Nutzung von akustischen Methoden zum Schutz von Schweinswalen (Phocoena phocoena) in deutschen Gewässern

Harbour porpoises Phocoena phocoena in German waters are faced with a variety of different anthropogenic and natural stressors that can have serious effects on population development. Anthropogenic stressors include prey depletion, influences of chemical and pharmaceutical toxins, by-catch in static fishing gear, noise pollution and habitat degradation. Climate influences add to these stressors and may pose both natural as well as anthropogenic threats. Pile-driving noise for construction of offshore wind farms is a new influence that is suspected to have adverse effects on porpoises. Within German waters three subpopulations of porpoises can be found. The North Sea subpopulation extends into the Skagerrak and parts of the Kattegat, the Belt Sea subpopulations reaches from these regions into the waters of the Kiel and Mecklenburg Bight while the Baltic Proper subpopulation has its presumed boundaries at the Darß and Limhamn Sills and populates the waters of the inner Baltic Sea. While the abundance of porpoises in the North Sea seems stable, this has been questioned for the Belt Sea subpopulation. The Baltic Proper subpopulation is recognized as ‘critically endangered’ by the IUCN (International Union for Conservation of Nature) red list and surveys within the last decades have not lead to conclusive abundance estimates due to the scarcity of sightings. Within this study Stationary Acoustic Monitoring (SAM) with echolocation click loggers (T-PODs – Timing Porpoise Detectors and C-PODs – Cetacean PODs, both Chelonia Ltd., UK) was used to describe distribution patterns of porpoises and analyse factors driving acoustic presence of porpoises in German waters. Harbour porpoises use echolocation almost constantly and hence registrations on the loggers represent a relative measure for porpoise presence in an area. This relatively new method is still developing rapidly and neither analysis strategies nor devices are standardized as has been done for other assessment methods. However, when using these devices for monitoring, effect monitoring and other long-term studies, it is essential to standardize the instruments, as well as to develop standard procedures for data evaluation. To account for variability of the loggers, a rigorous calibration of the instruments was conducted prior to field trials and repeatedly over time. The results indicate that the older T-PODs (Chelonia Ltd., UK) had a wide variation in detection thresholds at the beginning of the study, but newer versions were found to be well standardized. For C-PODs (Chelonia Ltd., UK), the digital successor of the T-POD, the calibration showed a much better standardization at the preferred porpoise vocalisation frequency of 130 kHz. Other frequencies were less comparable indicating that surveys for species using lower frequencies must obtain calibration data for their instruments. The first long-term deployment of up to 42 T-PODs in the German Baltic Sea documented strong geographical and seasonal differences in porpoise occurrence. Instruments deployed closer together gathered more comparable data than devices further away. This indicates that these differences represent a genuine occurrence pattern with higher detection rates in westerly waters, which gradually decrease towards the Pomeranian Bay in the east. Overall, more porpoises were registered from spring to fall, indicating a possible relationship to herring as one preferred prey item. A second long-term study was conducted to analyse the echolocation behaviour of porpoises east of the Darß and south of the Limhamn Sill. Detection rates showed two peaks in seasonal occurrence of porpoises at these sites. This result indicates most likely that porpoises from both subpopulations in German waters use the area of the Pomeranian Bay in an alternating pattern of habitat use: porpoises from the Belt Sea distribute throughout German waters from spring to fall, with maximum detection rates in summer, while Baltic Proper porpoises use the area during winter to avoid suffocation in the closed ice cover in the inner Baltic waters. The modelling indicated that salinity was a significant factor for presumed Belt Sea animals, while temperature had significant influences on all detection rates. To estimate the impact of pile-driving noise on porpoises a third long-term study was conducted off the German coast close to Borkum Reefground, where the first German offshore wind farm alpha ventus was constructed from 2008 to 2009. Visual observations showed a strong displacement of porpoises during