Marine Mammal Monitoring in Broadhaven Bay 2010

Transcription

1 Marine Mammal Monitoring in Broadhaven Bay 2010 Progress Report to RSK Environment Ltd. July 2011 Coastal and Marine Research Centre Environmental Research Institute University College Cork Ireland EPA Export :23:35:14

2 Marine Mammal Monitoring in Broadhaven Bay 2010 Pia Anderwald Mary Coleman Mairead O Donovan Roisin Pinfield Laura Walshe Damien Haberlin Mark Jessopp Michelle Cronin Coastal and Marine Research Centre Environmental Research Institute University College Cork Ireland Citation: Anderwald, P., Coleman, M., O Donovan, M., Pinfield, R., Walshe, L., Haberlin, D., Jessopp, M. and Cronin, M. (2011). Marine mammal monitoring in Broadhaven Bay Progress Report to RSK Environment Limited Group. Coastal and Marine Research Centre, University College Cork, Ireland. University College Cork, 2011 EPA Export :23:35:14

3 CONTENTS Summary 1 1. Introduction Background Broadhaven Bay SAC Marine Mammal Fauna Aims 5 2. Methods Study area Visual effort Line-transects Cliff watches fieldwork Analysis temporal occurrence Spatial distribution Acoustic effort Calibration Data processing Photo-ID Fieldwork Analysis Results Visual effort Seasonal occurrence Models of temporal occurrence Spatial distribution Acoustic effort Spatial and seasonal patterns of occurrence Calibrations Photo-ID Discussion 51 Acknowledgements 54 References 55 EPA Export :23:35:14

4 SUMMARY Following on from 2002, 2005 and , the marine mammal monitoring programme in Broadhaven Bay, NW Mayo, was continued in Effort consisted of 69 days (312 onehour scans) of cliff-based observations between February and November, 6 line-transects, 10 photo-id trips and year-round acoustic monitoring using 4 C-PODs. A total of 9 marine mammal species was recorded from cliff-based observations, comprising minke and killer whales, bottlenose, common, Risso s and white-beaked dolphins, harbour porpoise, grey and harbour seals. Of these, the grey seal accounted for the highest number of sightings (n=93), while the most frequently recorded cetacean species was the common dolphin with 32 sightings (ca individuals). 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 recorded between April and September, and Risso s dolphin between June and September. Minke whales have been observed in every month between March and November. Taking into account environmental variables such as sea surface temperature and tidal state, and correcting for effort and sightings efficiency, results from Generalised Additive Models (GAM s) showed significantly lower occurrence of the coastal species bottlenose dolphin, grey and harbour seals during June to September 2005, 2008 and 2009, by comparison to the baseline in However, the daily presence of both grey and harbour seals during 2010 was not different from baseline levels, while bottlenose dolphin occurrence in 2010 remained significantly lower than in Such a pattern was not evident for the two species which occur mainly in the outer part of Broadhaven Bay, i.e. common dolphin (with a peak in occurrence in 2010) and minke whale (with no significant interannual difference in occurrence). Acoustic monitoring using C-PODs showed spatial differences in the use of the study area by the small odontocetes, with detection rates of both harbour porpoises and dolphin spp. consistently higher off Gubastuckaun in the outer part of Broadhaven Bay than in the inner part in Rossport Bay during all months of the year. Detection rates for harbour porpoises peaked in winter (December 2009 & January 2010), while dolphin presence was highest during spring (April) and late summer (August & September). After the 2010 field season, the Broadhaven Bay bottlenose dolphin photo-id catalogue numbers a minimum of 181 individuals (115 recognisable from both sides, 66 left, and 57 right sides). Individual dolphins were photographed in up to 10 different encounters between September 2008 and October 2010, and one third of animals were seen in both 2009 and 2010, indicating a relatively high degree of site fidelity, especially when considering the small size of the study area. 1 EPA Export :23:35:14

