Recommendations for photo-identification methods used in capture-recapture models with cetaceans
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Capture-recapture methods are frequently employed to estimate abundance of cetaceans using photographic techniques and a variety of statistical models. However, there are many unresolved issues regarding the selection and manipulation of images that can potentially impose bias on resulting estimates. To examine the potential impact of these issues we circulated a test data set of dorsal fin images from bottlenose dolphins to several independent research groups. Photo-identification methods were generally similar, but the selection, scoring, and matching of images varied greatly amongst groups. Based on these results we make the following recommendations. Researchers should: (1) determine the degree of marking, or level of distinctiveness, and use images of sufficient quality to recognize animals of that level of distinctiveness; (2) ensure that markings are sufficiently distinct to eliminate the potential for “twins” to occur; (3) stratify data sets by distinctiveness and generate a series of abundance estimates to investigate the influence of including animals of varying degrees of markings; and (4) strive to examine and incorporate variability among analysts into capture-recapture estimation. In this paper we summarize these potential sources of bias and provide recommendations for best practices for using natural markings in a capture-recapture framework.
Urian , K , Gorgone , A , Read , A J , Balmer , B , Wells , R S , Berggren , P , Durban , J W , Eguchi , T , Rayment , W & Hammond , P S 2015 , ' Recommendations for photo-identification methods used in capture-recapture models with cetaceans ' Marine Mammal Science , vol 31 , no. 1 , pp. 298–321 . DOI: 10.1111/mms.12141
Marine Mammal Science
© 2014 Society for Marine Mammalogy. This is the peer reviewed version of the following article: Urian, K., Gorgone, A., Read, A., Balmer, B., Wells, R. S., Berggren, P., Durban, J., Eguchi, T., Rayment, W. and Hammond, P. S. (2015), Recommendations for photo-identification methods used in capture-recapture models with cetaceans. Marine Mammal Science, 31: 298–321, which has been published in final form at https://dx.doi.org/10.1111/mms.12141. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
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