pile-driving out to a distance of ~20 km around the pile-driving site during a survey exactly timed to the piling activities. Acoustic monitoring showed reduced detection rates close to the pile-driving operation in distances up to 11 km. There were no stations between 11 and 23 km distance. At 25 and 50 km distance detection rates increased indicating that porpoises were possibly displaced towards these positions and hence a behavioural reaction was recorded outside of the displacement radius. Furthermore, the duration of porpoise absence during and after pile-driving was correlated with the duration of pile-driving. From this data it remained unclear whether the displacement process was fully completed. To mitigate effects, such as described for the construction of alpha ventus, more work is necessary to find suitable noise mitigation measures. In a previous project it was shown that a stacked bubble curtain greatly reduced the sound levels, as well as the behavioural reaction in captive porpoises during harbour construction work in Denmark. In a follow up project it was tested which factors actually led to the large attenuation and how different nozzle layouts in a test tank environment under controlled conditions lead to changed attenuation rates. A second test of a single system was carried out in Kiel harbour. For both of these trials an underwater loudspeaker served as the sound source and modulated sine wave impulses were used to test attenuation efficacy. The resulting attenuation rates were much larger than previously reported. This is most probably linked to the sound source that was used in these experiments, which does not behave like a pile being driven. The pile is a line source with contact to three media: air, water and sediment. We tested only the water transmission path in these experiments. However, transmission through the sediment may play a large role in offshore conditions and must be accounted for within future offshore construction work.Schweinswale Phocoena phocoena in deutschen Gewässern sind verschiedenen anthropogenen und natürlichen Stressoren ausgesetzt, die erhebliche Auswirkungen auf die Populationsentwicklung haben können. Dazu gehören vermindertes Beutevorkommen, Einflüsse von chemischen und pharmazeutischen Toxinen, Beifang in stationären Netzen der Fischerei, Schalleinflüsse und Habitatveränderungen. Weiterhin kommen klimatische Einflüsse hinzu, die sowohl als natürliche als auch als anthropogene Gefährdungen betrachtet werden können. Ein neuer potentiell schädlicher Einfluss für Schweinswale sind Rammgeräusche während der Errichtung von Fundamenten für Offshore-Windparks. In den deutschen Gewässern kommen drei Subpopulationen von Schweinswalen vor. Die Nordsee-Subpopulation kommt ebenfalls in den Gewässern des Skagerraks und zum Teil im Kattegat vor. Die Beltsee-Subpopulation erstreckt sich von dort bis in die Gewässer der Kieler und Mecklenburger Bucht. Die innere Ostsee-Subpopulation hat vermutlich ihre Verbreitungsgrenze an der Darßer und Limhamn-Schwelle und bevölkert die innere Ostsee. Während die Abundanz von Schweinswalen in der Nordsee stabil erscheint, ist dies für die Beltsee-Subpopulation fraglich. Die Subpopulation der inneren Ostsee wird durch die rote Liste der IUCN (International Union for Conservation of Nature) als‚ vom Aussterben bedroht‘ eingestuft. Erfassungen in den letzten Jahrzehnten haben nicht zu belastbaren Bestandszahlen geführt. In dieser Studie wurde Stationäres Akustisches Monitoring (SAM) mit Echoortungsklickloggern (T-PODs – Timing POrpoise Detectors und C-PODs – Cetaceen PODs, beide Chelonia Ltd., UK) eingesetzt, um Aufenthaltsmuster von Schweinswalen zu analysieren und Faktoren zu ermitteln, die die akustische Präsenz von Schweinswalen in deutschen Gewässern beeinflussen. Schweinswale nutzen Echoortung fortwährend und somit entsprechen die Registrierungsraten der Logger (akustische Präsenz) einem relativen Maß für die Anwesenheit von Schweinswalen in diesem Areal. Die relativ neue Methode entwickelt sich derzeit schnell weiter, wobei weder die genutzten Maßeinheiten, noch die Geräte einer generellen Standardisierung unterliegen, wie es für andere Erfassungsmethoden üblich ist. Eine Standardisierung der Geräte und der Auswertungsmethoden zu entwickeln ist unerlässlich, um die Geräte für ein Monitoring, Effektmonitoring oder für andere Langzeitstudien einzusetzen. Eine Kalibrierung der Messgeräte wurde vor den Feldversuchen und in regelmäßigen Abständen wiederholt, um individuelle Unterschiede der Logger zu berücksichtigen. Die Ergebnisse zeigen, dass ältere T-PODs eine große Variation in der Detektionsschwelle zu Beginn der Erfassungen