5 1. INTRODUCTION 1.1. Background Noise from underwater industrial construction activity such as pile-driving, rock-trenching or dredging has the potential to mask acoustic communication by marine mammals, cause behavioural changes or 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 (with harbour porpoise, as an example, showing a low threshold for Temporary Threshold Shift (TTS); Lucke et al., 2007; Southall et al., 2007), 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). Mitigation measures during construction activities in areas of marine mammal occurrence therefore include ramp-up procedures and the use of dedicated observers onboard construction vessels with the authority to postpone or stop construction work if marine mammals are present in the immediate vicinity. Although not a mitigation measure per se, 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, etc.). 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. The project is managed independently by RSK Environment Ltd and undertaken by CMRC. It has since continued in each year of construction activity, i.e. during 2002, 2005, and continuously (including winter months) since 2008 (Ó Cadhla et al., 2003; Englund et 2 EPA Export :23:35:14

6 al., 2006; Coleman et al., 2009; Visser et al., 2010). 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 The construction activity inevitably resulted in associated increase in boat traffic within Broadhaven Bay (up to a peak of 43 vessels at one point during June 2009). These vessels included construction vessels, the 300m pipe-lay 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. Further acoustic surveys were carried out in 2010 during late May and June, and a section of the nearshore pipeline had a further armour layer covering of rock placed during July. Site investigation works within Sruwaddacon Bay (Figure 1) resulted in increased vessel activity between Ballyglass and the entrance to Sruwaddacon Bay during crew changes between May and October The laying of the umbilical, which will provide hydraulic power, chemicals and controls for the offshore wellheads, is currently planned for Mitigation measures have included a) the use of marine mammal observers onboard construction vessels, and b) a code of conduct for vessels and personnel operating within Broadhaven Bay SAC (within the code of conduct a number of measures to mitigate impacts are included, such as soft-start to certain activities (acoustic surveys etc.) (NPWS, 2007) Broadhaven Bay SAC 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 It was put forward for this designation due to: 3 EPA Export :23:35:14

7 (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; (ii) the presence of a number of unusual marine communities and species, and (iii) 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 1b), is designated as a Special Protection Area (SPA) and in addition to the nearby Glenamoy Bog complex SAC, is important for wintering wildfowl species (in particular the brent goose (Branta bernicla)) Marine Mammal Fauna 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 protected by a range of legislative instruments, which include the Wildlife Act (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 (Halichoerus grypus) and harbour seal (Phoca 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). In 4 EPA Export :23:35:14

8 addition, the area represents an important habitat for both grey and harbour (common) seals, as well as otters. Based on data collected up to the end of 2009, the four Annex II species accounted for 61% of all marine mammal sightings within the bay between June and September (n = 371 sightings). Bottlenose, Risso s (Grampus griseus), short-beaked common (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 (Balaenoptera acutorostrata), sei (Balaenoptera borealis) and 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 (Visser et al., 2009; personal observations). To summarise, the importance of Broadhaven Bay as a marine mammal habitat is thus reflected by: - its high species diversity; - the regular occurrence of all four 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., 2005; Cronin et al., 2007), and; - its use as a foraging ground by at least nine marine mammal species, including all four Annex II species Aims The monitoring programme aims to examine the potential impact of construction activities from the installation of the Corrib gas pipeline on marine mammals within the area of Broadhaven Bay SAC. It combines land-based observations from cliff-top vantage points, boat-based line-transect surveys, photo-id and passive acoustic monitoring. The objectives include: 5 EPA Export :23:35:14

9 1. To provide an assessment of cetacean 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 of 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. 6 EPA Export :23:35:14

10 2. METHODS 2.1. 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 ca. 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. The approximate delineation of Rossport Bay (easternmost inner area) within Broadhaven Bay can be seen in Figure 1 (shown by the red line). Pipeline route Vessel corridors a) 7 EPA Export :23:35:14

11 Rossport Bay b) Figure 1. Study area of Broadhaven Bay and surrounding area. a) pipe-line route (dotted line) and vessel routes (yellow corridors); b) sites for land-based watches (green stars), with Gubastuckaun and Doonanierin representing the primary sites, and Pollacappul used only for boat counts during days of adverse weather conditions. Red circles represent the listening stations (LS) for acoustic monitoring using POD s; LS5 = calibration mooring used during July. N.B The red line shown in Fig. 1 a. and b. shows the approximate delineation of Rossport Bay, within the inner part of Broadhaven Bay. Sruwaddacon Bay 2.2. Visual effort Both land- and vessel-based surveys for marine mammals followed the same field protocols, using the same observation sites for cliff-top watches as in 2009 (Visser et al., 2010) and previous years of the monitoring programme (Ó Cadhla et al., 2003; Englund et al., 2006; Coleman et al., 2009). 8

