Fin whale (Balaenoptera physalus) acoustic presence off Elephant Island (South Shetland Islands), Antarctica

Summertime visual observations suggest that the region around Elephant Island may serve as an important feeding area for fin whales. To explore its year-round relevance, passive acoustic recordings collected northwest of Elephant Island (61°0.88’S, 55°58.53’W) from January 2013 to February 2016 were analysed for seasonal and diel patterns of fin whale 20 Hz calls. Calls were detected year-round, although in some years calls were not present during all months. For all years, fin whale calls were consistently present from March to July for more than 90% of days per month. From August to January, percentage of days with calls varied between years, with presence exceeding 75% of days per month throughout 2014, whereas in 2015 calls were absent in October and November. In 2013, fin whale calling dropped in August and increased again towards October and November. Quantitative analyses of power spectral density for the 20-Hz and 89-Hz fin whale bands, showed that fin whale acoustic power in both frequency bands followed a Gaussian-like temporal pattern, increasing in late January, peaking during April-May and decreasing in late August for all years. A second shoulder peak in PSD seemed to occur during the second part of July showing strongest for the upper fin whale band, followed by a rapid decrease, after which SNR for both bands dropped to zero. Diel patterns in call activity were analysed for a 10-month subset of the data from 2013. Fluctuations in call rates did not follow a diel pattern nor correspond to local insolation. The observed peaks in fin whale call activity correspond to the periods during which fin whale super groups have been observed visually in this region. Our year-round acoustic analysis indicates that the Elephant Island region likely carries an important role for fin whales throughout the entire year

Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.Keywords: Antarctic minke whale, Southern Ocean, Bio-duck, Acoustic monitoring, Balaenoptera bonaerensi

Passive Acoustic Monitoring (PAM) in the Southern Ocean: three generations of autonomous recorders in a basin wide array

Passive acoustic monitoring (PAM) has emerged as a highly efficient technology to conduct long-term monitoring of marine mammals at species dependent, local to basin scales, providing valuable new insights into species distributions and migration patterns. To study Antarctic mammals, we deployed up to ten moored, autonomous acoustic recorders in the Atlantic sector of the Southern Ocean. Due to this region’s remoteness, challenging accessibility, and ensuing logistic constraints, especially during winter, recording devices were/are deployed for two years or longer, resulting in high demands on their power efficiency and storage capability. Two types of recorders, AURAL and MARU, which were deployed in March 2008 and December 2008, respectively, were recovered in December 2010. More recently, a set of eight, newly developed recorders (SONOVAULT), were deployed in December 2010, and are scheduled for recovery in December 2012. While in-situ recordings are hence available for AURAL and MARU, for SONOVAULTs extensive laboratory tests have been performed. Based on these recordings, this paper provides a user-based comparison of these three types of acoustic recorders, discussing their technical specifications and limitations (including recent enhancements) along with their actual performance and data quality. The paper concludes with a discussion of future needs for long-term monitoring applications along with each instrument’s potential to meet such requirements

A noisy spring: the impact of globally rising underwater sound levels on fish

The underwater environment is filled with biotic and abiotic sounds, many of which can be important for the survival and reproduction of fish. Over the last century, human activities in and near the water have increasingly added artificial sounds to this environment. Very loud sounds of relatively short exposure, such as those produced during pile driving, can harm nearby fish. However, more moderate underwater noises of longer duration, such as those produced by vessels, could potentially impact much larger areas, and involve much larger numbers of fish. Here we call attention to the urgent need to study the role of sound in the lives of fish and to develop a better understanding of the ecological impact of anthropogenic noise

Individual variation in pup vocalizations and absence of behavioral signs of maternal vocal recognition in Weddell seals (\u3ci\u3eLeptonychotes weddellii\u3c/i\u3e)