aufwiesen, während neuere Versionen gut standardisiert waren. Für C-PODs zeigte die Kalibrierung eine wesentlich bessere Standardisierung für das von Schweinswalen genutzte Frequenzband um 130 kHz. Andere Frequenzen zeigten weniger vergleichbare Ergebnisse. Dies hat zur Folge, dass für Erfassungen von anderen Walarten mit einer geringeren Vokalisationsfrequenz die Geräte separat kalibriert werden müssen. Starke saisonale und geografische Unterschiede konnten durch die erste Langzeiterfassung in der deutschen Ostsee mit 42 T-PODs gezeigt werden. Geräte mit einem geringeren geografischen Abstand nahmen dabei ähnlichere Daten auf, als solche mit größeren Abständen. Die aufgezeichneten Unterschiede der akustischen Daten spiegeln somit höchstwahrscheinlich korrekte Aufenthaltsmuster wieder. In westlichen Bereichen der deutschen Ostsee wurden höheren Registrierungsraten abnehmend zur Pommerschen Bucht im Osten festgestellt. Es wurden vermehrt Schweinswale im Zeitraum von Frühling bis Herbst registriert. Dies könnte im Zusammenhang mit dem Vorkommen von Hering, einer bevorzugten Beuteart, stehen. Eine zweite Langzeitstudie wurde durchgeführt, um das Echoortungsverhalten von Schweinswalen östlich der Darßer und südlich der Limhamn-Schwelle zu analysieren. Die Ergebnisse zeigen zwei saisonale Maxima der Schweinswalregistrierungsraten. Schweinswale beider Subpopulationen könnten somit die Gewässer der Pommerschen Bucht alternierend nutzen: Schweinswale der Beltsee-Subpopulation breiten sich von Frühling bis Herbst in deutschen Gewässern aus, mit maximalen Detektionsraten im Sommer, während die innere Ostsee-Subpopulation diese Bereiche im Winter nutzt, um der Erstickungsgefahr unter einer geschlossenen Eisdecke in der inneren Ostsee zu entgehen. Die Modellierung zeigt weiterhin, das Salinität ein wichtiger Faktor für die Registrierungsraten von Schweinswalen in der Beltsee ist, während Temperatur einen hohen Einfluss auf die Registrierungsraten aller Stationen hatte. Um den Einfluss von Rammgeräuschen auf Schweinswale zu ermitteln wurde eine dritte Langzeitstudie vor der deutschen Küste nahe Borkum Riffgrund durchgeführt, wo der erste deutsche Windpark alpha ventus von 2008 bis 2009 errichtet wurde. Visuelle Beobachtungen zeigen eine starke Fluchtreaktion der Schweinswale während der Rammarbeiten in ca. ~20 km Radius um die Baustelle während eines Surveys auf, der exakt zeitgleich mit den Rammarbeiten absolviert wurde. Das akustische Monitoring zeigte reduzierte Registrierungsraten bis in 11 km Distanz. In den Entfernungen zwischen 11 und 23 km waren keine Messinstrumente ausgebracht. In 25 und 50 km Entfernung waren die Detektionsraten erhöht. Dies deutet darauf hin, dass Schweinswale zu diesen Stationen vertrieben wurden. Dementsprechend konnte eine Verhaltensreaktion von Schweinswalen in einem wesentlich größeren Bereich nachgewiesen werden, als der Vertreibungsradius indiziert. Außerdem war die Länge der Abwesenheit von Schweinswalen während und nach der Rammung mit der Dauer der Rammarbeiten korreliert. Aus den aufgezeichneten Daten ist nicht ersichtlich, ob der Vertreibungsvorgang vollständig abgeschlossen war. Um die bei alpha ventus nachgewiesenen Effekte abzumindern ist weitere Forschung notwendig, um geeignete Schallminderungsmethoden zu finden. In einem Vorgängerprojekt wurde gezeigt, dass ein gestufter Luftblasenschleier die Schallpegel, aber auch die Verhaltensreaktionen von Schweinswalen in Gefangenschaft während Hafenbauarbeiten in Dänemark stark reduzierte. Im hier vorgestellten Folgeprojekt wurde getestet, welche Faktoren zu dieser starken Reduktion der Lautstärke von Rammarbeiten geführt haben und wie verschiedene Luftdüsenlayouts sich in einem Laborversuch unter kontrollierten Bedingen auf die Effektivität der Abschwächung auswirken. Ein Feldversuch eines Einzelsystems wurde im Kieler Hafen durchgeführt. Für beide Tests wurden Unterwasserlautsprecher als Schallquelle genutzt, die modulierte Sinussignale bei definierten Testfrequenzen aussandten. Die innerhalb der Tests gemessene Abschwächung war wesentlich größer, als bisher berichtet wurde. Dies ist höchstwahrscheinlich durch den Lautsprecher als verwendete Schallquelle zu erklären, der sich akustisch nicht wie ein gerammter Pfahl verhält. Der Pfahl ist eine Linienquelle, die im Kontakt mit drei verschiedenen Medien steht: Luft, Wasser und Sediment. Von diesen drei Pfaden wurde somit innerhalb der Experimente nur die Wasserschallausbreitung getestet. Dementsprechend könnte die Schallausbreitung durch das Sediment eine größere Rolle unter reellen Offshore-Bedingungen spielen und muss für zukünftige Bauvorhaben mit betrachtet werden