12 Line-transects As in 2008 and 2009, line-transects were carried out on board the 40ft sea-angling boat An Gearóidín, with an observer height of ca. 3m above sea level. Transects were conducted along the same 9 parallel lines through the bay that were used previously (Ó Cadhla et al., 2003; Visser et al., 2010; Figure 2), at a speed of ca. 10knots. To ensure optimal sighting conditions, surveys were only carried out in sea states Beaufort Force 3 between April and October, at a frequency of at least once a month (weather conditions and boat availability permitting). Two observers scanned a 90 angle from the bow to the port and starboard sides respectively, 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 were used primarily to provide 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. Transect lines through Broadhaven Bay. 9

13 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 Analysis 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 a danger that the same animals are 10

14 counted more than once because they may use the same location for a prolonged period of time or leave temporarily only to 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. However, 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 detections (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 >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 <30min, and the difference between the minimum break duration and the following scan resulted in a scan of >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 < Beaufort Force 4; swell height 2m; visibility 7km. The temporal presence of marine mammals in an area can be influenced 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 understand what 11

15 parameters were influencing the presence of different marine mammal species in Broadhaven Bay throughout the study period, their presence was modelled against the following explanatory variables: sea surface temperature (SST), SST gradient, tidal state, sea state, daily observer effort, and year. Only the months of June to September had received coverage in each year of the monitoring programme since 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). Daily composites of sea surface temperature (SST) data were downloaded at 0.25 resolution from (source: GHRSST L4 AVHRR OI) for each day of cliff-based surveys. In addition to the SST data point closest to Broadhaven Bay (at 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, a SST coefficient of variation, termed the SST gradient, was calculated from the remaining data as (SST Max SST Min ) / SST Max. A high variation in SST over relatively small distances can be an indication for 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 12

16 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 interannual 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 (which relates the linear model to the binary response variable). 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 Un-Biased Risk Estimator (UBRE) score (Wood, 2006). The UBRE 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. Non-significant parameters were retained in the model if they contributed to minimising the UBRE score, but only significant parameters were plotted. 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 13

17 o Factor: - Year (2002 (= reference level); 2005; 2008; 2009; 2010) Spatial distribution Theodolite angles to animals recorded in the field were used to derive Irish National Grid coordinates (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 9.3) using the relevant scanned and geo-referenced section of the Admirality chart 2703 Broad Haven Bay and Approaches as a background. New cliff-height measurements carried out during 2010 allowed for sightings positions to be re-calculated, and previous years sightings were plotted according to the most recent calculations Acoustic effort Passive acoustic monitoring is frequently used in the study of cetaceans, 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. PODs (POrpoise Detectors) are automated, stationary, passive acoustic monitoring systems that detect and log odontocete echolocation clicks. Both T-PODs (Timed POrpoise Detectors) and C-PODs (full frequency Cetacean Detectors, designed to log the echolocation clicks of all small odontocetes) were used in this study. Following methods employed by Englund et al. (2006), T-PODs in Broadhaven were set to 130kHz to log porpoise vocalisations on four channels. The remaining two channels were set to 50kHz to log clicks centred below 100 khz in order to identify dolphin species. All T- PODs were set using TPOD.exe v8.24, the most up to date version of T-POD software available for setting T-PODs, viewing downloaded files, and data analysis. 14

