[MARMAM] new paper: a new index to quantify the foraging effort of marine predators

karine heerah karine.heerah at hotmail.fr
Mon Nov 2 08:41:14 PST 2015

Dear all,
We are pleased to share with you our publication entitled: "from high-resolution to low-resolution dive datasets: a new index to quantify the foraging effort of marine predators." K. Heerah, M. Hindell, C. Guinet and J-B Charrassin, Animal Biotelemetry 2015 (http://www.animalbiotelemetry.com/content/3/1/42)
This methodological paper presents a different approach to identifiy and calculate foraging effort in low-resolution dive profiles that are transmitted by satellite. We therefore believe this could be useful to the community as the method can be applied to different species. Please do not hesitate to contact us if you have any questions regarding the application of the method to your own dataset.
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 data sets (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: (i) calculate an accurate index of foraging effort based on the detection of vertical sinuosity switches (i.e. huntinghighres time), (ii) produce a SRDL equivalent low-resolution dataset using a broken stick algorithm; and (iii) 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.
All the best,

Karine Heerah------------------
PhD in Marine ecologyUPMC - IMAS
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