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From high-resolution to low-resolution dive datasets: a new index to quantify the foraging effort of marine predators

Citation

Heerah, K and Hindell, M and Guinet, C and Charrassin, J-B, From high-resolution to low-resolution dive datasets: a new index to quantify the foraging effort of marine predators, Animal Biotelemetry, 3, (42) pp. 1-12. ISSN 2050-3385 (2015) [Refereed Article]


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Copyright Statement

© 2015 Heerah et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4) http://creativecommons.org/licenses/by/4.0/

DOI: doi:10.1186/s40317-015-0074-3

Abstract

Background

In the last decade, thousands of satellite-relayed data loggers (SRDLs) have been deployed, providing large datasets on marine predator movement patterns at sea and their diving behaviour. However, the latter is in a highly summarised, low-resolution form, from which it is difficult to make the sorts of important behavioural inferences that are possible from higher-resolution datasets (such as detection of likely foraging events). The main objective of this study was to develop a simple, but accurate tool to detect and quantify within-dive foraging periods in low-resolution dives.

Method

Two southern elephant seals were fitted with a head-mounted time depth recorder (TDR) (recording depth at 1 Hz) and an accelerometer (recording 3 axes of acceleration at 16 Hz) from which prey capture attempts were estimated (PrCA), and a Weddell seal was also fitted with a TDR (1 Hz).The resulting high-resolution dive profiles were used to: (1) calculate an accurate index of foraging effort based on the detection of vertical sinuosity switches (i.e. huntinghighres time); (2) produce an SRDL-equivalent low-resolution dataset using a broken stick algorithm; and (3) from each low-resolution dive calculate a set of candidate foraging effort indices.

Results

Huntinglowres time, which is the total time spent in decreased vertical velocity segments of the dive, was the foraging effort index that best correlated with huntinghighres time. Huntinghighres mode of SES dives (highly sinuous parts of high-resolution dives) was associated with 77 % of total PrCA. In comparison, Huntinglowres segments of SES dives were associated with 68 % of PrCA as well as with four times more PrCA than transitlowres segments.

Conclusion

We found a low-resolution index which indicates foraging activity within a highly summarised dive profile and which identified most PrCA, despite degraded information transmitted by SLDRs. Used in combination with other measurements of the in situ environment, the huntinglowres index could be used in numerous integrated marine ecology studies, such as habitat use studies that are crucial to facilitate more effective conservation.

Item Details

Item Type:Refereed Article
Keywords:foraging behaviour, seals, telemetry, Antarctic
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Antarctic and Sub-Antarctic Environments
Author:Heerah, K (Ms Karine Heerah)
Author:Hindell, M (Professor Mark Hindell)
ID Code:106522
Year Published:2015
Funding Support:Australian Research Council (DP0345010)
Deposited By:IMAS Research and Education Centre
Deposited On:2016-02-12
Last Modified:2016-05-24
Downloads:48 View Download Statistics

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