Marine Mammal Monitoring in Broadhaven Bay 2012

Progress Report to RSK Environment Ltd. February 2013

Coastal and Marine Research Centre Environmental Research Institute University College Cork Ireland

Damien Haberlin Pia Anderwald Anja Brandecker Clodagh Collins Kathrin Kruegel Michelle Cronin

Coastal and Marine Research Centre Environmental Research Institute University College Cork Ireland

Citation. Haberlin, D., Anderwald, P., Brandecker, A., Collins, C., Kruegel, K. and Cronin, M. (2013). Marine mammal monitoring in Broadhaven Bay 2012. Progress Report to RSK Environment Limited Group. Coastal and Marine Research Centre, University College Cork, Ireland.

CONTENTS

Summary 1

1. Introduction 4 1.1. Background 4 1.2. Broadhaven Bay SAC 6 1.3. Marine Mammal Fauna 6 1.4. Aims 8

2. Methods 9 2.1. Study area 9 2.2. Visual effort 10 2.2.1. Line-transects 10 2.2.2. Cliff watches – fieldwork 11 2.2.3. Temporal occurrence 12 2.2.4. Spatial distribution 15 2.3. Acoustic effort 17 2.3.1. PODs 17 2.3.2. Data processing 18 2.3.3. Analysis 19 2.4. Photo-ID 20 2.4.1. Fieldwork 20 2.4.2. Analysis 21

3. Results 23 3.1. Visual effort 23 3.1.1. Seasonal occurrence 28 3.1.2. Models of temporal occurrence 39 3.1.3. Spatial distribution 33 3.2. Acoustic effort 52 3.3. Photo-ID 60

4. Discussion 63 4.1. Spatial distribution 63 4.2. Temporal patterns of harbour porpoise occurrence 64 4.3. Bottlenose dolphin photo-ID 66 4.4. Effects of construction 66 4.4.1. Anthropogenic impacts: monitoring considerations 67

Acknowledgements 69

References 70

SUMMARY Following on from 2002, 2005 and 2008-11, the marine mammal monitoring programme in Broadhaven Bay, Co. Mayo, NW Ireland, was continued in 2012. Effort consisted of 43 days (238 one-hour scans in good viewing conditions) of cliff-based observations between January and November, 1 line-transect (offshore), 3 photo-ID trips and year-round acoustic monitoring using C-PODs at 4 listening stations within the bay. A total of 8 marine mammal species was recorded from cliff-based observations in 2012, comprising minke whale, bottlenose dolphin, common dolphin, Risso’s dolphin, white-beaked dolphin and harbour porpoise as well as grey and harbour seals. Common dolphin accounted for the highest number of sightings (n=19), followed by grey seal (n=16) and bottlenose dolphin (n=12). Based on data from all years combined, bottlenose and common dolphin, harbour porpoise and grey seal occur within the study area throughout the year, while harbour seal has only been positively identified between March and September, and Risso’s dolphin between June and September. Minke whales have been observed between March and November, and in January. Additional species observed within the study area during 2012 included 10 sightings of basking shark.

Using data from all years (i.e. 2002, 2005, 2008-2012) spatial differences in habitat use between minke whales, bottlenose and common dolphins, and grey and harbour seals, were quantified in a classification tree with depth and distance from the tidally active area around Erris Head as explanatory variables. Bottlenose dolphins could be successfully differentiated by their preferential use of the shallower areas of Broadhaven Bay (<30m; and particularly Rossport Bay) from common dolphins and minke whales, which both preferred deeper waters in the outer and western parts of the bay (>30m). Half of the harbour seal sightings could be spatially differentiated from bottlenose dolphins by their generally closer proximity to the tidally active area around Erris Head, while grey seal sightings were distributed in equal proportions across all three categories, reflecting their widespread distribution throughout Broadhaven Bay.

The daily presence / absence of the five most frequently (visually) recorded species, again using data from all years, was investigated with respect to construction activity, environmental (temperature and tidal state) variables and correction parameters for observer

effort, yearly and seasonal patterns using logistic regressions. The presence of construction activity was not significant in any of the final models for the presence of the five species, suggesting a lack of short-term negative effects. This result was consistent between different categories of construction activity. However, significant inter-annual differences were detected in the presence of all five species when corrected for the other parameters in the model. These patterns showed no obvious relationship with years of construction activity for any of the five main species recorded. Both minke whales and common dolphins declined in 2012 compared with 2011, but have not changed significantly compared to 2002 records (reference level), while bottlenose dolphin presence remained relatively constant between 2011 and 2012, remaining lower than 2002 records. Grey and harbour seals showed similar declines in sighting rates during 2005, 2008, 2009 (all with construction activity) by comparison to 2002 (reference level), however their occurrence during 2011-2012 (without construction activity) was also lower than during 2002, with a quite significant decline in presence for both species in 2012.These patterns were not linear with relative intensities of construction between years. Interpretation of these results is difficult due to the lack of a pre- construction period and gaps in monitoring effort during earlier years without construction activity (i.e. 2003-04 and 2006-07), which could have provided information about natural inter-annual variations in occurrence.

Harbour porpoise detection rates from C-PODs at LS4 (Gubastuckaun) and LS2 (inner bay) were analysed with respect to time of day, tidal state, Julian day and the presence or absence of boat sonar using a Generalised Additive Model for the years 2009 to 2011. With the exception of tidal state, all explanatory variables were significant at both LS4 and LS2, with porpoise detection rates being highest during the night and at dawn, showing a seasonal peak during winter, and a negative relationship with the presence of boat sonar, which indicates avoidance of boats.

After the 2012 field season, the Broadhaven Bay bottlenose dolphin photo-ID catalogue numbers 185 individuals (139 recognisable from both sides, 46 left, and 44 right sides). Individual dolphins were photographed in up to 12 different encounters between September 2008 and August 2012, and the time period over which individuals were seen has extended up to the full four years of uninterrupted photo-ID effort. This indicates a relatively high degree of site fidelity, especially when considering the small size of the study area. Numerous matches with animals from Connemara, Galway Bay and Donegal Bay, as well as single

matches with dolphins off Co. Dublin and from the Moray Firth indicate large home ranges for individuals visiting Broadhaven Bay. However, no matches were found with animals from the Shannon Estuary or eastern part of the Irish Sea.

1. INTRODUCTION

1.1. Background Noise from underwater industrial construction activity such as pipe laying, rock-trenching or dredging has the potential to mask acoustic communication by marine mammals, cause behavioural changes, habitat displacement, or hearing damage (Würsig & Evans, 2001; National Research Council, 2005; Novacek et al., 2007). However, sensitivity to noise can vary according to species, season, level of background noise, relative importance of habitat to a particular species, behavioural state, and habituation of individuals (Myrberg, 1990; Würsig & Evans, 2001). If an important feeding habitat is affected by intense anthropogenic noise, animals may be forced to remain in the area despite suboptimal conditions or even potential risk of injury, such as damage to ear structures (e.g. Richardson et al., 1995). Due to the sensitivity of marine mammals, and their protected status, mitigation measures are carried out before and during construction activities in areas where marine mammals are known to occur or have been sighted prior to activities beginning. These include ramp-up procedures (the gradual increase of sound intensity) and the use of dedicated observers on- board construction vessels with the authority to postpone or stop construction work if marine mammals are present in the immediate vicinity. The implementation of dedicated pre-, during and post-construction monitoring programmes allows for a contribution to the assessment of whether construction works in a given area have a negative effect on the local marine mammal fauna, and if so, the severity of this effect (e.g. short- vs. long-term habitat displacement; unusual behaviour during particular aspects of construction activity). Following plans for the construction of an underwater gas pipeline from the Corrib Gas Field (65km offshore) to its landfall site near Glengad in Broadhaven Bay, Co. Mayo (Figure 1), the present marine mammal monitoring programme was initiated in 2001/02 (RSK, 2008) by Enterprise Energy Ireland Ltd, and continued by Shell Exploration and Production Ireland Ltd (SEPIL). The project is managed independently by RSK Environment Ltd (RSK) and undertaken by CMRC. It has continued in each year of construction activity, during 2002, 2005, and continuously (including winter months) since 2008 (Ó Cadhla et al., 2003; Englund et al., 2006; Coleman et al., 2009; Visser et al., 2010; Anderwald et al., 2011).

To date, construction work within Broadhaven Bay (hereafter also referred to as the bay) has involved:

 2002: acoustic & ROV surveys, dredging, trenching  2005: acoustic & ROV surveys, dredging, trenching  2008: acoustic & ROV surveys, dredging  2009: acoustic & ROV surveys, dredging, trenching, pipe-laying, rock placement  2010: acoustic surveys, rock placement  2011: no marine construction or survey activity  2012: no marine construction or survey activity

The construction activity inevitably resulted in an associated increase in boat traffic within the Bay (up to a peak of 43 vessels at one point during June 2009). These vessels included construction vessels, the 300m pipe-laying vessel Solitaire, utility boats and numerous safety Rigid Inflatable Boats (RIB’s) within an area which is normally only used by small local fishing boats. Construction works after 2010 have concentrated on the pipeline route between the landfall site and the terminal with no offshore activity. The laying of the umbilical, which will provide hydraulic power, chemicals and controls for the offshore wellheads, and will therefore involve more offshore construction works, is currently planned for 2013. Mitigation measures during offshore construction include a) the use of marine mammal observers (MMOs) on board construction vessels, and b) a code of conduct for vessels and personnel operating within Broadhaven Bay candidate Special Area of Conservation (cSAC). Within this code of conduct a number of measures to mitigate impacts are included, such as ‘soft-start’ to certain activities (acoustic surveys.) (NPWS, 2007).

