Description: Spatio-temporal patterns in Antarctic minke whale (Balaenoptera bonaerensis) vocal behaviour in the Weddell Sea. Antarctic minke whales (Baleanoptera bonaerensis) occur in open as well as ice-covered waters throughout the Southern Ocean. Their low visual detectability and ice-associated habitat makes the species difficult to study using traditional visual methods. The recent identification of Antarctic minke whale vocalizations now allows the use of passive acoustic monitoring to investigate year-round spatio-temporal patterns in occurrence in ice-covered areas. Here we present preliminary results on Antarctic minke whale occurrence patterns based on a multi-year passive acoustic data set from 6 locations throughout the Atlantic sector of the Southern Ocean. Analyses were based on daily presence of the bio-duck call, which is characterized by its repetitive nature, consisting of regular down-sweeped pulses with most energy located in the 50-300 Hz band. Antarctic minke whales were present at all six Antarctic recording locations from June to December, with highest presence occurring between August and November (〉80% of days with bioduck calls present). At the southernmost recording locations, the bioduck call was present up to ten months of the year. Substantial inter-annual variation in the seasonal on- and offset period of vocal activity was observed at the different recording positions, possibly corresponding to variation in local ice conditions.

Description: Passive acoustic monitoring enables data collection on marine mammals over large temporal and spatial scales and in remote areas such as the Arctic Ocean. Passive acoustic data are collected at different recording sites in eastern and central Fram Strait since 2012, contributing to the Arctic Observatory FRAM (FRontiers in Arctic Marine Monitoring). Here, data recorded at 78°50 N, 0°E from July to November 2012 were analyzed for the daily acoustic presence of marine mammals. Bowhead whales (Balaena mysticetus) were acoustically present during 12 days in October and during 16 days in November, but acoustically absent from July to September. Downsweep song (three types) was present both in October and November, while upsweep song (one type) was only present in October. Besides bowhead whales, blue whales (Balaenoptera musculus), fin whales (B. physalus), narwhals (Monodon monoceros), sperm whales (Physeter macrocephalus) and harp seals (Pagophilus groenlandicus) were recorded. Acoustic species interactions regarding the overlap of species-specific sounds in time and frequency range were explored. In this context, temporal and spectral overlap of biophonic (blue and fin whale vocalizations) and anthrophonic (airgun) signals were detected in the low-frequency (〈100 Hz) spectrum. Our results emphasize the importance of Fram Strait as marine mammal habitat, possibly providing (summer) feeding opportunities for blue and fin whales and an overwintering ground for bowhead whales and narwhals. Understanding the spatio-temporal patterns in the distribution and acoustic behavior of marine mammals considerably benefits the development of effective conservation and management strategies for critical habitats in the Arctic Ocean.

Description: 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.

Description: 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.

Description: 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.

Description: Recent visual observations suggest that the region around Elephant Island serves as an important feeding area for fin whales. Passive acoustic recordings collected northwest of Elephant Island (61°0.88’S, 55°58.53’W) from January 2013 to February 2016 were analysed manually for seasonal and diel patterns of fin whale 20 Hz calls. Overall, 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 February 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 November (present 80% of days per month). 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. During peak calling period, maximum calls amounted approximately to 80 per 10-minute file. Fluctuations in call presence outside the peak calling period may be explained by variation in local ice conditions as drift may temporally force the animals away to areas with reduced ice concentrations. Furthermore, delays in the timing of migration between age groups, sexes and/or reproductive classes may also affect temporal patterns in the clustering of calls. The observed peaks in fin whale call activity correspond to the periods during which fin whale super groups have been repeatedly observed visually in this region. Our year-round acoustic analysis indicates that the Elephant Island region is likely to play an important role for fin whales throughout the remainder of the year.