ABSTRACTS OF POSTERS –ACOUSTICS


ac 30 the efficiency of static acoustic devices for monitoring bottlenose dolphins in a Special area of conservation


Sophie Hansen (1), Simon Berrow (1), David McGrath (1) (1) Galway-Mayo Institute of Technology hansen.sophie@web.de


Bottlenose dolphins are listed under Annex II of the EU Habitats Directive and thus member states must designate Special Areas of Conservation (SAC) and ensure that they are at a Favourable Conservation Status, which requires ongoing monitoring. The efficacy of static acoustic monitoring (SAM) techniques (using T-POD, C-POD and a hydrophone) for detecting bottlenose dolphins were compared to visual observations during 2008 and 2009 in the Lower River Shannon cSAC on the west coast of Ireland. A total of 252 hours with concurrent visual observations and acoustic monitoring were carried out. Overall, dolphins were observed during 8.9% of the total observation time while the T-POD (0.2%), C-POD (1.3%) and hydrophone (3.3%) performed less efficiently. When comparing simultaneous acoustic detections to visual observations, (the) SAM (equipment) successfully detected the presence of bottlenose dolphins even though the acoustic detection rate was 1.6% (T-POD), 15.3% (C-POD) and 29.2% (hydrophone) of the visual detection rate. Acoustic detection rates were all lower but generally consistent between years. There was a significant difference (p<0.04) between years by the T-POD with a higher proportion of DPM / h recorded in 2009 compared to 2008. There was no significant difference in visual detection rates (p>0.86) or that recorded by the hydrophone (p>0.53) between years. There were significantly less dolphin detections recorded by the C-POD compared with the hydrophone (p<0.025) in 2009 but more detections recorded by the C-POD than the T-POD (p<0.008). The percentage of dolphins observed but not recorded by the hydrophone was consistent between the two years (2008: 32%, 2009: 38%). Visual observations are restricted to favourable sea conditions during daylight hours which acoustic methods are not. Acoustic methods could provide a reliable method for monitoring dolphins and the consistency recorded here between years is encouraging.


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