Patterns in the Acoustic Presence and Vocal Behaviour of Bowhead Whales Balaena mysticetus in Eastern Fram Strait

Fram Strait, located between Greenland and Svalbard, provides a critical habitat to seasonally migrant and endemic cetaceans, including bowhead whales Balaena mysticetus of the Spitsbergen population. This population has been depleted close to the point of extinction by commercial whaling and still is considered as endangered. Due to its low abundance and the remoteness of its habitat, baseline knowledge on spatio-temporal distribution patterns and behavioural aspects are scarce, yet crucial for the conservation of this population. Long-term passive acoustic recordings were collected at different locations in eastern Fram Strait (78-79°N, 0-7°E), contributing to the Ocean Observing System FRAM (Frontiers in Arctic Marine Monitoring). Data recorded during two sampling periods between 2012 and 2017 were analysed for the occurrence of bowhead whales using the Low-Frequency Detection and Classification System (LFDCS). Seasonal changes in their acoustic repertoire were investigated using recordings from a single year and location. Bowhead whales were acoustically present from autumn throughout winter (October/November-February) and occasionally in spring (March-June), suggesting that Fram Strait is used as an overwintering area. Given that peak levels of acoustic presence coincided with the presumed mating period of bowhead whales, Fram Strait may also serve as a mating area. No bowhead whales were recorded in summer (July-September), indicating that they either were vocally inactive or had migrated to summering areas. Eight distinct song types of bowhead whales were identified comprising simple songs and call sequences. Even though more than one song type was recorded at a given time, there was an overall trend that songs occurred in temporal succession. It remains speculative why songs appeared and subsequently disappeared with the progressing season, but the temporal succession possibly is related to the song types being used in different behavioural contexts. One song type formed an exception as it was recorded throughout almost the entire season and may hence serve a communicative function common to all individuals, or at a least a large part of the population. In contrast to previous studies on bowhead whales in western Fram Strait, the recorded bowhead whale detections were less frequent and, in addition, less complex. Bowhead whales appear to preferentially occupy the western part of Fram Strait where sea ice concentrations are generally higher. Due to the observed regional differences in the acoustic behaviour between eastern and western Fram Strait, eastern Fram Strait may represent the easterly distribution range boundary of the bowhead whale overwintering area. The findings of this study further highlight the importance of Fram Strait as a habitat for the endangered Spitsbergen bowhead whale population. In the light of rapid changes in the Arctic region, an improved understanding of distribution patterns and the acoustic behaviour is of particular relevance for developing effective conservation and management strategies, but also for assessing potential effects on the bowhead whale population resulting from climate-induced environmental changes

