travelling alongside the

survey vessel at c.250m range, over a water depth of 1,030m whilst approaching the head of a

canyon. It was on view for a maximum of 1 minute before heading off in a South East direction. This

was the first ever sighting of this species in Irish waters and in the North East Atlantic as a whole.

Bermuda Petrel (Cahow), Porcupine Bank, 19 May 2014 © Simon Berrow Sooty Shearwater (Puffinus griseus): A single bird was seen associating with the survey vessel over

the Porcupine Seabight on 18 May.

Manx Shearwater (Puffinus puffinus): The most abundant species recorded with greatest numbers

observed over the Porcupine Seabight area on 18 May.

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Manx Shearwater, Porcupine Bank, May 2014 © Ryan Wilson-Parr

European Storm-petrel (Hydrobates pelgicus): Present across all survey days with greatest numbers

observed on 20 May when 32 were recorded over the Porcupine Bank.

Gannet (Morus bassanus): Present across all survey days in relatively low numbers. Of a total of 135

birds aged, 88.8% were adult or near adult types (ages 4, 5 and 6).

Pomarine Skua (Stercorarius pomarinus): A total of nine were seen across all three survey days.

Third summer Pomarine Skua, Porcupine Seabight, 18 May 2014 © Ryan Wilson-Parr

Long-tailed Skua (Stercorarius longicaudus): The third most abundant species encountered, largely

due to the presence of sizeable migrating flocks on 19 May when a total of 154 birds were recorded

on the Western edge of the Porcupine Bank.

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Adult Long-tailed Skua, Porcupine Bank, 19 May 2014 © Ryan Wilson-Parr

Great Skua (Bonxie) (Stercorarius skua): A total of seven were recorded over the Porcupine Seabight

on 18 May.

Puffin (Fratercula arctica): A total of six breeding plumage birds were recorded on the Porcupine

Bank on 19 and 20 May.

Arctic Tern (Sterna paradisaea): Two flocks, of 120 and 18 birds respectively, seen migrating

Northwest over the Porcupine Seabight on 18 May.

Kittiwake (Rissa tridactyla): Recorded across all survey days with greatest numbers observed on 18

May over the Porcupine Seabight. Of a total of 155 birds aged, 78% were adult types, the rest were

first year birds.

Lesser Black-backed Gull (Larus graellsii): Recorded across all survey days with greatest numbers in

association with the survey vessel over the Porcupine Seabight on 18 May.

Yellow-legged Gull (Larus michahellis): Two seen. A 3rd-summer bird associating with the survey

vessel on 18 May over the Porcupine Seabight and an adult heading West over the Western edge of

the Porcupine Bank on 19 May.

Great Black-backed Gull (Larus marinus): A single bird associating with the survey vessel on 18 May

over the Porcupine Seabight.

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Discussion

The objectives of the cruise were met. Static Acoustic Monitoring arrays were deployed at the three

sites identified before the cruise and simultaneous cetacean and seabird surveys conducted.

Cetacean sightings were low but this was to be expected at this time of year. Sightings inshore are

typically at a minimum during April and May (Berrow et al. 2010) and while seasonal changes in

offshore cetacean distribution is poorly known there are undoubtedly strong seasonal changes in the

occurrence of some species.

Resident species such as long-finned pilot whales were observed on the shelf edge while baleen

whales were largely absent. Fin, blue and humpback whale acoustic detections off the west coast

(Region D) are at a minimum in April – May (Clark and Charif, 1998; Charif and Clark, 2000). Although

sea-state was high on the western shelf edge, visibility was good and large whale blows would have

been observed if abundant. The seasonal occurrence of beaked whales is not known but two

sightings during this relatively short survey is quite high and the sighting of a Mesoplodon species at

the deployment site at Belgica Mound is very encouraging and it will be interesting to see if they are

recorded acoustically at this site.