1.2. Broadhaven Bay cSAC Broadhaven Bay was designated by the National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government (NPWS), as a candidate Special Area of Conservation (cSAC) in 2000. It was put forward for this designation due to: (i) The presence of four key marine/coastal habitat types listed under Annex I of the EU Habitats Directive on the Conservation of Natural Habitats and of Fauna and Flora (Habitats Directive: 92/43/EEC, 1992). These habitats are: Atlantic salt marsh, tidal mud and sand flats, reefs and large shallow bay; (i) The presence of a number of unusual marine communities and species; (ii) The seasonal presence of wintering wildfowl, and breeding terns in summer (Sterna spp.).

Furthermore, the inner part of Broadhaven Bay, known as Rossport Bay (Figure 1), is designated as a Special Protection Area (SPA) and the nearby Glenamoy Bog complex SAC is important for wintering wildfowl species such as the brent goose (Branta bernicla).

1.3. Marine Mammal Fauna in Broadhaven Bay The waters off NW Ireland are recognised as an important cetacean habitat based on historical information from whaling operations in northwest Co. Mayo (Fairley, 1981), sightings records collected by volunteers for the Irish Whale and Dolphin Group (IWDG; Berrow et al., 2002) and dedicated offshore surveys (Gordon et al., 1999; Ó Cadhla et al., 2004). All marine mammals occurring in Irish waters are legally protected the Wildlife Act (1976; http://www.irishstatutebook.ie/ 1976/en/act/pub/0039/index.html) and the EU Habitats Directive (1992; EEC, 1992). All cetaceans are listed under Annex IV of the Habitats Directive (species of community interest in need of strict protection). The harbour porpoise (Phocoena phocoena) and bottlenose dolphin (Tursiops truncatus), as well as the Atlantic grey seal (Halichoerus grypus) and harbour seal (Phoca vitulina vitulina), and European otter (Lutra lutra), are additionally listed under Annex II (species of community interest whose conservation requires the designation of Special Areas of Conservation (SAC’s)).

Of the 24 cetacean species known to occur in Irish waters, from both sightings and strandings data (Berrow, 2001; Berrow et al., 2002; O’Brien et al., 2009), nine have been recorded in Broadhaven Bay, Co. Mayo, during the course of the present monitoring programme (Ó Cadhla et al., 2003; Englund et al., 2006; Coleman et al., 2009; Visser et al., 2010; Anderwald et al., 2011). In addition, the area represents an important habitat for both grey and harbour (common) seals, as well as otters. Bottlenose dolphin, Risso’s dolphin (Grampus griseus), short-beaked common dolphin (Delphinus delphis) and Atlantic white-sided dolphin (Lagenorhynchus acutus) sightings have included groups accompanied by calves (and newborn animals in the case of bottlenose dolphins), while minke whale (Balaenoptera acutorostrata), sei whale (Balaenoptera borealis) ,killer whale (Orcinus orca), Risso’s, common and bottlenose dolphins, harbour porpoise, grey and harbour seals have all been observed foraging or feeding in the area.

Broadhaven Bay has been found to be an area of importance for marine mammals due to the following:

 High species diversity,  The regular occurrence of Annex II marine mammal species,  The possibility of the bay and/or its surrounding waters representing a calving or nursery area for bottlenose dolphins and other odontocete species,  The nearby Inishkea Islands are one of the most important breeding colonies for grey seals in Ireland, and have therefore been designated as an SAC (Ó Cadhla et al., 2007; Cronin et al., 2007) and  its use as a foraging ground by at least nine marine mammal species, including Annex II species.

1.4. Aims of the monitoring programme for marine mammals The monitoring programme for marine mammals in the bay aims to examine the potential impact of construction activities from the installation of the Corrib Gas Pipeline on marine mammals within the area of the Broadhaven Bay cSAC. It combines land-based observations from cliff-top vantage points, boat-based line-transect surveys, photo-identification and passive acoustic monitoring. The objectives of the monitoring programme include:

1. To provide an assessment of marine mammal occurrence and habitat use in the waters of Broadhaven Bay cSAC based on results from visual (cliff-top and boat-based) and acoustic survey methods and photo identification. 2. To determine whether changes in marine mammal habitat use of Broadhaven Bay cSAC exist between the pre-construction, during construction and post-construction phases of the Corrib Offshore Gas Project; 3. To collaborate with NPWS and RSK in the development of a monitoring plan and mitigation methods to minimise the impacts of construction activities on marine mammals during the period of construction work. 4. To further contribute to the scientific knowledge base regarding marine mammals on the west coast of Ireland.

5. METHODS 1.5. Study area Broadhaven Bay is located on the north-west coast of Co. Mayo. It has a northward aspect and lies between Erris Head to the west and Kid Island to the east, which lie approximately 8.6km apart (Figure 1). The bay is relatively shallow, with depths less than 50m. Tidal fronts occur primarily around Erris Head. There are a number of narrower shallow tidal inlets and estuaries, including Sruwaddacon Bay, which inputs into inner Broadhaven Bay via ‘Rossport Bay’ in the east of the study area.

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Figure 1. Broadhaven Bay and the surrounding area. Green stars represent the sites for land-based watches, with Gubastuckaun and Doonanierin being the primary sites, and Pollacoppul used only for boat counts during days of adverse weather conditions. Red circles represent the four listening stations (LS) for acoustic monitoring using POD’s.

1.6. Visual effort Both land- and vessel-based surveys for marine mammals in 2012 followed the same field protocols, using the same observation sites for cliff-top watches, as in previous years of the monitoring programme (Ó Cadhla et al., 2003; Englund et al., 2006; Coleman et al., 2009; Visser et al., 2010; Anderwald et al., 2011: Anderwald et al., 2012). This enables a more robust comparison of data between years.

1.6.1. Line-transects As in 2008-2011, line-transects were carried out on-board the 40ft sea-angling boat ‘An Gearóidín’, with an observer height of approximately 3m above sea level. One offshore line- transect was conducted (29th May 2012) off Erris Head using the same track lines as in 2011 (Anderwald et al., 2012), at a speed of roughly 10 knots (Figure 2). To ensure optimal sighting conditions, surveys were only carried out during summer months in sea states lower than Beaufort Force 3, and at swell heights of less than 1.5m. Two observers scanned a 90° angle from the bow to the port and starboard sides, recording all sightings of marine mammals, basking sharks, sunfish or turtles along with their GPS positions, group size and composition, direction of travel and behaviour. Line-transect surveys are especially useful in providing data on the spatial distribution of the more elusive marine mammal species (such as harbour porpoise, grey and harbour seals) independently from the more frequent cliff-based watches, since the detection probability particularly for these species decreases with increasing distance from the static observation points.

Figure 2. Offshore transect lines in Broadhaven Bay used during 2012. The two stars indicate the cliff-based observation sites.

1.6.2. Cliff watches - fieldwork Observers were positioned at two observation sites: at Gubastuckaun (62m above mean sea level (MSL)) and Doonanierin Point (54m above MSL; Figure 1), which between them provide a view over the entire study area of Broadhaven Bay (including the landfall site of the pipeline at Glengad from Doonanierin Point) up to ca. 8km offshore. Visual monitoring was carried out during all daylight hours in favourable weather conditions (sea state < Beaufort Force 4 and visibility ≥7km) throughout the year. Whenever possible, two observers were positioned at each site, one scanning the study area with handheld binoculars (7x50; Steiner), the other with a telescope (Kowa) equipped with a 32x wide-angle eye-piece. Scans lasted 1-hour ± 15min (allowing for variation in time needed to record sightings and determine positions of animals using a theodolite (Sokkia DT500)). Each scan was followed by a 1-hour break to achieve a degree of independence between scans and to allow observers to rest their eyes. Environmental conditions (sea state, swell height, visibility, precipitation and extent of glare) were recorded at the start of each scan. All marine mammal, basking shark, sunfish and turtle sightings were recorded, noting their position (relative to the

observation point) using a theodolite, group size and composition, direction of travel, behaviour, and whether the group was a re-sighting (from the same platform) or duplicate (repeat sighting of animals already seen from the other site). Where feasible, animals were tracked by one observer for as long as possible, noting their positions and behaviour every 10 minutes. Animals sighted during a break between scans were recorded as opportunistic sightings. In addition, boat activity within the bay was recorded, with vessel type, relative size, activity and position of each boat noted at the end of each scan.

