RISK ASSESSMENT FOR MARINE MAMMAL AND SEABIRD POPULATIONS IN SOUTH- WESTERN IRISH WATERS (R.A.M.S.S.I.) Daphne Roycroft, Michelle Cronin, Mick Mackey, Simon N. Ingram Oliver O’Cadhla Coastal and Marine Resources Centre, University College Cork March 2007 HEA Higher Education Authority An tÚdarás um Ard-Oideachas CONTENTS i) Summary ii) Acknowledgements General Introduction Seabirds and marine mammals in southwest Ireland 2 Rationale for RAMSSI 6 Study sites 7 Inshore risks to seabirds and marine mammals 11 i. Surface pollution 11 ii. Ballast water 13 iii. Organochlorine pollution and antifoulants 14 iv. Disease 15 v. Acoustic pollution 15 vi. Disturbance from vessels 16 vii. Wind farming 17 viii. Mariculture 17 ix. Fisheries 19 Aims and Objective 22 References 23 Appendix 33 Chapter 1. Seabird distribution and habitat-use in Bantry Bay 1.1 Abstract 35 1.2 Introduction 35 1.3 Study site 37 1.4 Methods 37 1.4.1 Line transect techniques 37 1.4.2 Data preparation 40 1.4.3 Data analysis 45 1.5 Results 46 1.5.1 Modelling 46 1.5.2 Relative abundance 54 1.6 Discussion 59 1.7 References 66 1.8 Appendix 70 Chapter 2. Shore-based observations of seabirds in southwest Ireland 2.1 Abstract 72 2.2 Introduction 73 2.3 Methods 74 2.3.1 Shore-watch techniques 74 2.3.2 Analysis of relative abundance 75 2.3.3 Density calculation 77 2.3.4 Comparison of shore and boat-based densities 79 2.4 Results 80 2.4.1 Relative abundance 80 2.4.2 Density 87 2.5 Discussion 89 2.6 References 93 Chapter 3. Temporal variation in the use of haul-out sites by Harbour seals in Bantry Bay and the Kenmare River 3.1 Abstract 96 3.2 Introduction 97 3.3 Materials and Methods 99 3.3.1 Study site 99 3.3.2 Seal counts 102 3.3.3 Statistical modelling 102 3.4 Results 105 3.4.1 Seal counts 105 3.4.2 Model output and validation 106 3.5 Discussion 121 3.6 References 127 Chapter 4 Haul-out behaviour of Harbour Seals in the Kenmare River, Co. Kerry 4.1 Abstract 133 4.2 Introduction 134 4.3 Methods 136 4.3.1 Study site 136 4.3.2 Capturing and handling procedure and tag deployment 136 4.3.3 Tag operation 137 4.3.4 Information relay and interpretation 138 4.3.5 Statistical modelling 138 4.3.6 Bootstrap variance estimation 140 4.4 Results 141 4.4.1 Capture and tag deployment 141 4.4.2 Duration of transmission 141 4.4.3 Examination of haul-out data 142 4.4.4 Model outputs and validation 143 4.5 Discussion 163 4.5.1 Effects of time of day and tidal cycle on haul-out behaviour 163 4.5.2 Seasonal changes in haul-out behaviour 164 4.6 References 171 Chapter 5. Cetacean distribution and relative abundance in southwest Ireland 5.1 Introduction and methodology 180 5.2 Species accounts 180 5.2.1 Harbour porpoise 181 5.2.2 Common dolphin 182 5.2.3 Risso’s dolphin 183 5.2.4 Bottlenose dolphin 184 5.2.5 Minke whales 184 5.2.6 Fin whale 185 5.3 Conservation recommendations 189 5.4 References 190 Conclusions 192 Recommendations for future work 194 References 197 SUMMARY The rugged coastline of southwest Ireland is home to the highest concentrations of breeding seabirds in the country, as well as high numbers of resident and migrating cetacean species, many of which are of conservation concern. Furthermore, the sheltered inlets of Bantry Bay and the Kenmare River provide a base for important populations of Harbour seals, an Annex II species under the EU Habitat’s Directive. This inshore environment contains a variety of potential risks to seabirds and marine mammals, most notably from surface & acoustic pollution, fisheries and the rapidly expanding mariculture industry. The year-round distribution and habitat-use of seabirds and marine mammals in Ireland’s inshore marine environment is poorly studied. Such baseline data is critical for the assessment of the effects of anthropogenic disturbance on marine mammals and seabirds in the coastal environment. The main aim of this study was to establish the spatio-temporal distribution and habitat-use of seabirds and marine mammals in southwest Ireland. A total of 21 seabird species were recorded in the survey area during the course of the three-year study. Seabird communities around selected headlands in southwest Ireland were dominated by Manx shearwaters (Puffinus puffinus) and Northern gannets (Morus basanus) while the seabird community in Bantry Bay was dominated by auks (mainly guillemots and razorbills, Uria aalge and Alca torda). Diversity was high in Bantry Bay however the relative abundance of many seabird species was higher at the outer headlands. Peak numbers of many species occurred in autumn (August - October) and the tidal cycle did not significantly influence the abundance of any of the species studied. Vulnerable concentrations of seabirds in areas of high risk from