The low number of dolphin sightings was a surprise. De Soto (2004) conducted a PAM survey to the

south of the porcupine in April to June 2000 and recorded numerous whistles presumably from

dolphins. Common dolphins are widespread and abundant off the southwest coast especially on the

continental shelf (Wall et al. 2013) but only one sighting was recorded during the present survey

around 30km to the west of the Aran Islands. We might have expected to record offshore bottlenose

dolphins but this population is highly mobile (Louis et al. 2013).

Previous offshore seabird surveys have shown that the area around the Porcupine Seabight can hold

some of the highest species diversity in the Irish EEZ (Mackey et al. 2004). The same study identified

shelf and shelf edge habitats either side of the Rockall Trough (the Hatton Bank in particular and to a

lesser extent, the Porcupine Seabight) as corridors for northbound skua migration, with greatest

numbers of long-tailed and pomarine skuas recorded in May. This cruise confirmed the presence of

both species in the study area during peak migration time with large numbers of long-tailed skuas in

particular observed along the western edge of the Porcupine Bank on 19 May. In addition, migrating

Arctic terns and great northern divers were also observed during the survey period en route to

breeding grounds in Iceland, Greenland or Arctic Canada.

The largest feeding aggregations of Irish breeding species such as gannet, kittiwake and Manx

shearwater were identified over the Porcupine Seabight. It was noted that a higher proportion of

immature or non-adult gannets and kittiwakes were recorded compared to surveys conducted in this

area during winter months (O’Brien et al. 2012; Ryan et al. 2013; O’Brien et al. 2014) suggesting that

the study area may form an important foraging area for non-breeding individuals during spring

months.

The record of a Bermuda petrel (Cahow) over the western edge of the Porcupine Bank on 19 May

represents the only at sea sighting of this species away from the eastern seaboard of North America

and certainly the first for Irish and European waters. Recent geolocators studies have shown that

failed breeding birds or non-breeding immatures can range as far East as the Porcupine Bank and the

area west of the Bay of Biscay between April and early June (Madeiros 2012). With a breeding

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population of 108 pairs in 2014 (Jeremy Madeiros pers. comm.) and a total global population of

perhaps 350 individuals, the Bermuda Petrel (Cahow) is classified as ‘Endangered’ by the IUCN Red

List (IUCN 2013). The confirmation of foraging ranges suggested in the geolocator study by the at sea

sighting during this cruise is of vital importance to better understanding the foraging ecology and

migration routes of one of the world’s rarest birds. Further surveying over deep water canyon

habitats in the Irish EEZ between April and June should hopefully provide more sightings of this

enigmatic seabird and shed light on its true status, distribution and habitat requirements here.

Continued recording over the study site through the breeding (April-June) and post-breeding (July-

September) seasons is also recommended in order to ascertain the full scale of usage as a migration

corridor for skuas and as a foraging area for both breeding and non-breeding species found at Irish

colonies.

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References

Baines, M., Reichelt, M., Coles, D., Williams, A., Griffin, D. and Corkhill, O. (2013) Marine Mammal

observers and Passive Acoustic Monitoring Operator’s Report during 3D seismic surveys off South

West Ireland for Kosmos. DCENR website [online] http://www.dcenr.gov.ie/NR/rdonlyres/B2ABEB7B-

2751-45DD-A91C-D071C8B1604C/0/201311FinalMMO1530Kosmos.pdf (accessed 17 Dec 2013).

Berrow, S. (2001) Biological diversity of cetaceans (whales, dolphins and porpoises) in Irish waters. In

Marine Biodiversity in Ireland and adjacent waters. Ed. Nunn, J. Pages, 115-119.

Berrow, S., Whooley, P., O’Connell, M. and Wall, D. (2010) Irish Cetacean Review (2000-2009). Irish

Whale and Dolphin Group, 60pp. ISBN 0-9540552-4-1.