18 T-PODs are no longer in production, although technical support is still available from the manufacturer (Chelonia Ltd, UK). The C-POD has superseded the T-POD. As C-PODs were recently developed in 2008, the accompanying software has been updated since All C- POD data collected in 2009 were therefore re-analysed using the most up-to-date version of the software (CPOD.exe v1.054). Since construction plans for 2002 had involved rock and sediment excavation within the Inner Broadhaven Bay area, an 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 small cetaceans entering or leaving the area. These three listening stations were deployed at an average depth of 17m at high tide and were deployed 500m apart in a straight line along a north to south axis (Ó Cadhla et al., 2003). C-PODs were deployed for the first time in Rossport Bay in April Acoustic monitoring was carried out at all four listening stations (LS) with T-PODs (LS1-3) and one C-POD (LS4) from November 2009 throughout the winter months for the first time since the onset of marine mammal monitoring in Broadhaven Bay. The C-POD off Gubastuckaun (LS4; Figure 1) was introduced in July 2009, and was deployed at a depth of 37m until September In order to ensure comparability between months, all seasonal trends presented in this report are based on C-POD detections since April Calibration T-POD monitoring ceased temporarily in April 2010 for the T-POD units to be tested by the manufacturer in order to ensure that they were still working correctly. C-PODs took over acoustic monitoring in Rossport Bay during these calibration trials. Following testing, both T- and C-PODs were subjected to at-sea calibration trials by mooring the units together at the same listening station: 15

19 - T-PODs: moored together at LS5 (Figure 1) from (which resulted in harbour porpoise, but no dolphin detections), and at LS6 (off Gubastuckaun near LS4) from and C-PODs: moored together at LS 4 from T- vs. C-PODs: two pairs moored together at LS3 and LS4, respectively, from Data processing Data were downloaded from the PODs onto a PC. Raw data are stored in click files, which are then queried by the POD software to identify porpoise and dolphin echolocation trains. This processing allows data to be exported from the train files as Detection Positive Minutes (DPM) per hour, which were subsequently summed by day and averaged per month Photo-ID Fieldwork The fieldwork protocol followed accepted standards for the photo-identification of bottlenose dolphins (for example, CCW (2005)). A group of animals was approached on a parallel course, at approximately the dolphins swimming speed, to a distance of ca. 30m. Dorsal fin photos were then taken using a digital Canon EOS 40D camera with a mm 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). 16

20 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 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; 17

21 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, an ongoing 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. 18

22 3. RESULTS 3.1. Visual Effort A total of six line-transects (on the following dates: 22.4., 15.6., 12.7., 15.8., 6.9. and ) were carried out during Sightings included minke whale, bottlenose and common dolphins, harbour porpoise, grey seal, harbour seal, unidentified seals, an otter and a sunfish (Figure 4). Land-based watches from Gubastuckaun and Doonanierin Point were conducted on 69 days (312 scans in good viewing conditions) in total between February and November No fieldwork was carried out in January and December due to adverse weather conditions. Effort was highest during the months of May (n = 11 days; 62 scans) and June (n=12 days; 68 scans), but comparatively good coverage could also be achieved during early and late season, with 5 days of effort per month in February, October and November (Figure 5). As in 2009 (Visser et al., 2010), grey seal accounted for the highest number of sightings of any marine mammal species in the study area. However, while bottlenose dolphin had been the most common cetacean species observed in Broadhaven Bay in 2009 with respect to both number of sightings and individuals, common dolphin was the most frequently recorded cetacean in With group sizes of up to 300 animals, common dolphin also accounted for the highest number of individuals, representing a 5-fold increase when compared with 2009 (Table 1). The only (uncommon) species which had been observed in the study area in one or more of the previous years but were not recorded during 2010 were sei whale (Balaenoptera borealis), Atlantic white-sided dolphin (Lagenorhynchus acutus) and marine turtles. 19

23 a) cetaceans b) seals 20

24 c) other species Figure 4. Sightings of a) cetaceans, b) seals and c) other species during line-transect surveys in

25 Figure 5. Monthly effort for each year, expressed as a) number of days watched (n=250), and b) total number of scans (n=1148). 22

