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  • 1
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    Temporal patterns in the acoustic presence of baleen whale species in a presumed breeding area off Namibia (2019)
    Inter-Research
    In:  EPIC3MARINE ECOLOGY PROGRESS SERIES, Inter-Research, 620, pp. 201-214
    Details
    Publication Date: 2019-07-09
    Description: The eastern Atlantic Ocean is considered to provide important breeding and wintering habitats for several migratory cetacean species. The spatio-temporal distributions and migratory behaviors of cetaceans off southern Africa are nevertheless still poorly understood. This study investigated the temporal patterns of acoustic occurrence of baleen whales in a presumed baleen whale breeding area off Namibia using passive acoustic recordings collected between November 2011 and May 2013. Our results show seasonal acoustic presence of humpback whales Megaptera novaeangliae, fin whales Balaenoptera physalus and Antarctic minke whales B. bonaerensis from November to January and from June to August. Their acoustic absence from February to May possibly indicates that most animals migrated to other areas (presumably in higher latitudes) in austral summer to feed. By contrast, Antarctic blue whales B. musculus intermedia were acoustically present throughout the recording period, indicating that part of the population remains at lower latitudes year-round. Our findings support the presumed ecological importance of the oceanic area off Namibia, providing (part of) a suitable cetacean wintering and, possibly, breeding range or migratory corridor. Furthermore, the occurrence of Antarctic blue and minke whales off Namibia, concurrent with their reported acoustic presence in high-latitude feeding areas, adds to growing evidence that baleen whale migration is not obligate but much more dynamic than has long been assumed.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Year-round passive acoustic data reveal spatiotemporal patterns in marine mammal community composition in the Weddell Sea, Antarctica (2020)
    Inter-Research
    In:  EPIC3Marine Ecology Progress Series, Inter-Research, 638, pp. 191-206
    Details
    Publication Date: 2020-04-17
    Description: ABSTRACT: To date, the majority of studies investigating marine mammal distribution and behavior take a single-species perspective, which is often driven by the logistic difficulties of collecting appropriate data at sea. Passive acoustic monitoring, provided recording tools exhibit sufficient bandwidth, has the potential to provide insights into community structure as devices operate autonomously simultaneously collecting data on baleen, pinniped and toothed whale acoustic presence. Data can provide information on local species diversity, residency times and co-occurrence. Here, we used multi-year passive acoustic data from 6 sites in the Weddell Sea, Southern Ocean, to explore how local marine mammal community compositions develop over time and in relation to sea-ice. Diversity peaked in austral late spring and early summer, shortly before seasonal sea-ice break-up. The effective number of species exhibited little variation over time, reflecting that species remain in Antarctic waters throughout austral winter. Community composition showed almost complete seasonal overturn, indicating that species replace each other throughout the year. For all 6 sites, community dissimilarity increased with increasing temporal distance, reflecting temporal trends in community composition beyond seasonality. Several species exhibited significant positive or negative co-occurrence patterns over time. These seasonal associations were consistent across all 5 oceanic sites, but partly inversed at the Western Antarctic Peninsula recording site. This study shows that the application of biodiversity metrics to passive acoustic monitoring data can foster insights into the timing of behaviors and community composition, which can boost the interpretation of responses in the light of ongoing environmental changes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
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    Spatio-temporal patterns in acoustic presence and distribution of Antarctic blue whales Balaenoptera musculus intermedia in the Weddell Sea (2016)
    Inter-Research
    Details
    Publication Date: 2022-05-25
    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.
    Keywords: Passive acoustic monitoring ; Antarctic blue whale ; Balaenoptera musculus intermedia ; Baleen whale migration ; Southern Ocean
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Acoustic presence and vocal repertoire of bowhead whales (Balaena mysticetus) in eastern and central Fram Strait (2022)
    Frontiers Media SA
    In:  EPIC3Frontiers in Remote Sensing, Frontiers Media SA, 3, pp. 907105-, ISSN: 2673-6187
    Details
    Publication Date: 2022-11-08
    Description: 〈jats:p〉Bowhead whales (〈jats:italic〉Balaena mysticetus〈/jats:italic〉) of the East Greenland-Svalbard-Barents Sea (Spitsbergen) population are still considered endangered, but knowledge on spatio-temporal distribution patterns and behavioral aspects remains scarce, yet crucial for this population’s conservation. Long-term passive acoustic recordings were collected at five locations in central and eastern Fram Strait (78-79°N, 0-7°E) as part of the Ocean Observing System FRAM (Frontiers in Arctic Marine Monitoring). Data recorded in 2012 and 2016/2017 were analyzed for the acoustic occurrence of bowhead whales at hourly resolution using a combination of automated and manual analyses. Bowhead whales were acoustically present from autumn throughout the winter months (October-February) and occasionally in spring (March-June), supporting hypotheses that Fram Strait is an important overwintering area. Acoustic presence peaked between mid-November and mid-December with bowhead whale calls recorded almost daily, often hourly for several consecutive days. The observed peak in acoustic presence coincided with the presumed mating period of bowhead whales, starting in late winter, indicating that Fram Strait may also serve as a mating area. Detailed analyses of recordings of a single year and location revealed eight distinct bowhead whale song types, comprising simple songs and call sequences. No bowhead whales were recorded in summer (July-September), indicating that they had migrated to summering areas or resided outside the detection range. Compared to previous studies in western Fram Strait, bowhead whale detections in our recordings were less frequent and recorded songs were less complex. The observed regional differences in bowhead whale acoustic behavior across Fram Strait suggest that eastern Fram Strait may represent a less favorable part of the bowhead whale overwintering area.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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