2.2.3. Temporal occurrence Due to the low frequency of vessel-based line-transect surveys in comparison to land-based observations, all analyses of trends in species occurrence were based on effort-related observations from the cliffs only, in order to ensure comparability between years and months. While land-based observation platforms have the advantage of enabling representative temporal coverage of a limited coastal area, there is the possibility that the same animals are counted more than once because they may use the same location for a prolonged period of time or leave temporarily and return later. If a group of animals leaves the study area and the same species is observed in a subsequent scan, it is not usually possible to tell whether the same individuals have returned, or if the sighting represents a new group of animals. These issues would be addressed more thoroughly in abundance estimates for the area, however, since the main objective of the present analysis was the examination of the use of the study area by different marine mammal species, rather than abundance estimates. Seasonal occurrence patterns of the five most frequently recorded species (minke whale, bottlenose and common dolphins, grey and harbour seals) were therefore not expressed as distinct sightings per unit effort. Instead, occurrence was expressed as the proportion of scans in which the species were present relative to the total number of scans for a particular month, as well as the average number of individuals per scan respectively (i.e. allowing for repeat sightings of the same individuals between scans). Harbour porpoises were excluded from analyses of effort-related sightings since they could only be visually detected from the cliffs in the calmest of sea conditions, and sighting rates would therefore not be representative. Instead, temporal presence of harbour porpoises was examined using acoustic devices (see below).

Since fieldwork protocols differed between years, scans to be included in the analysis were selected based on the following criteria in order to make units of effort comparable over the entire duration of the project: - Scan duration: a minimum of 45min. Scans could last up to 120min depending on cetacean and boat activity in the bay (i.e. up to half a scan could be spent obtaining theodolite positions and recording). However, if a scan lasted more than 120min (2 x minimum duration of 45min + 30min break in between), it was counted as two separate scans; - The time interval between scans: a minimum of 30min. If the break was less than 30min, and the difference between the minimum break duration and the following scan resulted in a scan of longer than 45min, the record was included (e.g. a 20min break followed by an 80min scan would have resulted in a 70min scan after the minimum 30min break, and would therefore have been included), and; - Weather conditions: sea state less than Beaufort Force 4; swell height less than 2m; visibility over 7km.

The temporal presence of marine mammals in an area can be influenced naturally by parameters such as time of year, state of tide, or water temperature. These factors may directly or indirectly influence the availability and local abundance of prey species. To try and identify any negative effects from construction activities on marine mammal occurrence vs. natural temporal fluctuations simultaneously in Broadhaven Bay throughout the study period, a model for the presence of the five most frequently observed species was constructed with the following explanatory variables:  Sea surface temperature (SST),  SST gradient,  Tidal state,  Sea state,  Daily observer effort,  Construction activity presence or absence, and  Year.

Only the months of June to September received coverage in each year of the monitoring programme since 2002. Statistical analysis of temporal occurrence patterns was therefore

restricted to these four months. Since scans within the same day are not independent from one another (thus violating the assumption of independence between data points for statistical analysis), the data were summarised by species presence/absence per day for the most frequently recorded species (this analysis excluded harbour porpoise).

The effects of daily construction activities on the temporal occurrence of the five most frequently observed species were first investigated separately under the following categories: a) acoustic survey, b) ROV survey, c) general survey (i.e. including both acoustic and ROV surveys), d) dredging / backfilling, e) rock trenching, f) pipe laying, g) general construction (including dredging / backfilling, rock trenching or pipe laying), and h) any survey/construction activity (i.e. all of the above categories). For each species, the category showing the strongest effect on its occurrence in exploratory analysis was then included in the model.

Daily composites of sea surface temperature (SST) data were downloaded at 0.25° resolution from NASA (http://poet.jpl.nasa.gov source: GHRSST L4 AVHRR OI) for each day of cliff- based surveys. In addition to the SST data point closest to Broadhaven Bay (at 54.38°N, 9.88°W), adjacent data points up to a distance of 0.5° were extracted, resulting in 25 SST data points for the wider area covering 1° latitude x 1° longitude centred on Broadhaven Bay. Following deletion of points which fell on land, an SST coefficient of variation, termed the

‘SST gradient’, was calculated from the remaining data as (SSTMax – SSTMin) / SSTMax. A high variation in SST over relatively small distances can be an indication of a front with increased primary productivity, which attracts marine mammal prey and can thus influence distribution patterns at larger scales (e.g. Valiela, 1995; Bjørge, 2001).

The tidal state was expressed as the difference in water height between high and low water for the period that a scan fell into, and was then averaged over all scans per day. This gave a measure of the relative amount of water exchanged between tidal cycles per day, which may in turn influence the distribution and behaviour of marine mammal prey species within the bay (i.e. differences between periods of spring and neap tides).

Sightings efficiency for marine mammals both from boats and from land is influenced by a number of environmental parameters, the most important being sea state (e.g. Buckland et al., 1993; Hammond et al., 2002). The average sea state during scans per day was therefore

incorporated in the models as a correction parameter for the detectability of animals. A second correction parameter was the average number of scans per day between the two sites at Gubastuckaun and Doonanierin Point, which was included as the measure for effort. Finally, ‘Year’ and ‘Julian day’ were both incorporated in the models in order to account for inter-annual and natural seasonal differences in species occurrence between June and September respectively. The presence / absence of each of the five most frequently recorded species was then modelled against the explanatory variables using Generalised Additive Models (GAM’s; Hastie & Tibshirani, 1990) with a binomial distribution and logit link function. However, the GAM’s indicated largely linear relationships between the continuous explanatory variables and the response variable for all five species, and the models were therefore re-fitted using a logistic regression. All explanatory variables were simultaneously included, and model selection was performed in a stepwise backward manner using Akaike’s Information Criterion (AIC; Burnham & Anderson, 2002) first, and then the deviance test.

In summary, the 5 models were of the following form: - Response variable: species presence / absence (for minke whale, bottlenose dolphin, common dolphin, grey seal and harbour seal) - Explanatory variables: o Smooth terms: - Julian day - Sea state - Average number of scans between both observation sites / day - Range in water height between low and high water (m) - Sea surface temperature (SST) - SST gradient o Factors: -Year (2002(= reference level); 2005; 2008; 2009; 2010; 2011; 2012) - Construction activity

2.2.4. Spatial distribution Theodolite angles to animals recorded in the field were used to derive Irish National Grid co- ordinates (easting and northing) via trigonometric calculations. Calculations took the following into account: curvature of the earth; height of cliff observation sites above sea level; tidal height at the time of each sighting record; eye height of the theodolite for each record; and bearing from due east of the theodolite “zero” target, relative to the cliff site

locations. The co-ordinates were plotted in ArcGIS (Version 10.0) using the relevant scanned and geo-referenced section of the Admiralty chart 2703 “Broad Haven Bay and Approaches” as a background.

The possibility of niche differentiation between the five most frequently recorded marine mammal species (minke whale, bottlenose and common dolphins, grey and harbour seals) with respect to fine-scale spatial habitat use within Broadhaven Bay was investigated using a classification tree, based on the parameters depth, slope and distance from Gubastuckaun (i.e. a tidally active area).

Bathymetry data were digitised from the Admiralty chart 2703 “Broad Haven Bay and Approaches”. Slope was derived from the depth data by first creating a Triangular Integrated Network (TIN), which was subsequently converted into a raster using the ArcView extensions 3D-Analyst and Spatial Analyst 3.3, respectively. Sightings positions were then linked with the nearest available data point of each environmental variable via the spatial join function in ArcMap 10.0.

In order to reduce the risk of violating independence between sightings positions, any tracking positions or positions of possible re-sightings of the same animals taken within one hour of each other were deleted. A classification tree was then constructed based on the remaining sightings positions, with species as response variable, and depth, slope and distance from Gubastuckaun as explanatory variables. Classification trees split the data repeatedly into two homogeneous groups, so that between-group variation is as large as possible and within-group variation as small as possible. The optimal grouping is calculated automatically by the software. The optimal tree size (i.e. number of splits necessary) is then calculated as a trade-off between the goodness of fit and the complexity of the tree (i.e. number of branches), similar to Akaike’s Information Criterion (AIC; Burnham & Anderson, 2002). Using the rpart-library in R, the optimal tree size was selected by cross-validation and application of the one standard deviation rule (Zuur et al., 2007).

2.3. Acoustic effort Passive acoustic monitoring (PAM) is frequently used in the study of cetaceans (e.g. Gillespie et al., 2005; Verfuß et al., 2007; Scheidat et al., 2008; Simon et al., 2010), and is especially valuable during times of darkness and adverse weather conditions, when effective visual monitoring is limited. It is a cost-effective monitoring method, which can provide continuous monitoring for prolonged periods of time.

2.3.1 PODs PODs (POrpoise Detectors) are automated, stationary, passive acoustic data loggers that register and analyse information of echolocation clicks (e.g. time of occurrence, length and amplitude). Both T-PODs (analogue Timed POrpoise Detectors, which log clicks produced by the target species) and C-PODs (digital Cetacean-PODs with a frequency range of 20- 160kHz, designed to log information of echolocation clicks of all odontocetes except sperm whales( http://www.chelonia.co.uk/about_the_cpod.htm) were used in this study. All T-PODs were set by using TPOD.exe version 8.24, the most up to date version of T-POD software available for setting T-PODs, viewing downloaded files, and data analysis. T-PODs are no longer in production, although technical support is still available from the manufacturer (Chelonia Ltd, UK). The C-POD, developed in 2008, has superseded the T- POD, and the accompanying software has been updated repeatedly. All C-POD data collected between 2009 and 2011 were therefore re-analysed using the version 2.021 of the software CPOD.exe. Also for the acoustic data collected in 2012 this version were used to allow a comparability of the results. Since construction plans for 2002 had involved rock and sediment excavation within the Inner Broadhaven Bay area (also termed Rossport Bay; see Figure 1), and potentially drilling and blasting of bedrock along the inshore pipeline route, acoustic monitoring was concentrated within Rossport Bay (where noise levels and other environmental impacts were expected to be highest). After an initial testing and calibration period in 2002, three fixed listening stations (LS 1-3; Figure 1) were set up across the outer delineation of Rossport Bay, creating an ‘acoustic detection gateway’, theoretically detecting any echolocating odontocetes entering or leaving the area. These three listening stations were deployed 500m apart in a straight line along a north to south axis at an average depth of 17m at high tide (i.e. 5m above the seafloor; Ó Cadhla et al., 2003; Englund et al., 2006).