Methodik zur Bestimmung optimaler Parameter beim Drahtumformen

Mehrstufige Drahtumformprozesse stellen die fertigungstechnische Grundlage für technisch anspruchsvolle Bauteile dar. Bei diesen mehrstufigen Prozessen ist die Ermittlung der resultierenden Eigenspannungen sowohl analytisch als auch numerisch bisher nur bedingt möglich. Zielsetzung der vorliegenden Arbeit ist die Bereitstellung einer Methodik zur Bestimmung der optimalen Parameter beim Drahtumformen. Als erstes wird die zur Beschreibung des Umformvorgangs nötige Werkstoffcharakterisierung durchgeführt. Diese Charakterisierung basiert auf Experimenten, die sowohl den BAUSCHINGER-Effekt als auch Ver- und Entfestigungsmechanismen untersuchen und quantifizieren. Darauf aufbauend folgt der zweite Teilbereich, die analytische Beschreibung des mehrstufigen Umformprozesses. Durch Anwendung dieses deskriptiven Algorithmus werden sowohl die (Eigen-)Spannungen als auch die elastischen und plastischen Verformungen zu jedem Zeitpunkt des Umformvorgangs bestimmt. Als dritter Teilbereich werden verschiedene Optimierungsalgorithmen mit unterschiedlichen Zielsetzungen für den deskriptiven Algorithmus vorgestellt.Wire forming processes are the basic manufacturing principle for many machine elements like helical springs, wire coils used for wire race bearings and piston rings. In case of low product requirements a one-step, forming process does the forming with sufficiently results. For ambitious products with high operational or fatigue requirements especially related to residual stress and dimensional accuracy, a multi-step forming process is mandatory. Additional, several challenging products are finished by using mechanical chipping, in particular grinding, for best accuracy and surface quality. For these more complex manufacturing forming processes, neither the calculation by FEM nor by analytical calculation delivers satisfactory results for residual stress of bending situation, resulting strain or spring back as well. Especially the dependencies between the succeeding processing steps are not fully included in available calculation methods yet. The present dissertation provides a methodology for determining the ideal parameters for wire forming. For optimizing residual stresses based on spring back or high forming accuracy as well the methodology raises as a suitable tool. The methodology consists of three major parts. First, the material behavior has to be characterized by several selected trials and defined trial proceedings. The trials especially consider the behavior of hardening and softening and the BAUSCHINGER-Effect as well. Finally the mathematical description of the needed material behavior is done. Second part of methodology includes the completely analytical description of multi-step wire forming. Appliance of the algorithm, leads to results of all stress-strain situations of every forming stage in progress. Last part of methodology includes several optimization strategies for this analytical algorithm. Due to specific application, the usage of the right optimization strategy provides the needed manufacturing parameters. Based on these forming parameters respectively best fit results are possible for the chosen forming situation.Drahtumformprozesse, und hier im Speziellen das Rollbiegen bzw. Winden, stellen die fertigungstechnische Grundlage für einige Maschinenelemente wie beispielsweise Schraubenfedern, Drahtringe für Drahtwälzlager oder Kolbenringe dar. Bei Produkten mit geringen Anforderungen an Form und Beanspruchbarkeit findet das Rollbiegen in Form eines einstufigen Umformprozesses statt. Für technisch anspruchsvollere Bauteile hingegen sind Eigenspannungen und Formgenauigkeit für das Betriebsverhalten von Bedeutung, was einen umfangreicheren Herstellungsprozess erfordert. Deshalb wird anstelle des einstufigen Prozesses ein mehrstufiger Umformprozess eingesetzt, da hiermit beispielsweise eine höhere Formgenauigkeit gewährleistet oder die zerspanende Wegnahme von eigenspannungsbehafteten Querschnittsbereichen berücksichtigt werden kann. Bei diesen komplexeren bzw. mehrstufigen Prozessen ist die Ermittlung der resultierenden Eigenspannungen sowohl analytisch als auch numerisch bisher nur bedingt möglich. Insbesondere die Abhängigkeit der aufeinander folgenden Prozessschritte zueinander erfährt nur mangelhafte Beachtung. Zielsetzung der vorliegenden Arbeit ist die Bereitstellung einer Methodik zur Bestimmung der optimalen Parameter beim Drahtumformen, was beispielsweise zur Erzielung günstiger Umformeigenspannungen oder zu einer hohen Formgenauigkeit führt. Diese Methodik als eigentliches Ergebnis beinhaltet im Rahmen der Arbeit drei Teilbereiche. Als erstes wird die zur Beschreibung des Umformvorgangs nötige Werkstoffcharakterisierung durchgeführt. Diese Charakterisierung basiert auf Experimenten, die sowohl den BAUSCHINGER-Effekt als auch Ver- und Entfestigungsmechanismen untersuchen und quantifizieren. Darauf aufbauend folgt der zweite Teilbereich, die analytische Beschreibung des mehrstufigen Umformprozesses. Durch Anwendung dieses deskriptiven Algorithmus werden sowohl die (Eigen-)Spannungen als auch die elastischen und plastischen Verformungen zu jedem Zeitpunkt des Umformvorgangs bestimmt. Als dritter Teilbereich werden verschiedene Optimierungsalgorithmen mit unterschiedlichen Zielsetzungen für den deskriptiven Algorithmus vorgestellt

Testing the usefulness of optical data for zooplankton long‐term monitoring: Taxonomic composition, abundance, biomass, and size spectra from ZooScan image analysis

The pelagic ecosystem of the Arctic Ocean is threatened by severe changes such as the reduction in sea-ice coverage and increased inflow of warmer Atlantic water. The latter is already altering the zooplankton community, highlighting the need for monitoring studies. It is therefore essential to accelerate the taxonomic identification to speed up sample analysis, and to expand the analysis to biomass and size assessments, providing data for modeling efforts. Our case study in Fram Strait illustrates that image-based analyses with the ZooScan provide abundance data and taxonomic resolutions that are comparable to microscopic analyses and are suitable for zooplankton monitoring purposes in the Arctic. We also show that image analysis allows to differentiate developmental stages of the key species Calanus spp. and Metridia longa and, thus, to study their population dynamics. Our results emphasize that older preserved samples can be successfully reanalyzed with ZooScan. To explore the applicability of image parameters for calculating total mesozooplankton and Calanus spp. biomasses, we used (1) conversion factors (CFs) translating wet mass to dry mass (DM), and (2) length–mass (LM) relationships. For Calanus spp., the calculated biomass values yielded similar results as direct DM measurements. Total mesozooplankton biomass ranged between 1.6 and 15 (LM) or 2.4 and 21 (CF) g DM m−2, respectively, which corresponds to previous studies in Fram Strait. Ultimately, a normalized biomass size spectra analysis provides 1st insights into the mesozooplankton size structure at different depths, revealing steep slopes in the linear fit in communities influenced by Atlantic water inflow