Individually stereotyped vocalizations often play an important role in relocation of offspring in gregarious breeders. In phocids, mothers often alternate between foraging at sea and attending their pup. Pup calls are individually distinctive in various phocid species. However, experimental evidence for maternal recognition is rare. In this study, we recorded Weddell seal (Leptonychotes weddellii) pup vocalizations at two whelping patches in Atka Bay, Antarctica, and explored individual vocal variation based on eight vocal parameters. Overall, 58% of calls were correctly classified according to individual. For males (n = 12) and females (n = 9), respectively, nine and seven individuals were correctly identified based on vocal parameters. To investigate whether mothers respond differently to calls of familiar vs. unfamiliar pups, we conducted playback experiments with 21 mothers. Maternal responses did not differ between playbacks of own, familiar, and unfamiliar pup calls. We suggest that Weddell seal pup calls may need to contain only a critical amount of individually distinct information because mothers and pups use a combination of sensory modalities for identification. However, it cannot be excluded that pup developmental factors and differing environmental factors between colonies affect pup acoustic behavior and the role of acoustic cues in the relocation process

Spatio-temporal patterns of Antarctic blue whale (Balaenoptera musculus intermedia) vocal behavior in the Weddell Sea

Although Antarctic blue whales (Balaenoptera musculus intermedia) are known to occur throughout the Southern Ocean, undertaking seasonal migrations between their breeding and feeding grounds, knowledge on spatio-temporal patterns in their distribution is limited. Here, passive acoustic recordings collected over three years from four locations at different latitudes along the Greenwich meridian south of 59°S, provided data on patterns in occurrence of stereotyped 3-unit vocalizations of Antarctic blue whales in the Weddell Sea. Highest vocalization rates occurred during austral summer at all recording locations, with calls detectable during 10 months in recordings from 59°S and 66°S, over 11 months in recordings from 69°S and year-round in recordings from coastal waters off the Antarctic continent at 70°S. Antarctic blue whale acoustic activity showed seasonal maxima that differed in timing between recorders, but were consistently present between years. Onset of increased acoustic presence occurred in November-December in the northernmost recorder at 59°S, in January in the recorders at 66°S and 69°S and in February in the southernmost recorder at 70°S. These results are consistent with a southbound migration of vocalizing Antarctic blue whales with at least some individuals migrating as far south as the Antarctic coastal waters during austral summer. A secondary increase in acoustic activity occurred during March and April in the recorders at 59°S and 66°S, respectively, supporting previous suggestions that migration of Antarctic blue whales is segregated in time. The absence of a corresponding secondary maximum at 69°S hints towards not all individuals migrating this far south, and that migratory destinations (or alternatively, vocal activity) may hence be spatially segregated. The year-round presence of Antarctic blue whale calls off the Antarctic continent suggests that Antarcticas’ coastal polynyas, i.e. patches of open water where animals can surface to breathe, may provide important habitats for animals to overwinter in high latitude waters

Capturing Variability Marine Soundscapes: Elephant Island, Antarctica – A Case Study

Here we present a comprehensive description of the acoustic environment approximately 31 km west-northwest of Minstrel Point, Elephant Island, Antarctica at 210 m water depth based on three years (Jan 2013 – Feb 2016) of subsampled (5 min per hour) passive acoustic recordings. Long-term spectrograms reveal a notable recurrence of acoustic environments between years. Fin and Antarctic blue whale calls dominate the low (< 100 Hz) part of the biophonic spectrum energetically from end of January to late July/early August. November through early January are dominated by leopard seal vocalizations at around 300 Hz. Concurrently, the geophonic spectrum exhibits strong fluctuations between days, both due to storm and tidal influences, causing flow and shackle noise from the instrumentation itself. Manual analysis of every second day of the subsampled data by visual and aural screening (employing short term spectrograms) was used to examine the data in greater detail for additional acoustic contributions and to assign the various acoustic signatures to their sources. Six cetacean and two pinniped species were identified based on their acoustic signatures and analysed for seasonal and diel patterns in occurrence. Anthrophonic signatures were attributed to air guns on 3 % of the analysed days. Vessel noise was noted between 10 and 12 % of days on annual averages, occurring mainly in austral summer and fall with sporadic events throughout the remainder of the year. This work illustrates the value of soundscape studies and provides a first step towards understanding the actual contribution of sound sources in their respective acoustic context and overall local noise budget