C-PODs were deployed for the first time in Rossport Bay in April 2009. The C-POD off Gubastuckaun (LS4; Figure 1) was introduced in July 2009, and was deployed at a depth of 37m. Acoustic monitoring was carried out at all four listening stations from November 2009 throughout the winter months for the first time since the onset of marine mammal monitoring in Broadhaven Bay. During the winter of 2010/11 and 2011/12, two C-PODs remained deployed at LS2 in the centre of Rossport Bay and at LS4 off Gubastuckaun, respectively, in order to maintain year-round acoustic coverage, while minimising the risk of equipment loss due to high swell during the winter months. In order to ensure comparability between months, all seasonal trends presented in this report are based on C-POD detections since April 2009.

2.3.2. Data processing C-POD data were downloaded from a removable Secure Digital (SD) memory card onto a PC. Raw data are stored by the software CPOD.exe (version 2.021; www.chelonia.demon.ac.uk) in CP1-files. The software uses a specific algorithm (KERNO classifier) to identify patterns of echolocation click trains of porpoises and dolphins (CP3- file). These events of positive detections are separated into quality classes. For the purpose of the present analysis only click trains classified as having a “High” and “Moderate” likelihood of being of porpoise or dolphin origin were used in order to keep the rate of false positive detections at a minimum. However, in order to verify whether detected click trains classified by the software as NBHF (narrow-band high frequency, indicating harbour porpoise) were indeed of porpoise origin, the raw data files (CP1-files) of the years 2009-2011 for all four stations were manually analysed to delete possible false positive detections (Gallus et al., 2012), e.g. boat or sonar wrongly classified as porpoise. Visual screening is time-consuming. Therefore the analysis of the data set of 2012 in this report represents only the results given by the software CPOD.exe. The software allows data to be exported from the train files in positive time units such as Detection Positive Minutes (DPM) or Detection Positive Hours (DPH), which were subsequently summed by day and averaged per month for both porpoises and dolphins.

Data from C-PODs at LS4 (Gubastuckaun) and LS2 (inner bay) from the years 2009, 2010 and 2011 were also re-analysed for positive detections of sonar (DPH/h) as an indicator of noise levels caused by boats in the study area. All classified (“high” and “moderate”) positive events were verified by manually checking the raw file, in order to ensure that false positive detections, such as NBHF, were eliminated from this data set.

The CPOD data of all four listening stations showed sonar frequencies which varied from 25 kHz to 160 kHz. The most frequently used sonar frequency in the years of 2009 to 2011 was 50 kHz. It is therefore likely that this frequency is used by local fishing boats.

Possible masking effects on harbour porpoise detections due to sonar frequencies around 130 kHz (i.e. the frequency used by echolocating harbour porpoises) or the sound exposure level cannot be completely ruled out. However, sonar frequencies around 130 kHz were only found at LS2 in the year 2009. The exposure sound level would only pose a problem due to high rates of following echoes, because the maximum resolution of click detection in C-PODs is 5µs. This scenario occurs only when vessels are very close to the C-PODs and was found only for a maximum of five minutes in the present dataset. In two hours, there were more than three different frequencies at the same time for more than five minutes. These hours were removed from the dataset due to possible masking effect.

2.3.3. Analysis The (manually checked and corrected) number of detection positive minutes per hour (DPM/h) for harbour porpoises at LS4 and LS2 for the years 2009-2011 was modelled against the explanatory variables tidal state (hours after high water), time of day (dawn, daylight, dusk and night), Julian day and presence / absence of (manually checked and corrected) boat sonar. Tidal information was obtained from Poltips V3.5 (http://www.pol.ac.uk/appl/poltips3.html), and sunset / sunrise times were downloaded from Neptune Tides (http://www.neptune- navigation.com). Both were linked to the mid-point of each hour (all in GMT) of acoustic data (i.e. XX:30h) in order to calculate hours after high water and hours before / after sunrise / sunset. Time of day was defined as follows: dawn = sunrise ± ½ hour, dusk = sunset ± ½ hour, daylight: > ½ hour after sunrise and > ½ hour before sunset, and night: > ½ hour after sunset and > ½ hour before sunrise.

Time of day and the presence or absence of boat sonar within each hour were included as nominal variables, and tidal state and Julian day as cyclic smoothers in a Generalized Additive Model (GAM; Hastie & Tibshirani, 1990) with a quasi-poisson error distribution. The response variable was harbour porpoise DPM/h. GAM’s have the advantage of letting the data dictate how the shape of the dependent variable is affected by each covariate by fitting non-parametric smoother terms. They have therefore been widely applied where the relationship between explanatory and dependent variables is not expected to be linear (e.g. Augustin et al., 1998; Bradshaw et al., 2004). Thin plate regression splines, implemented in the mgcv library (Wood, 2006) in the free statistics software R (R Development Core Team, 2006), were used as penalised regression smoothers for all models. The amount of smoothing was estimated using generalised cross-validation. However, the maximum degrees of freedom used for a single parameter was set to 4 in order to avoid over-fitting. Model selection was performed in a stepwise backward procedure by minimising the Generalised Cross-Validation (GCV) score (Wood, 2006). The GCV score is the mgcv equivalent to Akaike’s Information Criterion (AIC), which measures the goodness of fit of the model, penalised by the number of parameters included.

2.4. Photo-ID 2.4.1. Fieldwork The fieldwork protocol followed accepted standards for the photo-identification of bottlenose dolphins (for example, CCW (2005)). A group of dolphins was approached on a parallel course, matching the groups swimming speed, while closing to a distance of approximately 30m. Dorsal fin photos were then taken using a digital Canon EOS 40D camera with a 70- 200mm Sigma zoom lens (F2.8). Care was taken to keep the boat on as steady a speed and course as possible to make its movements more predictable for the animals. An encounter was ended when sufficient good-quality photographs had been obtained for photo-ID, or as soon as the group showed signs of an avoidance reaction to the boat (e.g. a noticeable change in dive patterns, consistently swimming away from the vessel, or diving underneath the boat and surfacing on the other side).

2.4.2. Analysis After download into a dated photo-ID folder on a PC, photographs were examined and light settings altered (if required) using the programs ‘Windows Picture and Fax Viewer’, ‘Microsoft Office Picture Manager’, and ‘Adobe Photoshop CS4’. All photos of sufficient quality for analysis were separated into ‘left side’ and ‘right side view’ folders. Within these, all photographs of the same individual were placed in a folder with a title containing a brief description of its main distinguishing features. For each individual, the best photograph was then selected and graded on its quality, based on the following grades:

Quality 1 – entire fin profile visible, in focus, at the correct angle, with good lighting;

Quality 2 – entire fin profile visible, slightly out of focus, at the correct (or close to) angle, with good to moderate light;

Quality 3 – entire fin profile visible, photo out of focus (possibly missing notch detail), close to the correct angle, with moderate to poor light;

Quality 4 – only part of fin visible, out of focus (possibly missing notch detail), close to the correct angle, with moderate to poor light / Or entire fin visible, but taken from a wrong angle, or fin masked by spray, and;

Quality 5 – not usable for photo-ID purposes: very dark/out of focus, only a small part of the fin visible due to masking by water or other animals

The ‘left’ and ‘right’ side view folders were then visually compared for matches. Photographs of an individual captured from both sides were placed in a single folder for that animal. All individuals photographed were then graded on the severity of their markings from 1 to 3 (Figure 3):

Grade 1 (well marked) - permanent, significant fin damage and deep healed wounds;

Grade 2 (slightly marked) - minor fin damage and deep scratches, including rake marks;

Grade 3 (recognisable from one side only) - superficial scratches, which are quickly lost through healing or are obscured through the acquisition of further scarring.

a) b) c)

Figure 3. Examples of Grade 1 (a), Grade 2 (b), and Grade 3 (c) fin markings.

The best photos of each individual were compared with the current Broadhaven 2002 – present bottlenose dolphin catalogue. Individuals which could not be matched to the catalogue (i.e. not captured before), but with a grade 1 or 2 dorsal fin and a quality 1-3 photograph were given a unique ID number and placed into the catalogue. Original folders for that encounter were then re-named using each individual’s ID number. Details of the encounter such as ‘sighting ID’, date, ID numbers of individuals seen, marking grade, side photographed (Left/Right/Both), ID-number of best photograph (left and right), photograph quality, name of photographer and any other additional notes were recorded in an Excel database. Finally, a re-sightings database containing ID numbers, marking grades and dates of re-captures was also updated with the most recent date of any re-captures or date of new individuals (new ID numbers) added to the catalogue along with quality of the best photograph(s) for the most recent encounter.

3. RESULTS

3.1. Visual effort Sightings on the offshore line-transect survey (May 29th 2012) included minke whale, Risso’s dolphin, common dolphin, white beaked dolphin and unidentified seals. No species were seen in the offshore area which did not occur within Broadhaven Bay (Figure 4).

