Bottlenose dolphins in Connemara and Mayo 2008-2009. Movement patterns between two coastal areas in the west of Ireland. Report to the National Parks and Wildlife Service Department of the Environment, Heritage and Local Government November 2010 Machiel Oudejans 1, Simon Ingram 2,3 , Anneli Englund 3, Fleur Visser 1,4 & Emer Rogan 3 1. Dúlra Research, Belmullet, Co. Mayo. 2. School of Marine Sciences and Engineering, University of Plymouth, Plymouth, UK. 3. Department of Zoology Animal Ecology and Plant Sciences, University College Cork. 4. Kelp Marine Research, Amsterdam, The Netherlands. Index Abstract .................................................................................................................................3 1 Introduction .......................................................................................................................4 1.1 The bottlenose dolphin .................................................................................................4 1.2 Protection and conservation status ..............................................................................4 1.3 Bottlenose dolphins in Ireland .....................................................................................5 1.4 Project aims and objectives ..........................................................................................5 2 Methods ..............................................................................................................................6 2.1 Boat-based surveys .......................................................................................................6 2.2 Photograph analysis .....................................................................................................7 2.3 Severity of markings .....................................................................................................8 2.4 Matching catalogues ...................................................................................................8 2.5 Analysis of group structure ..........................................................................................9 3 Results ..............................................................................................................................10 3.1 Survey effort ...............................................................................................................10 3.2 Encounters with bottlenose dolphins .........................................................................11 3.3 Group size ..................................................................................................................12 3.4 Community characteristics .........................................................................................12 3.4.1 Mayo ....................................................................................................................12 3.4.2 Connemara ..........................................................................................................13 3.4.3 Mayo and Connemara catalogues combined .......................................................13 3.5 Population size ...........................................................................................................14 3.6 Resightings between Mayo and Connemara ..............................................................15 3.7 Site fidelity .................................................................................................................16 3.7.1. Mayo ...................................................................................................................16 3.7.2. Connemara .........................................................................................................17 3.7.3. Mayo and Connemara catalogues combined ......................................................17 3.8 Individual movement patterns ....................................................................................18 4 Discussion .........................................................................................................................20 5 Acknowledgements ..........................................................................................................24 6 References ........................................................................................................................25 7 Appendix I .......................................................................................................................28 2 Abstract A total of 46 dedicated and 33 opportunistic boat-based surveys were conducted in the coastal waters off Connemara and Mayo in 2008 and 2009, resulting in 31 encounters with groups of bottlenose dolphins. Between the two coastal areas, a total of 201 photo-identification records of dolphins were obtained, resulting in a minimum number of 177 individual dolphins identified. More dolphins were observed in northwest Mayo (n=179, 89% of the total number of identifications) than in Connemara (n=92, 46%). A total of 19 individuals (10.7%) were resighted in northwest Mayo between 2008 and 2009. The matching analysis of the Mayo photo-ID catalogue with the Connemara catalogue identified 70 individual dolphins that were sighted in both locations, representing 39.5% of the Mayo and 76.1% of the Connemara catalogues respectively. Twelve animals were recorded in both years in Mayo and in Connemara in 2009. The discovery curve for the combined catalogues showed a decline in the rate at which new dolphins were being added to the catalogue, suggesting that a substantial part of the total population occurring in these coastal areas in the summer of 2008-2009 has been identified. The large number of resightings, within groups and between both coastal sites, in combination with similar patterns of mark severity and age-class composition, strongly suggests that these dolphins all belong to the same social community. The mean sighting frequency per individual was higher in Mayo in 2009 (2.6 ± 1.4 SD) compared to frequencies recorded in Mayo in 2008 (1.2 ±1.2 SD) and Connemara (1.6 ± 1.0 SD). Individual movement patterns detected between both sites were identified as: (a) no movement (n=131); (b) single, one-way movements between the sites (n=24); (c), return journeys (n=36); or (d) a return journey followed by another one-way journey, described as the single-return move (n=7). Twenty-nine of the 31 encounters were recorded within 1-2 km off the coast, indicating that these inshore waters form an important habitat for these coastal communities. Two encounters with groups recorded in Mayo in September 2008 may belong to an offshore community. None of the dolphins encountered on these two occasions were resightings of known individuals from either coastal study area, and both groups consisted of dolphins of which a large proportion carried significant markings on the dorsal fin. 3 1 Introduction 1.1 The bottlenose dolphin The Common bottlenose dolphin ( Tursiops truncatus ) has a worldwide distribution across a wide range of habitats throughout temperate and tropical waters (Leatherwood & Reeves 1983). Its occurrence in coastal waters enables land-based monitoring and makes it one of the best studied cetacean species in the world. Despite their potential for long-distance movements, intraspecific differences in behaviour, site fidelity and ranging patterns have been described for geographically distinct populations (Würsig & Würsig 1977; Wells 1986; Bearzi et al. 1997; Wilson et al. 1999). Individual bottlenose dolphins can be recognised from their natural markings using photography (Würsig & Würsig 1977). Photo-identification of bottlenose dolphins relies on marks and nicks which the animal develops on its dorsal fins and flanks through social interaction with other dolphins and through interactions with human activities (Würsig & Würsig 1977). Photo-identification can be used to study social structure and population size, and to investigate movement patterns and habitat use by individual animals. Cetacean species that inhabit coastal areas are likely to be affected by human activities (Wells et al. 1994). Anthropogenic effects may be of particular concern for small coastal communities (Stockin et al. 2006), such as bottlenose dolphins along the west coast of Ireland. Recent concerns about effects of human activities on the Irish marine environment, especially the development of offshore hydrocarbon exploration, has induced the initiation of a series of research projects studying the distribution and abundance of cetaceans in Irish inshore, as well as offshore waters (Ó Cadhla et al. 2003, 2004; Wall et al. 2006; Roycroft et al. 2007; Visser et al. 2009). 1.2 Protection and conservation status All cetacean species occurring in Irish waters are protected under the 1976 Wildlife Act. In 1991, the Irish Economic Exclusion Zone (EEZ) was declared a whale and dolphin sanctuary by the Irish government. Under European law, the bottlenose dolphin is considered a priority species for conservation in European waters (Annex II of the European Union Habitats Directive [92/43/EEC]). The EU Habitats Directive requires countries to designate Special Areas of Conservation (SAC), based on i) population parameters ii) habitat vulnerability iii) 4 species’ range and iv) species’ conservation value. Given the protection status of bottlenose dolphins, it is important that any long- or short-term management decisions impacting on either the dolphins or their habitat are made with the support of detailed and current