Camphuysen, K. J., Fox, A. D., Leopold, M. F. and Petersen, I. K. (2004) Towards standardised

seabirds at sea census techniques in connection with environmental impact assessments for offshore

wind farms in the U.K.: a comparison of ship and aerial sampling methods for marine birds, and their

applicability to offshore wind farm assessments. NIOZ report to COWRIE (BAM – 02-2002), Texel,

37pp.

Charif, R.A. and Clark, C.W. (2000) Acoustic monitoring of large whales to the west of Britain and

Ireland using bottom-mounted hydrophone arrays, October 1996-September 1998. JNCC Report No.

313, 1-35.

Charif, R.A. and Clark, C.W. (2009). Acoustic monitoring of large whales in deep waters north and

west of the British Isles: 1996-2005. Preliminary Report. Cornell University Lab of Ornithology

Bioacoustics Research Program, Technical Report 08-07 for UK Department of Energy and Climate

Change’s offshore energy Strategic Environmental Assessment programme.

Clark, C. W., Charif, R.A. (1998) Acoustic monitoring of large whales to the west of Britain and

Ireland using bottom-mounted hydrophone arrays, October 1996-September 1997. JNCC Report No.

281, 1-25.

Hammond, P. S., Benke, H., Berggren, P., Borchers, D.L., Buckland, S.T., Collet, A., Heide-Jorgensen,

M.P., Heimlich-Boran, S., Hiby, A.R., Leopold, M.F. and Oien, N. (2002) Abundance of harbour

porpoise and other cetaceans in the North Sea and adjacent waters. Journal of Applied Ecology 39,

361-376.

Hammond, P.S., K., Macleod, D., Gillespie, R., Swift, A., Winship, M.L. Burt A. Cañadas J.A. Vázquez V.

Ridoux, G. Certain, O. Van Canneyt S. Lens, B. Santos E. Rogan, A. Uriarte, C. Hernandez, R. Castro

(2009) Cetacean Offshore Distribution and Abundance in the European Atlantic (CODA). Final Report.

Hammond, P.S., Macleod, K., Berggren, P., Borchers, D.L., Burt, L., Cañadas, A., ... Vázquez, J.A.

(2013) Cetacean abundance and distribution in European Atlantic shelf waters to inform

conservation and management. Biological Conservation 164, 107-122.

20

Heinemann, D. (1981) A Range Finder for Pelagic Bird Censusing. Journal of Wildlife Management

45(2): 489-493.

Irish Rare Bird Committee (2012) The Irish Bird List. www.irbc.ie/topbar/IrishList/IRBC_Irish

List(31122012).pdf (accessed May 2014).

IUCN (2013) The IUCN Red List of Threatened Species 2013.2

http://www.iucnredlist.org/details/22698088/0 (accessed May 2014).

Komdeur, J., Bertelsen, J. and Cracknell, G. (ed.) (1992) Manual for Aeroplane and Ship surveys of

Waterfowl and Seabirds, IWRB Special Publication No. 19. Ministry of the Environment, National

Environmental Research Institute, Dept. Of Wildlife Ecology, KalØ, Denmark.

Louis, M., Viricel, A., Lucas, T., Peltier, H., Alfonsi, E., Berrow, S., Brownlow, A., Covelo, P., Dabin, W.,

Deaville, R., de Stephanis, R., Gally, F., Gauffier, P., Penrose, R., Silva, M.A., Guinet, C. and Benoit S-B.

(2014) Habitat-driven population structure of bottlenose dolphins, Tursiops truncatus, in the North-

East Atlantic. Molecular Ecology. 23, 857-874.

Mackey, M., Ó Cadhla, O., Kelly, T.C., Aguilar de Soto, N. and Connolly, N. (2004) Cetaceans and

Seabirds of Ireland’s Atlantic Margin. Volume 1 – Seabird distribution, density and abundance.