Figure 4. Sightings of all marine mammals during the line-transect survey in 2012.

Land-based watches from Gubastuckaun and Doonanierin Point were conducted on 45 days (238 scans in good viewing conditions) in total between January and November 2012. No fieldwork could be carried out in March, September and December due to adverse weather conditions. Effort was highest during the months of June (n = 9 days; 67 scans) and July (n=10 days; 55 scans) (Figure 5a & 5b).

Unlike the previous two years when grey seal was the most commonly recorded species (Anderwald et al., 2012), the common dolphin was the most frequently observed species in 2012. The overall number of grey seal sightings (not corrected for effort) declined for the second consecutive year, i.e. 67% fewer sightings than 2011and 82% fewer sightings than 2010. Common dolphins also accounted for the highest number of individuals (with group sizes of up to 125 animals), but the number of sightings was 50% lower than in 2011. Minke whale sightings declined by 75% compared to 2011, however the number of sightings in 2011 were 64% higher than in previous years. The number of bottlenose dolphin sightings in 2012 remained similar to 2011, with both years showing half the number of sightings recorded in 2010. Confirmed harbour seal sightings also declined in 2012, making up 2% of all seal sightings, compared with 6% of seal sightings in 2011 (Table 1).

All species which had previously been recorded in Broadhaven Bay were also sighted in 2012 except for sei whale (Balaenoptera borealis), seen in 2009, Atlantic white sided dolphin (Lagenorhynchus acutus) and killer whale (Orcinus orca) the latter two species were last seen in 2011.

Figure 5a. Monthly effort of cliff-based observations for each year expressed as the total number of days per month (n=337).

Figure 5b. Monthly effort of cliff-based observations for each year, expressed as the total number of scans per month (n=1628).

Table 1. Summaries of all sightings for 2012, including cliff-based effort-related, opportunistic and vessel- based sightings. Black-shaded fields indicate presence of the species for that month in 2012; grey-shaded fields indicate that the species was not observed in 2012, but was present in the study area of Broadhaven Bay during that month in a previous year of the monitoring programme. Effort during December was low (4 scans in 2008 only; (see Figure 5), therefore December was omitted.

No. No. Group size Seasonal presence sight’s ind.’s 2012 2012 2012 Min Max J F M A M J J A S O N Cetaceans Minke whale 9 9 1 1

Sei whale 0 0 - -

Killer whale 0 0 - -

Bottlenose 12 173 1 40 dolphin Common 19 1195 2 125 dolphin Risso’s 5 17 1 8 dolphin White-beaked 1 3 3 3 dolphin Atlantic white- 0 0 - - sided dolphin Harbour 7 15 1 3 porpoise Unidentified 17 270 1 75 dolphin Unidentified 0 0 - - whale Unidentified 0 0 - - cetacean

Seals Grey seal 16 19 1 3

Harbour seal 1 1 1 1

Unidentified 35 41 1 5 seal

Other species Otter 0 0 - -

Basking 10 11 1 2 shark Sunfish 0 0 - -

Leatherback 0 0 - - turtle

3.1.1. Seasonal occurrence Taking into account all years of monitoring effort in Broadhaven Bay to date, minke whale, bottlenose and common dolphins, harbour porpoise and grey seal all show year-round presence in the study area (Table 1), although seasonal differences in sighting rates exist (Figure 6). By contrast, sightings of Risso’s dolphins are confined to the summer months (Table 1). Although confirmed sightings of harbour seals so far only exist between March and September, some unidentified seals may have accounted for this species also during winter, especially considering the difficulty in distinguishing harbour from young grey seals at a distance.

Although basking sharks typically migrate to these latitudes in the summer, the species has now been observed in Broadhaven Bay in every month between March and October. Sunfish sightings have been confined to summer and autumn, and leatherback turtle records to late summer and autumn months only (Table 1).

Minke whales have been recorded most frequently in the study area between May and November, but sighting rates peaked during October and November for the years 2009 to 2012 (Figure 6a & 6b).

Bottlenose dolphin occurrence in Broadhaven Bay has followed no clear seasonal pattern in any year of observations (Figure 6c & 6d). By contrast, common dolphin presence has peaked during autumn and winter, particularly in years with higher sighting rates (Figure 6e & 6f), although there was no autumn peak in 2012.

Grey seals were present during every month in which observations took place during 2012, contrasting with 2011 during which there were four months without any sightings. The peak in sighting rate during February was also seen in 2011 (Figure 6g & 6h).

There were too few sightings of harbour seals in 2012 to establish a seasonal pattern in occurrence. However, data from all years combined show peaks in sighting rates during June and September (Figure 6i & 6j).

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Figure 6a. Seasonal occurrence of minke whales in Broadhaven Bay, expressed as proportion of scans in which the species was present, for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort.

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Figure 6b. Seasonal occurrence of minke whales in Broadhaven Bay, expressed as the average number of individuals per scan, for each year of the monitoring programme. Broken lines represent months with no cliff- based visual effort.

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Figure 6c. Seasonal occurrence of bottlenose dolphin in Broadhaven Bay, expressed as proportion of scans in which the species was present, for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort.

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Figure 6d. Seasonal occurrence of bottlenose dolphins in Broadhaven Bay, expressed as the average number of individuals per scan, for each year of the monitoring programme. Broken lines represent months with no cliff- based visual effort.

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Figure 6e. Seasonal occurrence of common dolphins in Broadhaven Bay, expressed as proportion of scans in which the species was present, for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort.

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Figure 6f. Seasonal occurrence of common dolphins in Broadhaven Bay, expressed as the average number of individuals per scan, for each year of the monitoring programme. Broken lines represent months with no cliff- based visual effort.

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Figure 6g. Seasonal occurrence of grey seals in Broadhaven Bay, expressed as proportion of scans in which the species was present, for each year of the monitoring programme. Broken lines represent months with no cliff- based visual effort.

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Figure 6h. Seasonal occurrence of grey seals in Broadhaven Bay, expressed as the average number of individuals per scan, for each year of the monitoring programme. Broken lines represent months with no cliff- based visual effort.

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Figure 6i. Seasonal occurrence of harbour seals in Broadhaven Bay, expressed as proportion of scans in which the species was present, for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort.

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Figure 6j. Seasonal occurrence of harbour seals in Broadhaven Bay, expressed as the average number of individuals per scan, for each year of the monitoring programme. Broken lines represent months with no cliff- based visual effort.

3.1.2. Models of temporal occurrence

Exploratory analysis on the effects of different categories of survey / construction activities on the daily presence of the five most frequently recorded marine mammal species in Broadhaven Bay indicated that ‘any survey / construction activity’ (i.e. all categories combined) was likely to influence marine mammal occurrence (no significance implied) and should therefore be included in the models. For common dolphin, grey and harbour seals, ‘acoustic survey’ and ‘survey general’ (i.e. including both acoustic and ROV surveys) also appeared to have an effect. For these three species, the first run of each model therefore included ‘any survey / construction activity’, and once an optimal model was found, this category was replaced with ‘acoustic survey only’ and ‘surveys general’ in a second and third run, respectively. By contrast, the models for bottlenose dolphin and minke whale were run only once with ‘any survey / construction activity’ as explanatory variables.

When corrected for yearly and seasonal fluctuations, environmental parameters (SST, SST gradient and tidal range) and variables influencing sighting efficiency and effort (sea state and number of scans /day, respectively) in the logistic regressions, the presence of survey / construction activities did not influence the daily occurrence of any of the five species. This result did not change when this parameter was replaced with ‘survey general’ or ‘acoustic survey’ in the models for common dolphin, grey and harbour seals. By contrast, the occurrence of all five species was affected by the factor Year (significant in all models) and detection probability (i.e. effort and/or sea state; Table 2, Figure 7).

Minke whale and common dolphin occurrence declined in 2012 (Figures 7a and c), bottlenose dolphin, grey and harbour seal presence was significantly lower in 2012 by comparison to 2002 (Figures 7b, d and e). Parallels were apparent between the occurrence of grey and harbour seals.

Bottlenose and common dolphin occurrence show a significant seasonal pattern between June and September, with bottlenose dolphins occurring more frequently earlier in the season, and common dolphins later (Figures 7b and c). Such a seasonal difference was absent in minke whale, grey and harbour seal.

SST and SST gradient played no role in determining the occurrence of any of the five species. However, tidal range was significant in the final model for harbour seal, with animals occurring more frequently in Broadhaven Bay during spring than neap tides (Figure 7e).

As expected, at least one parameter correcting for sighting efficiency (i.e. sea state and/or number of scans per day) was significant in four of the five models (Table 2, Figure 7). Sea state has a less significant effect on the sightability of bottlenose dolphins, which may be explained by their often conspicuous surface behaviour, combined with a preferred usage of Rossport Bay which is generally calmer than other parts of Broadhaven Bay.

