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A novel method for analysing detection gaps in imperfect acoustic telemetry data to infer differential movements patterns in fish

Research output: Contribution to journalArticle

Michael J. Williamson, Emma Jayne Tebbs, Terence Peter Dawson, David J. Curnick, Francesco Ferretti, Aaron Carlisle, Taylor Chapple, Robert Schallert, David Tickler, Xavier A. Harrison, Barbara Block, David M. P. Jacoby

Original languageEnglish
JournalMethods in Ecology and Evolution
Publication statusSubmitted - 12 May 2020

King's Authors

Abstract

1 A wide array of technologies are available for gaining insight into the movement of wild aquatic animals. Although acoustic telemetry may lack the fine-scale resolution of some satellite tracking technologies, the substantially longer battery life can yield important long-term data on individual behaviour and movement for low per-unit cost. Typically, however, receiver arrays are designed to maximise spatial coverage at the cost of positional accuracy leading to potentially longer detection gaps as individuals move out of range between monitored locations. This is particularly true when these technologies are deployed to monitor species in hard-to-access locations.

2 We develop a novel approach to analysing acoustic telemetry data, using the timing and duration of gaps between animal detections to infer different behaviours. First, we define movement of animals between receivers and recursive loops from and to the same receiver. Then, using the durations of inter-, and intra-, receiver movements (i.e. detection gaps), we classify behaviours into ‘restricted’ or potential wider ‘out of range’ movements synonymous with longer distance dispersal. We apply this method to investigate spatial and temporal segregation of inferred movement patterns in two sympatric species of reef shark within a large, remote Marine Protected Area (MPA). Drivers of these movements were identified using network analysis, generalised linear mixed models and multi-model inference.

3 Species, diel period and season were significant predictors of ‘out of range’ movements. Silvertip sharks were overall more likely to undertake ‘out of range’ movements, compared to grey reef sharks, indicating spatial segregation, and corroborating previous stable isotope work between these two species. High individual variability in ‘out of range’ movements in both species was also identified.

4 We present a novel gap analysis of telemetry data to help infer differential movement and space use patterns where acoustic coverage is imperfect and other tracking methods mpractical at scale. In remote locations, inference may be the best available tool and this approach shows that acoustic telemetry gap analysis can be used for comparative studies in fish ecology, or combined, with other research techniques to better understand functional mechanisms driving behaviour.

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