Description: Acoustic presence data on Antarctic blue whales (Balaenoptera musculus intermedia) were obtained from passive acoustic monitoring (PAM) data collected at 63°59.56' S and 00°02.65' W, mooring AWI229-09, recorder SV1000, between December 2010 and June 2011. The passive acoustic recorder was of type Sono.Vault (manufactured by develogic GmbH, Hamburg, Germany) and attached to oceanographic deep-sea mooring AWI229-09 of the Hybrid Antarctic Float Observation System (HAFOS). It was deployed from December 2010 to December 2012, moored at a depth of 969 m and recorded continuously at a sample rate of 5.333 Hz. After recovery, the passive acoustic data were prepared for further analysis following the Standard Operating Procedures (SOP) for PAM data collected by the Ocean Acoustics Group of AWI according to Thomisch et al. (2023a, regarding definitions and terminology) and Thomisch et al. (2023b, with regard to data preparation procedures). Daily acoustic presence of Antarctic blue whales was assessed based on automated detections of Z-call vocalizations by spectrogram cross-correlation using a pre-defined spectrogram template in a frequency band from 17.5 to 29 Hz. Received levels were obtained for each detected Z-call, as sound pressure level SPLrms [dB re: 1μPa] within the 25–29 Hz band of each detected Z-call event, for details on automated detection please refer to Thomisch et al. (2016). To avoid a spatial mismatch between the actual position of calling animals and the recorders, ABW detections were filtered to only keep detections that originated from within a ~10 km radius from the recorders. Assuming a source level of 189 dB re: 1μPa over 25–29 Hz and a spherical transmission loss TL[dB] = 20log₁₀(r), approximate distances between vocalizing Antarctic blue whales and the respective recording site locations were estimated for each detected Z-call. Daily acoustic presences were estimated as days with at least one detection event within a ~10 km radius of the respective recording sites; i.e., Z-calls with calculated received levels of ≥109 dB, considering a nominal TL of 80 dB. Data presented in this publication series were used together in presence-only species distribution models (SDMs) to predict the year-round habitat suitability of Antarctic blue whales in the Weddell Sea (El-Gabbas et al., under review). Data contain information on the detection time and the estimated received level SPLrms [dB re: 1μPa] for each Antarctic blue whale vocalization within a ~10 km radius of recorder SV1000, mooring site AWI229-09.

Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Endangered Species Research 30 (2016): 239-253, doi:10.3354/esr00739.

Description: Distribution and movement patterns of Antarctic blue whales Balaenoptera musculus intermedia at large temporal and spatial scales are still poorly understood. The objective of this study was to explore spatio-temporal distribution patterns of Antarctic blue whales in the Atlantic sector of the Southern Ocean, using passive acoustic monitoring data. Multi-year data were collected between 2008 and 2013 by 11 recorders deployed in the Weddell Sea and along the Greenwich meridian. Antarctic blue whale Z-calls were detected via spectrogram cross-correlation. A Blue Whale Index was developed to quantify the proportion of time during which acoustic energy from Antarctic blue whales dominated over background noise. Our results show that Antarctic blue whales were acoustically present year-round, with most call detections between January and April. During austral summer, the number of detected calls peaked synchronously throughout the study area in most years, and hence, no directed meridional movement pattern was detectable. During austral winter, vocalizations were recorded at latitudes as high as 69°S, with sea ice cover exceeding 90%, suggesting that some Antarctic blue whales overwinter in Antarctic waters. Polynyas likely serve as an important habitat for baleen whales during austral winter, providing food and reliable access to open water for breathing. Overall, our results support increasing evidence of a complex and non-obligatory migratory behavior of Antarctic blue whales, potentially involving temporally and spatially dynamic migration routes and destinations, as well as variable timing of migration to and from the feeding grounds.