Passive acoustic monitoring reveals year-round marine mammal community composition off Tasiilaq, Southeast Greenland

Climate-driven changes are affecting sea ice conditions off Tasiilaq, Southeast Greenland, with implications for marine mammal distributions. Knowledge about marine mammal presence, biodiversity, and community composition is key to effective conservation and management but is lacking, especially during winter months. Seasonal patterns of acoustic marine mammal presence were investigated relative to sea ice concentration at two recording sites between 2014 and 2018, with one (65.6°N, 37.4°W) or three years (65.5°N, 38.0°W) of passive acoustic recordings. Seven marine mammal species were recorded. Bearded seals were acoustically dominant during winter and spring, whereas sperm, humpback, and fin whales dominated during the sea ice-free summer and autumn. Narwhals, bowhead, and killer whales were recorded only rarely. Song-fragments of humpback whales and acoustic presence of fin whales in winter suggest mating-associated behavior taking place in the area. Ambient noise levels in 1/3-octave level bands (20, 63, 125, 500, 1000, and 4000 Hz), ranged between 75.6 to 105 dB re 1 μPa. This study provides multi-year insights into the coastal marine mammal community composition off Southeast Greenland and suggests that the Tasiilaq area provides suitable habitat for various marine mammal species year-round

Acoustic presence and vocal repertoire of bowhead whales (Balaena mysticetus) in eastern and central Fram Strait

Bowhead whales (Balaena mysticetus) 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

Vocal behaviour of bowhead whales (Balaena mysticetus) in eastern Fram Strait

Bowhead whales (Balaena mysticetus) of the East Greenland-Svalbard-Barents Sea (Spitsbergen) population have been depleted close to the point of extinction by commercial whaling and are still considered as endangered. Due to their low abundance and the remoteness of their habitat, baseline knowledge on spatio-temporal distribution patterns and behavioural aspects are scarce, yet crucial for the conservation of this population. Long-term passive acoustic recordings were collected at different locations in 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 analysed for the acoustic occurrence of bowhead whales at an hourly resolution using an automated detector. 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 when bowhead whales were recorded almost daily, often hourly for several days in a row. 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 either were vocally inactive or had migrated to summering areas. Compared to previous studies in western Fram Strait, bowhead whale detections in our recordings were less frequent and less complex. The observed regional differences in bowhead whale acoustic behaviour across Fram Strait suggest that our mooring locations in eastern Fram Strait may represent the eastern distribution boundary of the bowhead whale overwintering area

Frozen verses: Antarctic minke whales (Balaenoptera bonaerensis) call predominantly during austral winter

The recent identification of the bio-duck call as Antarctic minke whale (AMW) vocalization allows the use of passive acoustic monitoring to retrospectively investigate year-round spatial-temporal patterns in minke whale occurrence in ice-covered areas. Here, we present an analysis of AMW occurrence patterns based on a 9-year passive acoustic dataset (2008–2016) from 21 locations throughout the Atlantic sector of the Southern Ocean (Weddell Sea). AMWs were detected acoustically at all mooring locations from May to December, with the highest presence between August and November (bio-duck calls present at more than 80% of days). At the southernmost recording locations, the bio-duck call was present up to 10 months of the year. Substantial inter-annual variation in the seasonality of vocal activity correlated to variation in local ice concentration. Our analysis indicates that part of the AMW population stays in the Weddell Sea during austral winter. The period with the highest acoustic presence in the Weddell Sea (September–October) coincides with the timing of the breeding season of AMW in lower latitudes. The bio-duck call could therefore play a role in mating, although other behavioural functions of the call cannot be excluded to date

Spatio-temporal patterns in acoustic presence and distribution of Antarctic blue whales Balaenoptera musculus intermedia in the Weddell Sea

© 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.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

The marine soundscape off Elephant Island: A Southern Ocean coastal habitat

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

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

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