Report on research carried out under the Irish Infrastructure Programme (PIP): Rockall Studies

Group (R SG) projects 98/6 and 00/13, Porcupine Studies Group project P00/15 and Offshore

Support Group (OSG) project 99/38. University College Cork.

Madeiros, J. (2012) 2011/2012 Cahow Recovery Program Breeding Season Report. Terrestrial

Conservation Division, Department of Conservation Services, Ministry of Public Works, Bermuda

Government.

O’Brien J., et al (2012) Cetaceans on the Frontier Survey 2012. Cruise Report to the Marine Institute, Oranmore, Galway, Ireland. O’Brien J., et al (2014) Cetaceans on the Frontier Survey 2014. Cruise Report to the Marine Institute, Oranmore, Galway, Ireland. O’Brien, J., Berrow, S.D., McGrath, D. and Evans, P.G.H. (2009) Cetaceans in Irish Waters: A Review of

Recent Research. Biology and Environment. 109B, No. 2, 63–88.

O’Brien, J., Beck, S., Wall, D. and Pierini, P. (2013) Developing Acoustic Monitoring Techniques. In

Marine Mammals and Megafauna in Irish Waters ‒ behaviour, distribution and habitat use (Final

report to the Mariner Institute under the SeaChange Programme and the National Parks and Wildlife

Service. PBA/ME/07/005(02).

Pollock, C.M., Reid, J.R., Webb, A., and Tasker, M.L. (1997) The distribution of seabirds and

cetaceans in the waters around Ireland. JNCC Report No. 267.

Reid, J.B., Evans, P.G.H. and Northridge, S.P. (2013) Atlas of Cetacean Distribution in Northwest

European Waters. Joint Nature Conservation Committee. UK

21

Rogan, E. and Berrow, S.D. (1995) The management of Irish waters as a whales and dolphin

sanctuary. In Developments in Marine Biology, 4. Whales, seals, fish and man, Eds Blix, A.S., Walloe,

L. and Ulltang. O. Proceedings of the International Symposium on the Biology of Marine Mammals in

the North East Atlantic. Tromso, Norway, 29 November - 1 December 1994. Elsevier, Amsterdam,

Netherlands. p 671- 682.

Ryan, C., et al (2013) Cetaceans on the Frontier Survey 2013. Cruise Report to the Marine Institute, Oranmore, Galway, Ireland. De Soto, N., Rogan, E., O’Cadhla, O., Gordon, J.C.D., Mackey, M. and Connolly, N. (2004) Cetaceans

and seabirds of Ireland’s Atlantic Margin: Volume III Acoustic Surveys for Cetaceans. Report on

research carried out under the Irish Infrastructure Programme (PIP): Rockall Studies Group (RSG)

projects 98/6 and oo/3, Porcupine Studies Group project P00/15 and Offshore Support Group (OSG)

project 99/38. 51pp.

Stone C.J., Webb A., Barton C., Ratcliffe N., Reed T.C., Tasker M.L,. Camphuysen C.J and Pienkowski

M.W. (1995) An Atlas of seabird distribution in north-west European waters. Joint Nature

Conservation Committee, Monkstone House, City Road, Peterborough, PEI IJY United Kingdom.

Tasker, M.L., Jones, P.H., Dixon, T., & Blake, B.F. (1984) Counting seabirds at sea from ships: a review

of methods employed and a suggestion for a standardised approach. Auk 101: 567-577.

Wall, D. (2012) Pilot study to assess the feasibility of acoustic monitoring for beaked whales off the

NW shelf. Final report to the Petroleum Affairs Division.

Wall, D., Murray, C., O’Brien, J., Kavanagh, L., Wilson, C., Glanville, B., Williams, D., Enlander, I., Ryan,

C., O’Connor, I., McGrath, D., Whooley, P. and Berrow, S. (2013) Atlas of the distribution and relative

abundance of marine mammals in Irish offshore waters: 2005 – 2011. Irish Whale and Dolphin

Group.