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dc.contributor.authorWilliamson, Laura D.
dc.contributor.authorBrookes, Kate L.
dc.contributor.authorScott, Beth E.
dc.contributor.authorGraham, Isla M.
dc.contributor.authorBradbury, Gareth
dc.contributor.authorHammond, Philip S.
dc.contributor.authorThompson, Paul M.
dc.identifier.citationWilliamson , L D , Brookes , K L , Scott , B E , Graham , I M , Bradbury , G , Hammond , P S & Thompson , P M 2016 , ' Echolocation detections and digital video surveys provide reliable estimates of the relative density of harbour porpoises ' , Methods in Ecology and Evolution , vol. 7 , no. 7 , pp. 762-769 .
dc.identifier.otherPURE: 241385515
dc.identifier.otherPURE UUID: efd07297-b5f7-43e3-9d4a-7660c336ea71
dc.identifier.otherBibtex: urn:cd75a5ef76515b1ffb4ef9241bc5a5c0
dc.identifier.otherScopus: 84978861876
dc.identifier.otherORCID: /0000-0002-2381-8302/work/47531623
dc.identifier.otherWOS: 000379957400001
dc.descriptionThe collection of visual and acoustic data was funded by the UK Department of Energy & Climate Change, the Scottish Government, Collaborative Offshore Wind Research into the Environment (COWRIE) and Oil & Gas UK. Digital aerial surveys were funded by Moray Offshore Renewables Ltd and additional funding for analysis of the combined data sets was provided by Marine Scotland. Collaboration between the University of Aberdeen and Marine Scotland was supported by MarCRF.en
dc.description.abstract1. Robust estimates of the density or abundance of cetaceans are required to support a wide range of ecological studies and inform management decisions. Considerable effort has been put into the development of line-transect sampling techniques to obtain estimates of absolute density from aerial- and boat-based visual surveys. Surveys of cetaceans using acoustic loggers or digital cameras provide alternative methods to estimate relative density that have the potential to reduce cost and provide a verifiable record of all detections. However, the ability of these methods to provide reliable estimates of relative density has yet to be established. 2. These methodologies were compared by conducting aerial visual line-transect surveys (n = 10 days) and digital video strip-transect surveys (n = 4 days) in the Moray Firth, Scotland. Simultaneous acoustic data were collected from moored echolocation detectors (C-PODs) at 58 locations across the study site. Density surface modelling (DSM) of visual survey data was used to estimate spatial variation in relative harbour porpoise density on a 4 × 4 km grid. DSM was also performed on the digital survey data, and the resulting model output compared to that from visual survey data. Estimates of relative density from visual surveys around acoustic monitoring sites were compared with several metrics previously used to characterise variation in acoustic detections of echolocation clicks. 3. There was a strong correlation between estimates of relative density from visual surveys and digital video surveys (Spearman's ρ = 0·85). A correction to account for animals missed on the transect line [previously calculated for visual aerial surveys of harbour porpoise in the North Sea was used to convert relative density from the visual surveys to absolute density. This allowed calculation of the first estimate of a proxy for detection probability in digital video surveys, suggesting that 61% (CV = 0·53) of harbour porpoises were detected. There was also a strong correlation between acoustic detections and density with Spearman's ρ = 0·73 for detection positive hours. 4. These results provide confidence in the emerging use of digital video and acoustic surveys for studying the density of small cetaceans and their responses to environmental and anthropogenic change.
dc.relation.ispartofMethods in Ecology and Evolutionen
dc.rights© 2016 The Authors. Methods in Ecology and Evolution published by John Wiley & Sons Ltd on behalf of British Ecological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.en
dc.subjectDensity surface modellingen
dc.subjectDigital surveyen
dc.subjectDistance samplingen
dc.subjectHarbour porpoiseen
dc.subjectQH301 Biologyen
dc.titleEcholocation detections and digital video surveys provide reliable estimates of the relative density of harbour porpoisesen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews. School of Biologyen
dc.contributor.institutionUniversity of St Andrews. Sea Mammal Research Uniten
dc.contributor.institutionUniversity of St Andrews. Marine Alliance for Science & Technology Scotlanden
dc.contributor.institutionUniversity of St Andrews. Scottish Oceans Instituteen
dc.contributor.institutionUniversity of St Andrews. Centre for Research into Ecological & Environmental Modellingen
dc.description.statusPeer revieweden

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