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  • SSuummmmeerr DDiissttrriibbuuttiioonn aanndd RReellaattiivvee AAbbuunnddaannccee ooff

    CCeettaacceeaannss ooffff tthhee WWeesstt CCooaasstt ooff IIrreellaanndd

    ShOp Surveys Unit

    Irish Whale and Dolphin Group

    Merchant’s Quay, Kilrush, Co. Clare

    Common Dolphins (© Dave Wall 2004)

  • IWDG Heritage Council Report 2004 Page 1 26/11/2004

    Summer Distribution and Relative Abundance of Cetaceans off the West Coast of Ireland

    A Report for the Heritage Council

    By

    Dave Wall

    ShOp Surveys Unit

    Irish Whale and Dolphin Group

    Merchants Quay, Kilrush, Co. Clare.

    Email: dave.wall@iwdg.ie Web: www.iwdg.ie/shopsurveys/

    Survey Team

    Dave Wall (Project Director)

    Joanne O’Brien

    John Meade

    Brendan Allen

  • IWDG Heritage Council Report 2004 Page 2 26/11/2004

    Index

    Summary …………………………………………………………………………………...........................................

    1. Introduction ………………………………………………………………………………………………………………

    2. Methods

    2.1 Survey Methods …………………………………………………...…...................................................

    2.2 Data Recording ………………………...…………… …………………………………………………..

    2.3 Data Analysis …………………………………………..…………………………………………………..

    3. Results

    3.1 Survey Leg Reports …………………………….………………...…...................................................

    3.1.1 Leg 1 - Shannon Approaches…………….…………………………………………………

    3.1.2 Leg 2 - North Coast……………………………………. ……….………………...…………

    3.1.3 Leg 3 - Rockall Bank …………………...….………..……..……………………...…………

    3.1.4 Leg 4 – North Coast ……………………………….……....……………………...…………

    3.1.5 Leg 5 – Cork/Kerry Coast ……………...………….……....……………………...…………

    3.2 Cetacean Species Distribution & Relative Abundance …………………………..............................

    3.2.1 Survey Effort ……………………………….…………………………………………………

    3.2.2 Species Distribution & Relative Abundance ………………………………………………

    3.2.2.1 Common Dolphin (Delphinus delphis) ………………………………………

    3.2.2.2 Atlantic White-Sided Dolphin (Lagenorhynchus acutus) ……………….…

    3.2.2.3 Bottlenose Dolphin (Tursiops truncatus) ……………………………………

    3.2.2.4 Harbour Porpoise (Phocoena phocoena) ………..…………………………

    3.2.2.5 Risso’s Dolphin (Grampus griseus) …………………………………………

    3.2.2.6 Pilot Whale (Globicephala melanea) ……..…………………………………

    3.2.2.7 Minke Whale (Balaenoptera acutorostrata) ………...………………………

    3.2.2.8 Fin Whale (Balaenoptera physalus) …………………………………………

    3.2.2.9 Unidentified Dolphin Species …………………………………………………

    3.2.2.10 Unidentified Whale Species …………………………………………………

    3.2.2.11 Basking Shark (Cetorhinus maximus) ………..……………………………

    3.2.2.12 Other Species …………………………………………………………………

    4. Conclusions ……………………………………………………………………………………………………..

    5. Acknowledgements …………………………………………………………………………………………….

    6. References ……………………………………………………………………………………………………….

    Appendix I : List of cetacean species recorded in Irish waters .………………………………………………………..

    Appendix II : Daily Wind Speed and Directions Recorded During Each Leg of the Survey ………………………..

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  • IWDG Heritage Council Report 2004 Page 3 26/11/2004

    Summary

    From May to September 2004 the Irish Whale and Dolphin Group conducted a survey of

    cetacean (whale, dolphin and porpoise) distribution and relative abundance (abundance per

    unit effort) on board the State offshore research vessel, R.V. Celtic Explorer. The survey was

    operated as an ancillary project of the Geological Survey of Ireland’s National Seabed Survey

    and facilitated by the Irish Marine Institute.

    Eight species of cetacean were identified in the survey area: Common Dolphin (Delphinus

    delphis), Atlantic White-sided Dolphin (Lagenorhynchus acutus), Pilot Whale (Globicephala

    melas), Harbour Porpoise (Phocoena phocoena), Risso’s Dolphin (Grampus griseus),

    Bottlenose Dolphin (Tursiops truncatus), Minke Whale (Balaenoptera acutorostrata) and Fin

    Whale (Balaenoptera physalus).

    The most abundant cetacean species over the Irish shelf was the common dolphin reaching a

    maximum relative abundance of 17.5 animals per hour (aph) off the west Cork coast. In

    offshore waters over the Rockall Bank, the Atlantic White-sided dolphin was the most abundant

    species, reaching a maximum density of 14.5aph over the southern end of the bank (see

    relative abundance results).

    The relative abundance of cetacean species off the north Donegal and Derry coasts was

    extremely low, despite the highest survey effort being focused on these areas. Surveys

    conducted in the same areas during autumn and winter 2003/2004 also recorded low cetacean

    relative abundance in these areas and further survey effort is required in order to determine

    whether cetacean abundance off the north coast remains at such a low level all year round.

    This was the first major offshore cetacean survey conducted on the west coast by the IWDG as

    part of its Ships of Opportunity (ShOp) survey programme. The data from this survey has

    begun to highlight major differences in species occurrence and relative abundance between

    the north and south coasts and between offshore banks and the Irish shelf itself.

    The results of this survey have shown that surveys of distribution and relative abundance,

    conducted on board ships of opportunity, provide a cost effective and practical method of

    monitoring cetacean population in Ireland’s offshore habitats. Further effort is required to

    identify seasonal trends and to examine the effects of bathymetry, food availability and other

    oceanographic factors on cetacean distribution and abundance. Future survey effort should be

    promoted on board platforms of opportunity such as research vessels and naval vessels to

    achieve year-round monitoring of seasonal and multi-annual trends in cetacean distribution and

    relative abundance in Irish waters.

  • IWDG Heritage Council Report 2004 Page 4 26/11/2004

    1. Introduction

    The waters of Ireland’s Exclusive Economic Zone (EEZ) represent one of the most important

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

    have been recorded in Irish waters (see appendix I).

    All cetacean species in Irish waters are protected by the 1976 Wildlife Act 20 (and Wildlife

    Amendment Act 2000 21) and Irish waters, including the EEZ were declared a whale and

    dolphin sanctuary in 1991. All cetacean species are protected under the EU Habitats Directive 22 and the harbour porpoise and bottlenose dolphin are listed under Annexe II of the habitats

    directive, requiring the designation of Special Areas of Conservation (SACs) for their

    protection.

    As part of the 2004 Seabed Survey conducted by the Geological Survey of Ireland and the

    Marine Institute, the Irish Whale and Dolphin Group (IWDG) conducted an ancillary survey of

    cetacean distribution and relative abundance on board the R.V. Celtic Explorer.

    IWDG Ships of opportunity Surveys (ShOp Surveys)

    The IWDG has operated a cetacean strandings 1 and sightings 2 recording scheme in Ireland

    since 1991. Data from these schemes has highlighted the distribution and relative abundance

    of cetacean species in inshore waters but have provided limited knowledge of the occurrence

    of cetaceans in offshore habitats.

    In order to increase knowledge of cetacean distribution and abundance in offshore habitats,