26 Table 1. Summaries of all sightings for 2010, including cliff-based effort-related, opportunistic and vesselbased sightings. Black-shaded fields indicate presence of the species for that month in 2010; grey-shaded fields indicate that the species was not observed in 2010, but was present in the study area of Broadhaven Bay during that month in a previous year of the monitoring programme. No watches were conducted in January, and effort in December was low and restricted to one year of the study (see Figure 5). No. sight s 2010 No. ind. s 2010 Cetaceans Minke whale Sei whale Killer whale Bottlenose dolphin Common dolphin Risso s dolphin White-beaked dolphin Atlantic whitesided dolphin Harbour porpoise Unidentified dolphin Unidentified whale Unidentified cetacean Seals Grey seal Harbour seal Group size Seasonal presence 2010 Min Max F M A M J J A S O N Unidentified seal Other species Otter Basking shark Sunfish Unidentified turtle

27 Seasonal occurrence Patterns of seasonal species occurrence were largely consistent with findings from previous years. The presence of bottlenose and common dolphin, as well as grey seal, was confirmed for each month in which observations have taken place in Broadhaven Bay since the start of the monitoring programme (Table 1), except for the month of December with little effort. The same applied to harbour porpoise, although a visual record is still missing for the month of March. No clear seasonal pattern was detectable for bottlenose dolphin occurrence in any year of the project, neither for the proportion of scans that the species was present, nor for the number of individuals per scan (Figure 6b). By contrast, common dolphin occurrence had peaked in October during both 2008 and 2009, with 2010 still showing the highest occurrence in autumn, but an additional peak in February, especially when group size was taken into consideration. The summer months yielded a lower proportion of positive scans for the species (Figure 6c). Some species more typically occurring in the study area during the summer months (e.g. basking shark and minke whale (Figure 6a)) were observed unusually early in 2010, with a basking shark feeding off Gubastuckaun as early as March and minke whale presence recorded in Broadhaven Bay in every month from March to November now since the start of the project (Figure 6a). Similarly, the grey seal was present in the highest proportion of scans in June, September and particularly November after occurring primarily during summer months in 2008 and 2009 (Figure 6d). On the other hand, the presence of Risso s dolphins remained confined to the summer months and early autumn (June to September), and harbour seals have only been recorded in the study area between April and September to date, with a peak in occurrence during June or July since 2005, but September in 2002 (Table 1, Figure 6e). 24

28 Figure 6a. Seasonal occurrence of minke whales in Broadhaven Bay, expressed as proportion of scans in which the species was present (left panel) and average number of individuals per scan (right panel), for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort. 25

29 Figure 6b. Seasonal occurrence of bottlenose dolphins in Broadhaven Bay, expressed as proportion of scans in which the species was present (left panel) and average number of individuals per scan (right panel), for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort. 26

30 Figure 6c. Seasonal occurrence of common dolphins in Broadhaven Bay, expressed as proportion of scans in which the species was present (left panel) and average number of individuals per scan (right panel), for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort. 27

31 Figure 6d. Seasonal occurrence of grey seals in Broadhaven Bay, expressed as proportion of scans in which the species was present (left panel) and average number of individuals per scan (right panel), for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort. 28

32 Figure 6e. Seasonal occurrence of harbour seals in Broadhaven Bay, expressed as proportion of scans in which the species was present (left panel) and average number of individuals per scan (right panel), for each year of the monitoring programme. Broken lines represent months with no cliff-based visual effort. 29

