Using T-PODs to assess variations in the occurrence of coastal bottlenose dolphins and harbour porpoises

1.Assessments of anthropogenic impacts on cetaceans are often constrained by limited data on the extent to which these species use particular areas. 2.Timing porpoise detectors (T-PODs) are autonomous data recorders for detecting cetacean echolocation clicks, potentially providing cost-effective opportunities for monitoring cetacean occurrence. 3.The performance of T-PODs was assessed in three areas off the Scottish east coast, where the relative occurrence of bottlenose dolphins and harbour porpoises was known to differ. Land-based observations in one area compared visual and acoustic detections of dolphins, while direct hydrophone recordings of dolphin echolocation clicks were compared with T-POD detections during boat surveys. 4.Land-based surveys recorded 89 groups of dolphins within 900 m of the T-POD. All groups spending >30 min in the area were detected on the T-POD, and the probability of detection declined in relation to distance from the recording site. 5.The number of dolphin clicks recorded on the independent hydrophone system was significantly related to the number detected by a T-POD. Between pairs of T-PODs, there was also significant correlation with the numbers of clicks recorded in each hour, both for channels set to detect bottlenose dolphins and for channels set to detect harbour porpoises. 6.Year-round deployments of paired T-PODs detected significant geographical variation in detections for both bottlenose dolphins and harbour porpoises. This pattern reflected published data from visual surveys, where dolphins occurred most regularly within the Moray Firth Special Area of Conservation, and porpoises were sighted more regularly in offshore waters. 7.T-PODs do not detect all cetaceans in the area, and care must be taken when interpreting data from mixed species communities. Nevertheless, these results confirm that T-PODs provide an effective method for monitoring the occurrence of bottlenose dolphins and harbour porpoises, and provide excellent potential for collecting baseline data from poorly studied areas and monitoring long-term temporal change in key areas of interest. Copyright © 2009 John Wiley & Sons, Ltd.

[1]  S. Ingram,et al.  Using T-PODs to investigate the echolocation of coastal bottlenose dolphins , 2007, Journal of the Marine Biological Association of the United Kingdom.

[2]  Frank Thomsen,et al.  On the performance of automated porpoise-click-detectors in experiments with captive harbor porpoises (Phocoena phocoena). , 2005, The Journal of the Acoustical Society of America.

[3]  Roger Mundry,et al.  Geographical and seasonal variation of harbour porpoise (Phocoena phocoena) presence in the German Baltic Sea revealed by passive acoustic monitoring , 2007, Journal of the Marine Biological Association of the United Kingdom.

[4]  David L. Borchers,et al.  Abundance of harbour porpoise and other cetaceans in the North Sea and adjacent waters , 2002 .

[5]  Peter G. H. Evans,et al.  Monitoring cetaceans in European waters , 2004 .

[6]  Paul M. Thompson,et al.  Functional mechanisms underlying cetacean distribution patterns: hotspots for bottlenose dolphins are linked to foraging , 2004 .

[7]  P. Thompson,et al.  Fine-scale habitat selection by coastal bottlenose dolphins: application of a new land-based video-montage technique , 2003 .

[8]  J. Teilmann,et al.  Impacts of offshore wind farm construction on harbour porpoises: acoustic monitoring of echolocation activity using porpoise detectors (T-PODs) , 2006 .

[9]  W. Au,et al.  Transmission beam pattern and echolocation signals of a harbor porpoise (Phocoena phocoena). , 1999, The Journal of the Acoustical Society of America.

[10]  P. Hammond,et al.  Habitat preference modelling as a conservation tool: proposals for marine protected areas for cetaceans in southern Spanish waters , 2005 .

[11]  J. Barlow,et al.  Acoustic detections of singing humpback whales (Megaptera novaeangliae) in the eastern North Pacific during their northbound migration. , 1999, The Journal of the Acoustical Society of America.

[12]  P. Thompson,et al.  Distribution of small cetaceans within a candidate Special Area of Conservation; implications for management , 2003 .

[13]  Shannon Rankin,et al.  Acoustic detection and satellite-tracking leads to discovery of rare concentration of endangered North Pacific right whales , 2006, Biology Letters.

[14]  J. Gordon,et al.  Bioacoustics: A tool for the conservation of cetaceans in the Mediterranean Sea , 1997 .

[15]  B. Wilson,et al.  Violent interactions between bottlenose dolphins and harbour porpoises , 1996, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[16]  Marie A Roch,et al.  Classification of Risso's and Pacific white-sided dolphins using spectral properties of echolocation clicks. , 2008, The Journal of the Acoustical Society of America.

[17]  C. Weir,et al.  Cetaceans of the Atlantic Frontier, north and west of Scotland , 2001 .

[18]  Sven Koschinski,et al.  Reactions of harbor porpoises Phocoena phocoena and herring Clupea harengus to acoustic alarms , 2001 .

[19]  Whitlow W. L. Au,et al.  The Sonar of Dolphins , 1993, Springer New York.

[20]  Linda S. Weilgart.  The impacts of anthropogenic ocean noise on cetaceans and implications for management , 2007 .

[21]  Patrick N. Halpin,et al.  Techniques for cetacean-habitat modeling , 2006 .

[22]  Jay Barlow,et al.  ESTIMATES OF SPERM WHALE ABUNDANCE IN THE NORTHEASTERN TEMPERATE PACIFIC FROM A COMBINED ACOUSTIC AND VISUAL SURVEY , 2005 .

[23]  R. W. Floyd,et al.  Measurement of echolocation signals of the Atlantic bottlenose dolphin, Tursiops truncatus Montagu, in open waters. , 1974, The Journal of the Acoustical Society of America.

[24]  Paul M. Thompson,et al.  Using marine mammal habitat modelling to identify priority conservation zones within a marine protected area , 2009 .

[25]  B. Würsig,et al.  Protecting small cetaceans from coastal development: Impact assessment and mitigation experience in Hong Kong , 2009 .

[26]  J. Carlström.  Diel variation in echolocation behavior of wild harbor porpoises , 2005 .

[27]  P. Thompson,et al.  Habitat Use by Bottlenose Dolphins: Seasonal Distribution and Stratified Movement Patterns in the Moray Firth, Scotland , 1997 .

[28]  C W Clark,et al.  Calibration and comparison of the acoustic location methods used during the spring migration of the bowhead whale, Balaena mysticetus, off Pt. Barrow, Alaska, 1984-1993. , 2000, The Journal of the Acoustical Society of America.