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Villiers en Bois, France

O'Toole M.,University of Tasmania | Hindell M.A.,University of Tasmania | Charrassin J.-B.,French Natural History Museum | Guinet C.,Center Biologique Of Chize
Marine Ecology Progress Series

A total of 79 (37 juvenile male, 42 adult female) southern elephant seals Mirounga leonina from the Kerguelen Islands were tracked between 2004 and 2009. Area-restricted search patterns and dive behaviour were established from location data gathered by CTD satelliterelayed data loggers. At-sea movements of the seals demonstrated that >40% of the juvenile elephant seal population tagged use the Kerguelen Plateau during the austral winter. Search activity increased where temperature at 200 m depth was lower, when closer to the shelf break, and, to a lesser extent, where sea-surface height anomalies were higher. However, while this model explained the observed data (F1,242 = 88.23, p < 0.0001), bootstrap analysis revealed poor predictive capacity (r2 = 0.264). There appears to be potential overlap between the seals and commercial fishing operations in the region. This study may therefore support ecosystem-based fisheries management of the region, with the aim of maintaining ecological integrity of the shelf. © Inter-Research 2014. Source

Jaud T.,Center Biologique Of Chize | Dragon A.-C.,Center Biologique Of Chize | Garcia J.V.,Center Biologique Of Chize | Guinet C.,Center Biologique Of Chize

Recently, a number of Antarctic marine environmental studies have used oceanographic parameters collected from instrumented top predators for ecological and physical information. Phytoplankton concentration is generally quantified through active measurement of chlorophyll fluorescence. In this study, light absorption coefficient (K0.75) was used as an indicator of phytoplankton concentration. This measurement, easy to obtain and requiring low electric power, allows for assessing of the fine scale horizontal structuring of phytoplankton. As part of this study, Southern elephant seals (SES) were simultaneously equipped with a fluorometer and a light logger. Along the SES tracks, variations in K0.75 were strongly correlated with chlorophyll, a concentration measured by the fluorometer within the euphotic layer. With regards to SES foraging behaviour, bottom depth of the seal's dive was highly dependent on light intensity at 150 m, indicating that the vertical distribution of SES's prey such as myctophids is tightly related to light level. Therefore, change in phytoplankton concentration may not only have a direct effect on SES's prey abundance but may also determine their vertical accessibility with likely consequences on SES foraging efficiency. © 2012 Jaud et al. Source

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