33 Models of temporal occurrence No temporal change over the period of June to September (the months which received coverage in all years of the monitoring project) was apparent in the daily presence of minke whales (Table 2a) or grey seals (Table 2d) in the study area, when corrected for all other parameters in the Generalised Additive Models (see section 2.2.3, p. 14). By contrast, the presence of both bottlenose dolphins (Table 2b, Figure 7b) and harbour seals (Table 2e, Figure 7e) was significantly higher in June than in August, while common dolphins showed a linear increase in their presence from June to September (Table 2c, Figure 7c). The correction parameters for detectability (sea state) and effort (average number of scans per day between Gubastuckaun and Doonanierin) both showed the expected effect in the model for minke whale, with presence for this species decreasing linearly with increasing sea state and increasing with higher numbers of scans per day (Table 2a, Figure 7a). The same relationship was detected for grey seal, although the decrease in detectability with increasing sea state was not linear (Table 2d, Figure 7d). However, neither parameter had a significant influence on the detectability of bottlenose or common dolphins (Tables 2b,c; Figures 7b,c), and only the mean number of scans per day affected sightings of harbour seals (Table 2e, Figure 7e). The average difference in water height between high and low water for each day (as a measure for spring vs. neap tides) was retained in most models for better fit, but was not a significant predictor of the presence of any species when corrected for the other parameters. The presence of harbour seals showed a significant positive linear relationship with local sea surface temperature (Table 2e, Figure 7e), while this parameter did not influence the presence of any of the other four species. Finally, the factor Year was not necessary in explaining the presence of minke whales in the study area when the model included the smooth terms (Table 2a), but significant interannual differences were found in the presence of all the other four species. Common dolphins showed higher presence in Broadhaven Bay during 2010 in comparison with 2002 (Table 2c, Figure 7c), while no difference was detected between previous years of the project (2005, 2008 and 2009) and By contrast, bottlenose dolphin, grey and harbour seals showed similar interannual patterns of occurrence, with the daily presence of all three species 30

34 between June and September significantly reduced in 2005, 2008 (with no sightings of harbour seals at all) and 2009 in comparison with 2002 (Tables 2b,d,e, Figures 7b,d,e). In 2010, bottlenose dolphins still showed a lower presence than in 2002, while the presence of grey and harbour seals was not significantly different from the reference level. The model for the daily occurrence of harbour seals performed best, with 45.5% of the deviance explained (Table 2e), while the model for bottlenose dolphins only explained 20.8% of the deviance (Table 2b), indicating that a higher percentage of the variation in the data was unaccounted for by the model. Table 2a. Summary for final model of minke whale presence / absence per day (n=155). df = degrees of freedom, p = significance of parameter. Parametric coefficients Estimate ± std. error p Intercept ± <0.001 Year 2005 (vs. 2002) (vs. 2002) (vs. 2002) (vs. 2002) - - Smooth terms df Χ 2 p s(julian.day) s(sea.state) s(mean.no.scans) s(lwhw.range.height) s(sst) s(sst.gradient) Deviance explained: 26.9% 31

35 Table 2b. Summary for final model of bottlenose dolphin presence / absence per day (n=155). df = degrees of freedom, p = significance of parameter. Parametric coefficients Estimate ± std. error p Intercept ± Year 2005 (vs. 2002) ± (vs. 2002) ± < (vs. 2002) ± (vs. 2002) ± Smooth terms df Χ 2 p s(julian.day) s(sea.state) s(mean.no.scans) s(lwhw.range.height) s(sst) s(sst.gradient) Deviance explained: 20.8% Table 2c. Summary for final model of common dolphin presence / absence per day (n=155). df = degrees of freedom, p = significance of parameter. Parametric coefficients Estimate ± std. error p Intercept ± <0.001 Year 2005 (vs. 2002) ± (vs. 2002) ± (vs. 2002) ± (vs. 2002) ± Smooth terms df Χ 2 p s(julian.day) s(sea.state) s(mean.no.scans) s(lwhw.range.height) s(sst) s(sst.gradient) Deviance explained: 28.1% 32

36 Table 2d. Summary for final model of grey seal presence / absence per day (n=155). df = degrees of freedom, p = significance of parameter. Parametric coefficients Estimate ± std. error p Intercept ± Year 2005 (vs. 2002) ± < (vs. 2002) ± < (vs. 2002) ± (vs. 2002) ± Smooth terms df Χ 2 p s(julian.day) s(sea.state) s(mean.no.scans) s(lwhw.range.height) s(sst) s(sst.gradient) Deviance explained: 31.1% Table 2e. Summary for final model of harbour seal presence / absence per day (n=155). df = degrees of freedom, p = significance of parameter. Parametric coefficients Estimate ± std. error p Intercept ± Year 2005 (vs. 2002) ± (vs. 2002) no harbour seal sightings in (vs. 2002) ± < (vs. 2002) ± Smooth terms df Χ 2 p s(julian.day) s(sea.state) s(mean.no.scans) s(lwhw.range.height) s(sst) s(sst.gradient) Deviance explained: 45.5% 33