Table 2. Final logistic regression models for daily presence / absence of the five most frequently observed marine mammal species in Broadhaven Bay. df = degrees of freedom.

a) Minke whale

Parameters included df Deviance AIC Likelihood ratio p- value Year & Sea state & Mean no. scans 131.84 149.84 Year 6 158.27 164.27 26.43 <0.001 Sea state 1 139.96 155.96 8.12 0.004 Mean no. scans 1 142.57 158.57 10.73 <0.001

b) Bottlenose dolphin

Parameters included df Deviance AIC Likelihood ratio p- value Year & Julian day 184.63 202.63 Year 6 201.04 207.04 16.42 0.012 Julian day 1 190.17 206.17 5.54 0.018 Sea state 1 189.24 205.24 4.62 0.032

c) Common dolphin

Parameters included df Deviance AIC Likelihood ratio p- value Year & Julian day & Sea state 145.25 163.25 Year 6 172.38 178.38 27.13 <0.001 Julian day 1 158.66 174.66 13.41 <0.001 Sea state 1 159.21 175.21 13.96 <0.001

d) Grey seal

Parameters included df Deviance AIC Likelihood ratio p- value Year & Sea state & Mean no. scans 203.26 221.26 Year 6 246.41 252.41 43.15 <0.001 Sea state 1 210.53 226.53 7.28 0.007 Mean no. scans 1 221.23 237.23 17.98 <0.001

e) Harbour seal

Parameters included df Deviance AIC Likelihood ratio p- value Year & Tidal range & Mean no. 128.18 146.18 scans Year 6 167.38 173.38 39.2 <0.001 Tidal range 1 134.71 150.71 6.53 0.011 Mean no. scans 1 139.74 155.74 11.56 <0.001

a) Minke whale

b) Bottlenose dolphin

c) Common dolphin

d) Grey seal

e) Harbour seal

Figure 7. Parameters included in final logistic regression models for presence / absence of each of the five most frequently recorded species. Asterisks in histograms for Year denote significance relative to the year 2002 (used as reference level): *0.05, **0.01, ***0.001. Boxplots show median value, interquartile range (height of box) and 1.5 x interquartile range (whiskers); outliers are represented by circles.

3.1.3. Spatial distribution The spatial distribution of marine mammal sightings in Broadhaven Bay during 2012 followed largely the same pattern as observed in previous years of the monitoring programme.

The tidally active area around Erris Head appears of particular importance for a variety of species including minke whale, common dolphin, harbour porpoise, Risso’s dolphin, harbour seal, basking shark and sunfish, although no sunfish were seen in 2012 (Figures 8a,c,d,e,h,j).

As in previous years, minke whales and common dolphin sightings were concentrated predominantly in the outer (in line with Gubastuckaun and Doonanierin Point and outward) and western part of the bay, particularly around Erris Head, based on both distribution of first sightings (Figures 8a,c) and tracks of individuals or groups (Figures 9a,c). Risso’s dolphins, although represented by only a small number of sightings since 2002, have not been observed

in the inner part of Broadhaven Bay, although the species has occurred close to shore around Erris Head (Figure 8e). Interestingly, bottlenose dolphin, harbour porpoise, grey and harbour seal showed a more inshore distribution, with almost all sightings occurring within the boundaries of the cSAC (Figures 8b,d,g,h). The preference for waters close to the coast is particularly evident from the tracks of individual bottlenose dolphin groups, although several groups in 2012 were tracked outside the SAC boundary (Figure 9b). However, a potential bias towards a greater number of sightings closer to the two land-based observation sites is suspected for harbour porpoise, grey and common seals, i.e. the least conspicuous species (Figure 8e). Plots of all other species appear to reflect their real distribution patterns within Broadhaven Bay, as indicated by the lack of difference in the distribution of land- and boat- based sightings. As expected, the frequency of recording unidentified species increased with increasing distance from the two land-based observation sites, although during 2012 no large unidentified cetaceans were recorded (Figure 8f).

Figure 8a. Minke whale. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8b. Bottlenose dolphin. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8c. Common dolphin. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8d. Harbour porpoise. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8e. Other cetacean species

Figure 8f. Unidentified cetaceans.

Figure 8g. Grey seal. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8h. Harbour seal. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8i. Unidentified seals. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11). Circles = sightings from cliff; squares = sightings from boat.

Figure 8j. Other species. Red symbols = sightings from 2012; black symbols = sightings from previous years (2002, 2005, 2008-11).

Figure 8(a-j). Spatial distribution of marine mammal sightings. Only first sightings for which accurate positions were available (i.e. theodolite or GPS reading) are included. Green stars represent the land-based observation sites.

Figure 9a. Minke whales. Red lines represent tracks from 2012, blue lines from earlier years of the monitoring programme.

Figure 9b. Bottlenose dolphins. Red lines represent tracks from 2012, blue lines from earlier years of the monitoring programme.

Figure 9c. Common dolphins. Red lines represent tracks from 2012, blue lines from earlier years of the monitoring programme.

Figure 9(a-c). Theodolite tracks of a) individual minke whales and groups of b) bottlenose and c) common dolphins from cliff-based observations.

Based on the results of the classification tree, depth was the most important parameter in spatially separating the five most frequently recorded species within Broadhaven Bay, followed by distance from the tidally active area at Gubastuckaun. By contrast, slope played no role in spatially separating the species. The optimal tree size determined by cross- validation was three (Figure 10), including both depth and distance to Gubastuckaun (Figure 11). This tree had an error of 71.5% of the root node error (i.e. classification error with no splits). However, the only successful differentiation was between bottlenose dolphins (74% of data points correctly classified) and common dolphins (91% correctly classified), and bottlenose dolphins and minke whales (86% classified as common dolphins), respectively, based on their different depth preferences (bottlenose dolphins predominantly at <30m, and common dolphins and minke whales at >30m). 54% of harbour seal sightings appeared in a third category (named ‘grey seal’ by the software because this was the most numerous species in this cluster) which could be distinguished from the category dominated by bottlenose dolphin by its closer proximity to the tidally active area around Erris Head. Grey seals appeared equally frequently in all three categories (Figure 11).

Figure 10. Determination of optimal tree size. The y-axis represents the relative error of the predictions calculated by cross-validation; cp stands for the complexity parameter of the tree. Corresponding tree sizes (i.e. the number of splits plus 1) are indicated along the top. The horizontal dotted line represents the mean error plus standard deviation of the cross-validations at convergence. According to the one standard deviation rule, the optimal tree size is at the cp for which the first mean error lies below the line, i.e. at cp=0.035 with a corresponding tree size of 3.

Figure 11. Optimal classification tree of species according to spatial distribution. Conditions indicated at the top of each split apply to the left-hand branch. The unit for both depth and distance is metres. Figures at the bottom of each branch refer to the number of data points for each species classified as the dominant species of that branch. From left to right, these are: bottlenose dolphin, common dolphin, harbour seal, grey seal and minke whale. BD = bottlenose dolphin, GS = grey seal, CD = common dolphin.

3.2. Acoustic effort A total of 23,784 hours of acoustic data were obtained from C-PODs between January and mid December 2012, by comparison to 21,336 hours in 2011, 19,896 hours in 2010 and 16,992 hours in 2009. All PODs performed well throughout deployment periods, except for some loss of data due to internal C-POD malfunction at LS4 off Gubastuckaun during July 2010 and at LS2 in the inner bay in February 2011 (Figure 12a-c).

2009 2010

2011 2012

Figure 12a. Total monthly effort (days) for LS1 positioned at Rossport North.

2010

2011 2012

Figure 12b. Total monthly effort (days) for LS2 positioned at Rossport Central.

2009 2010

2011 2012

Figure 12c. Total monthly effort (days) for LS3 positioned at Rossport South.

2009 2010

2011 2012

Figure 12d. Total monthly effort (days) for LS4 positioned at Gubastuckaun (See Figure 1).

Detection rates for both harbour porpoises and dolphin species were lowest in the northern part of Rossport Bay (LS1) and highest off Gubastuckaun (LS4). This spatial difference was consistent throughout the period of acoustic monitoring (Figures 13 & 14). Both harbour porpoises and dolphin species showed year-round presence in Broadhaven Bay. Detection rates for harbour porpoises peaked during winter and were lowest during summer / autumn. This seasonal pattern was largely consistent between years, and between inner and outer bay (Figure 13). By contrast, detection rates for dolphin spp. in the inner bay (probably mostly reflecting bottlenose dolphins based on their spatial distribution; see Figures 8 & 9) were higher in spring and summer from 2010 to 2011, while no particular seasonal pattern was apparent at Gubastuckaun in the outer bay (reflecting a variety of species, but likely consisting predominantly of common dolphin detections; Figure 14).

The final GAMs for harbour porpoise detection rates at LS4 (Gubastuckaun) and LS2 (Rossport centre) during 2009-2011 included the parameters Julian day, time of day and

presence / absence of boat sonar (Table 3, 4 and Figure 15, 16). At both positions a peak in harbour porpoise DPM/h occurred during winter, whereas autumn yielded the lowest detection rates (Figure 15a and 16a). Harbour porpoise DPM/h were also higher at night and dawn by comparison to daylight (Table 3 and 4, Figure 15b and 16b). While detection rates at LS4 were significantly lower at dusk than during the day, there was no difference between the two periods at LS2. Detection rates also showed a significant negative relationship with the presence of boat sonar at both listening stations (Table 3 and 4, Figure 15c and 16c). The final models explained 11.2% and 20.5% of the deviance at LS4 and LS2, respectively. The state of the tidal cycle had no influence on porpoise DPM/h and was not included in the final model.

