Seasonal and interannual dynamics of Weddell seal ecology in East Antarctica: influences of sea ice and topography

In this study, we tried to:
i) provide a detailed description of the foraging ecology of the Dumont d'Urville Weddell seal population, describing their distribution throughout the year and the seasonal and circadian dive cycles in relation to key physical parameters of their habitat;
ii) examine the potential interannual variability in their diving and foraging behaviour and its relationship with landfast ice dynamics;
iii) investigate the link with fish distribution in the area, for known Weddell seals’ prey.

Three types of data are available in this dataset:
i) Conductivity Temperature Depth Satellite Relayed Data Loggers (CTD-SRDLs) were deployed on Weddell seals in Terre Adélie (East Antarctica) at Dumont d'Urville Station (−66.66◦, 140.00◦) between 2066 and 2024, to study animals’ movements and dives. The tags transmit information on their behaviour and location using the Argos satellite system. The data presented here includes the raw data transmitted by the tag, and the filtered data for analysis.
ii) In February 2006 and 2007, 33 high-definition video surveys were performed at the Pierre Lejay Bay, around the Dumont d’Urville station using a remotely operated vehicle (ROV). The data presented here include all fish data observed on the ROV footage (number of individuals per hour per ROV station), and summarised data for Weddell seals prey species.
iii) Antarctic landfast ice data were obtained from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) satellite visible and thermal infrared imagery with a spatial resolution of 1 km and a fifteen-day time stamp. Prior to March 2018, landfast ice data were taken from the dataset of Fraser et al. (2020, Earth Syst. Sci. Data, doi: 10.5194/essd-12-2987-2020). After March 2018, landfast ice maps were produced ad hoc for the Dumont d'Urville region using individual cloud-free MODIS visible and thermal infrared imagery.

Weddell seals exhibited benthic, epibenthic, and pelagic dive patterns. Dive behaviour varied among years with no consistent inter-annual trends. Typical seasonal cycle in foraging behaviour was observed, with deeper dives and shorter hunting times in the autumn than during the winter. The foraging range this population is more restricted than that of other populations. They foraged within 50 km of Dumont d’Urville station (75% of locations). Most used areas featured shallow depths (<190 m) and steeper slopes (>3°), likely associated with canyon edges. As landfast ice formed in April, dive locations were concentrated near Dumont d’Urville. Fish were more abundant near canyons, dominated by Nothotenioidei (99.9%), mainly Trematomus newnesi, with Pleuragramma antarcticum larvae along canyon edges. Seal dive patterns aligned with fish distributions, with spatial and vertical overlap.

Further details on the data are presented in the ReadMe file.