37 Figure 7a. GAM smoothing curves for significant parameters in final model for minke whale occurrence. Broken lines represent 2-SE ranges around the main effects. The degrees of freedom for each smoothing curve are indicated on the y-axis. Vertical dashes on the x-axis represent the distribution of the explanatory variable. Figure 7b. Parametric coefficient (Year) and smooth term (Julian day) significant in final model for bottlenose dolphin. 34

38 Figure 7c. Parametric coefficient (Year) and smooth term (Julian day) significant in final model for common dolphin. Figure 7d. Parametric coefficient (Year) and smooth terms (sea state and mean number of scans per day) significant in final model for grey seal. 35

39 Figure 7e. Parametric coefficient (Year) and smooth terms (Julian day, mean number of scans per day and SST) significant in final model for harbour seal Spatial distribution 36

40 The spatial distribution of marine mammal sightings in 2010 followed the same general pattern as in previous years, with minke whale (Figure 8a) and common dolphin (Figure 8c) occurring mainly in the outer part of Broadhaven Bay (Doonanierin Point Gubastuckaun and outward), whereas bottlenose dolphin (Figure 8b) and particularly grey seal (Figure 8g) were also observed in the inner bay, including Rossport Bay, and close to the coast. However, harbour porpoise sightings (Figure 8d) in 2010 were confined mainly to the outer bay area, while the species had also been observed further into the bay in previous years. Despite a higher number of harbour seal sightings compared to 2005, 2008 and 2009 (Figure 7e), animals were concentrated mainly around Gubastuckaun in 2010, with only two sightings of positively identified harbour seals in Rossport Bay (Figure 8h). However, some of the unidentified seals (Figure 8i) could account for more sightings of this species in the inner part of the bay. Comparable to previous years, both Risso s and white-beaked dolphin sightings occurred in the vicinity of Erris Head, while four of the five killer whale sightings in 2010 occurred outside the boundary of the SAC (Figure 8e). As expected, sightings of unidentified cetaceans tended to increase with increasing distance from the land-based observation sites (Figure 8f). Basking shark sightings were concentrated mainly around Gubastuckaun in 2010, while the species had been recorded over a wider area within the bay in previous years. The only otter sighting in 2010 occurred in Rossport Bay, consistent with previous years (Figure 8j). No difference was detected in the spatial distribution between cliff- and boat-based sightings for any species except grey seal, which showed a number of boat-based sightings around the north-eastern boundary of the SAC and near Ballyglass (Figure 8g), respectively, i.e. areas which cannot be viewed from the cliffs or are too far away to detect and positively identify seals. 37

41 a) Minke whale. Red symbols = sightings from 2010; dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. b) Bottlenose dolphin. Red symbols = sightings from 2010; dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. 38

42 c) Common dolphin. Red symbols = sightings from 2010; dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. d) Harbour porpoise. Red symbols = sightings from 2010; dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. 39

43 e) Other cetacean species f) Unidentified cetaceans 40

44 g) Grey seal. Red symbols = sightings from 2010, dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. h) Harbour seal. Red symbols = sightings from 2010, dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. 41

45 i) Unidentified seals. Red symbols = sightings from 2010, dark grey symbols = sightings from previous years (2002, 2005, ). Circles = sightings from cliff; squares = sightings from boat. j) Other species Figure 8. Spatial distribution of marine mammal sightings. Only first sightings are included. Green stars represent the land-based observation sites (including Pollacappul in the south, from which only opportunistic watches were conducted). 42

46 3.2. Acoustic Effort A total of 16,645 hours of acoustic data were obtained from the C-PODs between January and October 2010, compared to 17,518 hours in All the Inner Bay C-PODs (LS1-3) generally performed well throughout deployment periods. However, there was some loss of data due to internal C-POD malfunction at LS4 off Gubastuckaun during July (Figure 9) Figure 9. Total monthly effort (hours) for all four listening stations for 2009 (left panel) and 2010 (right panel). LS1 = Rossport North, LS2 = Rossport Centre, LS3 = Rossport South, LS4 = Gubastuckaun (see Figure 1). 43