Figure 13. Monthly average Detection Positive Hours per day of harbour porpoise during the years 2009 – 2012, using passive acoustic monitoring (C-PODs). Months without coverage for a particular listening station (LS) are indicated by a square in the colour of that listening station. Detections classified by the software as NBHF (indicating harbour porpoise) of the years 2009-2011 have been verified by visual screening to eliminate false-positive detections.

Figure 14. Monthly average Detection Positive Hours per day for dolphin spp. during the years 2009 - 2012 of, using passive acoustic monitoring (C-PODs). Months without coverage for a particular listening station (LS) are indicated by a square in the colour of that listening station.

Table 3. Summary for final model of harbour porpoise detection positive minutes per hour (DPM/h) for LS4. df = degrees of freedom, p = significance of parameter. N = 18’938.

Parametric coefficients Estimate t-value p ± std. error Intercept 0.192 ± 0.024 8.106 <0.001

Time of day Dawn vs. Day 0.202 ± 0.065 3.107 <0.001 Dusk vs. Day -0.631 ± 0.099 -6.356 <0.001 Night vs. Day 0.175 ± 0.029 5.897 <0.001

Sonar presence vs. absence -0.561 ± 0.124 -4.524 <0.001

Smooth terms df F p s(Julian.day) 2.98 605 <0.001

a) Julian day

b) Time of day c) Boat sonar Figure 15. Results of Generalised Additive Model for harbour porpoise detection rates at LS4 (Gubastuckaun) between July 2009 and December 2011. The final model included the smoother Julian day (a) and the two nominal variables Time of day (b) and presence / absence of boat sonar (c).

Table 4. Summary for final model of harbour porpoise detection positive minutes per hour (DPM/h) for LS2. df = degrees of freedom, p = significance of parameter. N = 16’313.

Parametric coefficients Estimate t-value p ± std. error Intercept -2.413 ± 0.045 -53.484 <0.001

Time of day Dawn vs. Day 0.603 ± 0.087 6.962 <0.001 Dusk vs. Day 0.075 ± 0.111 0.676 0.499 Night vs. Day 0.519 ± 0.486 11.907 <0.001

Sonar presence vs. absence -2.717 ± 0.487 -5.581 <0.001

Smooth terms df F p s(Julian.day) 2.97 801 <0.001

a) Julian day

b) Time of day c) Boat sonar Figure 16. Results of Generalised Additive Model for harbour porpoise detection rates at LS2 (Rossport centre) between July 2009 and December 2011. The final model included the smoother Julian day (a) and the two nominal variables Time of day (b) and presence / absence of boat sonar (c).

3.3. Photo-ID Four bottlenose dolphin photo-ID encounters were carried out within the study area in 2012, bringing the total number to date to 30 encounters (from 2008 to 2012). The photo-ID catalogue for Broadhaven Bay currently contains 185 individuals: 64 well-marked (Grade 1), 52 slightly marked (Grade 2), 46 left only and 44 right only (Grade 3).

36% of animals were photographed in only one encounter. This included individuals sighted in 2002, which after a six year gap in photo-ID effort could not be matched to animals photographed in more recent years. However, the re-sighting rate was high between 2008 and 2011, with individuals seen up to 12 times. Including 2011 with a lower re-sighting rate, 64.5% of all animals were seen at least twice within Broadhaven Bay over the entire monitoring period (Figure 16). The high re-sighting rate of 74% since 2008 (Figure 17) indicates a relatively high degree of site fidelity (including long-term), especially considering the small size of the study area.

After steep increases in the discovery curve (i.e. the number of new individuals added to the catalogue) during 2009 and 2010, few new animals have been encountered during 2011 and 2012 (Figure 18). However, this may be partly due to the lower number of photo-ID encounters (n=3) by comparison to 2009 (n=7) and 2010 (n=10).

Comparisons have been made with photo-ID catalogues of bottlenose dolphins held elsewhere in Ireland as well as in adjacent regions of the UK. These have yielded: - 48 matches with the Irish Coastal Bottlenose Dolphin catalogue (containing images owned by the Irish Whale and Dolphin Group (IWDG) and Galway-Mayo Institute of Technology (GMIT) of individuals from Galway Bay and Donegal Bay, - 26 matches with the University College Cork catalogue containing animals from Connemara and other locations along the west coast of Ireland, - one match with an individual photographed in Killiney Bay, Co. Dublin (contained in the IWDG online catalogue; www.iwdg.ie/photoid), and - a group of five individuals from the Moray Firth, Scotland, which have also been seen in the Hebrides (Robinson et al., in press).

However, there have been no matches between Broadhaven Bay and the Shannon Estuary (photographs compared with both the Irish Coastal Bottlenose Dolphin and UCC catalogues), nor with the Sea Watch Foundation (http://seawatchfoundation.org.uk) catalogue containing ca. 400 individuals from the Irish Sea.

Figure 16. Number of encounters in which individual bottlenose dolphins (expressed in percentages) have been re-sighted within Broadhaven Bay since the beginning of the monitoring project.

Figure 17. The number of re-sightings of individual bottlenose dolphins in photo-ID encounters from 2008 to 2012.

Figure 18. Discovery curve for bottlenose dolphins photographed in Broadhaven Bay, including marked (well- and slightly-marked) individuals only. Data from 2002 are not shown due to the long gap in photo-ID effort.

4. DISCUSSION

The high importance of Broadhaven Bay as a marine mammal habitat continues to be reflected by the high species diversity (6 species of cetacean and two seal species were recorded in 2012), high sighting rates and year-round presence of some species, the regular presence of juvenile cetaceans and seals and cetacean calves, and high frequencies of feeding activity recorded within the study area. The year-round monitoring effort since 2008/09 has provided new insights for the area into the winter occurrence and effort-corrected sighting frequencies particularly of minke whale, bottlenose and common dolphins, and grey seal, which were all present in Broadhaven Bay throughout the year. As observed elsewhere in Ireland, highest common dolphin sighting rates occurred from September to February (Goold J.C. 1998, Berrow et al., 2012).

4.1. Spatial distribution The total number of sightings for minke whale, bottlenose and common dolphins, grey and harbour seals, combined with tracks of individuals or groups of minke whales, bottlenose and common dolphins, has enabled an investigation into the fine-scale spatial use of the study area by these species. Both minke whales and common dolphins used mainly the outer and western parts of Broadhaven Bay, while bottlenose dolphins generally preferred Rossport Bay and the inner part of Broadhaven. Harbour seals were distributed mainly around Erris Head with some sightings within Rossport Bay and in the innermost part of Broadhaven Bay, while grey seals were widely distributed throughout the study area. This spatial pattern was reflected in the classification tree of the five species based on depth, slope and distance from the tidally active area around Erris Head. Only common and bottlenose dolphins, and minke whales and bottlenose dolphins could be successfully distinguished from each other by depth, while approximately half the harbour seal sightings formed a third category, distinguished from bottlenose dolphins by a closer proximity to Erris Head, and grey seal sightings were distributed equally across all three categories. This suggests differential habitat use of the study area by bottlenose and common dolphins, possibly reflecting differences in local key prey species (although both species are opportunistic feeders (e.g. Berrow & Rogan, 1995; Hernandez-Milan & Rogan, 2010)), and a relatively wide niche width for grey seals.

Grey and harbour seals could not be successfully distinguished from each other spatially, but grey seals are far more numerous in the study area than harbour seals, possibly due to the proximity of the Inishkea Islands which represent the largest breeding and moulting colony of grey seals in Ireland (Ó Cadhla et al., 2007). Both species have a relatively opportunistic diet, and it is likely that there will be overlap between them in their prey species (e.g. gadoids, sandeels and flatfish; Payne & Selzer, 1989; Strong, 1996; Hammond & Grellier, 2006; Hammond & Harris, 2006; Cronin et al., 2008). It is unclear if resource competition between the two species exists within the study area.

The second species pair which could not be distinguished spatially from each other was common dolphin and minke whale. Both species have on occasion been seen feeding on bait balls of pelagic fish (with gannets associated) off Erris Head in close proximity to each other, i.e. probably taking the same prey at the time (most likely shoaling sprat, herring or mackerel). In inshore Irish waters, Trisopterus spp. appears to form an important part of the diet of common dolphins (Brophy et al., 2008). Minke whale diet off western Ireland is unknown, but off Scotland, the species feeds primarily on clupeids and sandeels (Pierce et al., 2004), making it likely that similar prey is taken off the west coast of Ireland.