oil-pollution were identified. Investigations of seabird habitat-use using generalized linear and generalized additive modelling in Bantry Bay revealed that seaward distance (the distance from the most inshore point of the study site) was a significant positive determinant of total seabird distribution in Bantry Bay. The density of many 1 seabird species was also positively related to distance from the nearest coast, while depth was a limiting factor in Phalacrocoracidae distribution. The possible conservation applications of this data for seabirds in similar habitats are discussed. The year round changes in harbour seal abundance and haul-out site use in southwest Ireland were investigated by carrying out year round counts of seals at haul-out sites over a two and a half year period. There was a difference in the seasonal patterns of seal abundance between haul-out sites. The effect of the time of day on seal abundance at haul-out sites varied between the sites and was only significant at sites that also showed a seasonal pattern in abundance. Fewer seals were observed during strong winds and rain. The haul-out behaviour and habitat use of individual seals was examined using telemetry. The haul-out behaviour of tagged seals varied over the tagging period with animals spending a higher proportion of time ashore post moult in October, decreasing over the winter months to a minimum in February. A strong tidal influence on haul-out behaviour was evident with tagged seals hauling-out more frequently at low tide. There was overall large variation in the patterns in behaviour over the tagging period (i) between individuals and (ii) between tidal periods for each individual. A minimum of six cetacean species were recorded over the course of the three year study, with the most abundant and widespread species being the Harbour porpoise (Phocoena phocoena) and Common dolphin (Delphinus delphis). Minke whales (Balaenoptera acutorostrata) were also common across the study site and at least one Fin whale (Balaenoptera physalus) was sighted from the outer headlands. Peak numbers of many species occurred in Autumn and calves or immature adults were present throughout the year. The findings of the study are discussed in relation to those conducted in different parts of the species geographical range and the significance of the information put into context of conservation management and monitoring requirements for the species. 2 ACKNOWLEDGEMENTS This research was made possible through funding from the Higher Education Authority (HEA, Prtl-3) and was facilitated by Coastal and Marine Resources Centre and the Department of Zoology, Ecology and Plant Science, University College Cork. This project was greatly enhanced by the expert supervision of Dr Tom Kelly and Dr Emer Rogan, of the Department of Zoology, Ecology and Plant Science, UCC. Thanks to: Dr Derek Scott for his Dursey Island cable-car taxi service; Ann & Brendan Finch for accommodation on Dursey Island; Ann & Jerome Harrington for allowing access to Black Ball Head; Mr Stephan O'Sullivan (Irish Lights) for allowing free access to Mizen Head signal-tower; Vicki O’Donnell for help with GIS mapping; Lesley Lewis, Pete Jones, Mark Wilson, Alain Zuur and Lisa Borges for advice on statistical analysis; Claire Pollock for help with correction factors; Tom Hubbard for assistance on a number of boat surveys; Steve Newton and the Birdwatch Ireland/Seabird 2000 crew for kindly providing breakdowns of breeding seabird counts for southwest Ireland; Dave Millard and colleagues at BIM, as well as Gavin Burnell, Julie Maguire and Claire Lehane for information on mussel suspension culture. Thanks to Bernie McConnell, Alisa Hall (SMRU), Declan O’Donnell, Clare Heardman (NPWS) and Allen Whittaker for help with seal tagging. All photographs in this report are the copyright of Mick Mackey and Michelle Cronin. 3 GENERAL INTRODUCTION 1 SEABIRDS & MARINE MAMMALS IN SOUTHWEST IRELAND The coastal and offshore waters of southwest Ireland are essential feeding grounds for many seabirds and marine mammals, including non-breeders and passage migrants, throughout the year. A total of 52 species of seabirds and 21 cetacean species have been recorded both on and off the Irish shelf (Berrow & Rogan, 1997; Pollock et al., 1997; Mackey et al., 2004a; Mackey et al., 2004b). The heavily indented, cliff-edged coastline of Ireland with its numerous offshore islands and accessible rich feeding grounds, offers an ideal base for the formation of seabird colonies. A total of 24 seabird species breed in the Republic of Ireland (Mitchell et al., 2004). Six of these are listed in Annex 1 of the E.U. Birds Directive (79/409/EEC) as species of conservation priority.