4.2. Temporal patterns of harbour porpoise occurrence (acoustic detections) The temporal occurrence of harbour porpoises off Gubastuckaun and Rossport Bay based on C-POD detections showed clear seasonal and daily patterns, but was independent of the tidal cycle. Both the seasonal peak in detections during winter and the daily pattern with highest detection rates at night (and dawn) were consistent with findings from Cardigan Bay (Simon et al. 2010). Simon et al. interpreted their results as the possibility of harbour porpoises avoiding violent interactions with bottlenose dolphins, which showed reverse seasonal and daily patterns of occurrence. It is not clear to what extent violent interactions with bottlenose dolphins pose a risk to harbour porpoises on the west coast of Ireland, where bottlenose dolphin density is lower than in Cardigan Bay. It is also possible that higher echolocation activity at night is due to feeding activity, harbour porpoises have shown higher click activity at night and more frequent dive rates (Berrow et al., 2009). While increased echolocation would seem to compensate for the loss of light, DeRuiter et al. (2009) found that illumination level did not affect click rate, suggesting any diel variation is influenced by factors other than light level. The daily pattern of feeding activity can be investigated further by specifically

analysing click trains associated with feeding from the POD data, and this is planned as part of the on-going acoustic monitoring effort within Broadhaven Bay. The significant negative relationship between harbour porpoise detection rates and the presence of boat sonar suggests avoidance of boats by the species. This result is consistent with the negative relationship between harbour porpoise detection rates within Rossport Bay and numbers of boats counted over the entire study area during cliff-based observations during 2009 and 2010 (Coleman, 2011). An apparent lack of (short-term) avoidance behaviour to construction activity by the visually better detectable delphinids (see above) suggests substantial differences between harbour porpoise and other odontocetes. Harbour porpoise produce high-frequency, narrowband signals (clicks) to locate their prey, for navigation (Verfuß and Schnitzler 2002, Verfuß et al., 2009) and spatial orientation (Verfuß et al 2005). Furthermore, Clausen et al. (2010) provide evidence that the harbour porpoise communicates acoustically using specific patterns of clicks with source properties comparable to normal echolocation clicks. Their hearing ranges from 250 Hz to 160 kHz with a maximum sensitivity between 100 to 140 kHz (about 33 dB re 1 μPa) (Kastelein et al., 2002) correspond with the frequency range of their echolocation clicks from 125·kHz to 148·kHz (Møhl and Andersen, 1973; Goodson and Sturtivant, 1996; Villadsgaard et al. 2007). It is therefore likely that sonar frequencies which were recorded within the bay and varied from 25 kHz to 160 kHz would have a greater negative impact on harbour porpoise compared to other odontocetes. It would also be consistent with suggestions in the literature that harbour porpoises tend to be more sensitive to anthropogenic noise than other odontocetes due to anatomical differences in the inner ear (Ketten, 2000; Lucke et al., 2009). Sensitivity is likely to vary between different sonar frequencies, but these could not be investigated separately due to low sample sizes.

4.3. Bottlenose dolphin photo-ID Results from photo-identification of bottlenose dolphins confirm the importance of Broadhaven Bay for the species. Although not as frequently sighted as common dolphins during 2010, 2011 and 2012, a minimum of 185 animals have used the study area since autumn 2008 (with Rossport Bay representing a particularly important area), and individuals have returned regularly (up to 11 times) during a three year period.

Results from comparisons with other photo-ID catalogues for the species are consistent with ranging patterns published previously for this population: O’Brien et al. (2009) documented distances of up to 650km between sighting locations of the same individuals from the west coast population of Ireland, indicating that the animals visiting Broadhaven Bay are highly mobile and range over a wide area. However, as in the present study, no matches were found between west coast animals and the Shannon population, but one match was found with an animal off Co. Dublin in 2012. These findings are also consistent with genetic evidence of distinct bottlenose dolphin populations in Irish waters (Mirimin et al., 2011): although based on a small sample size (n=14, with only 3 individuals sampled in Broadhaven), bottlenose dolphins sampled in Connemara and Mayo form a cluster which shows significant genetic differentiation from animals in the Shannon population. Unfortunately, insufficient tissue samples are available from the Irish Sea to enable a genetic comparison with that population.

4.4. Effects of construction Over the short term (i.e. the same day), no negative effect of construction-related activities within Broadhaven Bay could be determined for any of the five most frequently recorded species, indicated by the absence of significant effects of construction on species occurrence in all models. However, all species showed inter-annual differences in occurrence, and the three coastal species (bottlenose dolphin, grey and harbour seals) showed parallels in their sighting rates between different years of construction activity, which suggested a common cause for their temporary declines during 2005, 2008 and 2009 by comparison to 2002 (Anderwald et al., 2011). Despite the absence of significant short-term effects (on the scale of a few days), this could be interpreted as a long-term effect of construction-related disturbance, i.e. affecting the occurrence of these three inshore species over the entire monitoring period. On the other hand, the inter-annual patterns in occurrence were not consistent with the relative intensity of construction: sighting rates of all three species were lowest in 2008, but the highest levels of construction activity occurred during 2009. Inclusion of the visual data collected during 2011 and 2012 (two consecutive years without anthropogenic disturbance in the bay), also suggest reasons other than construction activity alone for the inter-annual fluctuations (see below). Occurrence of the five main species declined in 2012, indeed sighting rates were comparable with 2008/09 levels, with sighting rates for both seal species particularly low.

The distribution of marine mammals is influenced by a variety of factors, but primarily their prey. Small shifts in the distribution of key prey species will result in distributional changes of their predators, and these can only be tracked if the study area is sufficiently large. Since no construction activity took place during 2011 and 2012, it is most likely that the changes in occurrence of all five species over those two years had a natural cause such as distributional changes of their prey rather than anthropogenic disturbance. Nevertheless, the role of construction activities in the decline of all three inshore species during 2005, 2008 and 2009 can only be determined once a longer data series of sighting rates in years without anthropogenic disturbance becomes available.

4.4.1. Anthropogenic impacts. monitoring considerations Ideally, monitoring projects with the aim of determining the presence and severity of anthropogenic impacts on natural systems follow a BACI design (Before – After Control – Impact). The present project has been constrained by the lack of a monitoring period before construction activity within Broadhaven Bay commenced in 2002. Although a pilot study was conducted during October and November 2001, this was too short, being outside both the main fieldwork season (i.e. when weather conditions allow the highest levels of observer effort) and the main period of construction activities during subsequent years (May – September), and it did not include monitoring of seals, so it could not be used as a baseline. Instead, the 2002 season, during which survey / construction works for the pipeline were already underway, had to be used as the reference level in this study. Although offshore construction activity occurred at relatively low levels in 2002 and 2005, data collected during those years unfortunately cannot be considered as monitoring of an undisturbed system.

Since the study area is very small in relation to the mobility of marine mammals, it would also have been useful not only to have a spatially separate undisturbed control site with environmental characteristics as similar as possible to Broadhaven Bay, but also for the offshore area to be monitored throughout the duration of the project in order to establish the importance of the bay as a marine mammal habitat relative to the wider area. A control site was lacking, and although offshore transects were carried out in 2011 and 2012, it has proven difficult to achieve a consistent survey effort due to the prevailing high winds and sea state.

In addition to the lack of baseline monitoring and a control site, establishing the importance of short-term effects of the construction activities and (natural) year to year variation in the

occurrence of different species within Broadhaven Bay has been made difficult by the gaps in coverage during years when no construction activity took place (i.e. 2003, 2004, 2006 and 2007), and the different start periods of monitoring during 2002, 2005 and 2008. It is now possible to partly address the former issue in the analysis by the monitoring effort conducted during 2011 and 2012 (both years without construction activity). However, the different start times in three years of the monitoring programme have reduced the comparable visual datasets available (and thus the sample size and statistical power) to only four months per year (June to September) for 2002, 2005 and 2008-2012, making it difficult to investigate the effects of construction works. To undertake this in a statistically robust manner, the same time period needs to be compared between years to take account of natural seasonal patterns in the occurrence of marine mammals; the study area is likely to be used differently by different species during the breeding season vs. the rest of the year. Minke whales, for example, breed during winter, during which season the majority of the population appears to migrate further offshore and possibly into lower latitudes (Anderwald, 2009). By contrast, the main breeding season of the smaller odontocetes in the Eastern North Atlantic is between April and September, as is that of harbour seals, while grey seals breed during late autumn and winter (Evans & Stirling, 2001). Year-round observer effort, including during years when no anthropogenic disturbance is present, is therefore important in understanding seasonal variation in the use of the study area by different species and to help explain possible differences in sensitivity to construction-related impacts

ACKNOWLEDGEMENTS

The present monitoring programme has been funded by Shell E&P Ireland Ltd. Our thanks go to all past observers on the project for their valuable contribution in collecting and processing field data, as well as the numerous people who have supported the project locally, have helped out with logistics and material, or reported sightings: Anthony Irwin, Machiel Oudejans, Vincent and Simon Sweeney, Anneli Englund and our skippers Gerry and Edward Reilly. We particularly want to acknowledge Padraig O’Donnell for his invaluable help with the deployment and servicing of the POD’s, making the moorings for us, and being prepared to share his extensive local knowledge with us to select the safest mooring locations. We would also like to thank our office colleague Gemma O’Connor, who readily provided her computer expertise whenever needed.

Nick Tregenza not only provided a C-POD on loan for the project, but also greatly helped us with technical advice on the use of the acoustic equipment.

The Broadhaven Bay bottlenose dolphin photo-ID catalogue was reciprocally exchanged with catalogues held by the Irish Whale and Dolphin Group (Dr. Joanne O’Brien), the School of Biological, Earth and Environmental Sciences, University College Cork (Anneli Englund) and the Sea Watch Foundation (Daphna Feingold). We are very grateful for their cooperation in shedding light on the wider-scale movement patterns of bottlenose dolphins photographed within Broadhaven Bay.

Finally, we would like to thank Eamon Reilly and other local land-owners for allowing the team to access their land in order to conduct the cliff-based observations from Gubastuckaun and Doonanierin Point.

Background maps on pages 10 and 46 to 52 © Crown Copyright and/or database rights. Reproduced by permission of the Controller of Her Majesty’s Stationary Office and the UK Hydrographic Office (www.ukho.gov.uk).

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