User-centered design in brain–computer interfaces — a case study

The array of available brain–computer interface (BCI) paradigms has continued to grow, and so has the corresponding set of machine learning methods which are at the core of BCI systems. The latter have evolved to provide more robust data analysis solutions, and as a consequence the proportion of healthy BCI users who can use a BCI successfully is growing. With this development the chances have increased that the needs and abilities of specific patients, the end-users, can be covered by an existing BCI approach. However, most end-users who have experienced the use of a BCI system at all have encountered a single paradigm only. This paradigm is typically the one that is being tested in the study that the end-user happens to be enrolled in, along with other end-users. Though this corresponds to the preferred study arrangement for basic research, it does not ensure that the end-user experiences a working BCI. In this study, a different approach was taken; that of a user-centered design. It is the prevailing process in traditional assistive technology. Given an individual user with a particular clinical profile, several available BCI approaches are tested and – if necessary – adapted to him/her until a suitable BCI system is found

High-Fidelity-based MDO: A Closer Look at the Selected Sub-Processes Overall Aircraft Design Synthesis, Loads Analysis, and Structural Optimization

Within the DLR project VicToria various high fidelity-based MDO processes were set-up as applicalble methods for aircraft design. Apart from aerodynamic optimization using high fidelity-based CFD analysis, the sub-processes overall aircraft design synthesis, loads analysis, and structural optimization were part of the MDO processes. The presented paper expounds such MDO sub-processes in order to exhibit their contributions and capabilities for the respected MDO process

Rapid transformation of lamination parameters into stacking sequences

Lamination parameter optimisation is a highly efficient type of composite optimisation. An equally efficient transformation of lamination parameters into stacking sequences is not yet available. This paper presents a general method for rapidly transforming lamination parameters into continuous stacking sequences. Systematic studies of the relationship between lamination parameters and stacking sequences provide a broad understanding of the transformation problem. An important finding is that multiple stacking sequences share the same lamination parameter set. The transformation is therefore not unique and has to account for multiple layup solutions. The layup retrieval algorithm uses primitive optimisation techniques to search for all optima in the layup space. Ply angles and layer numbers are hereby not restricted. In two representative examples, the authors show the algorithm's capabilities of finding all stacking sequence solutions of a twelve layer laminate and of finding multiple stacking sequence solutions for arbitrary layer numbers. This makes the algorithm applicable for stacking sequence retrieval, the last step in lamination parameter optimisation

Variation of blubber thickness for three marine mammal species in the southern Baltic Sea

Evaluating populational trends of health condition has become an important topic for marine mammal populations under the Marine Strategy Framework Directive (MSFD). In the Baltic Sea, under the recommendation of Helsinki Commission (HELCOM), efforts have been undertaken to use blubber thickness as an indicator of energy reserves in marine mammals. Current values lack geographical representation from the entire Baltic Sea area and a large dataset is only available for grey seals (Halichoerus grypus) from Sweden and Finland. Knowledge on variation of blubber thickness related to geography throughout the Baltic Sea is important for its usage as an indicator. Such evaluation can provide important information about the energy reserves, and hence, food availability. It is expected that methodological standardization under HELCOM should include relevant datasets with good geographical coverage that can also account for natural variability in the resident marine mammal populations. In this study, seasonal and temporal trends of blubber thickness were evaluated for three marine mammal species—harbor seal (Phoca vitulina), grey seal (Halichoerus grypus) and harbor porpoise (Phocoena phocoena)—resident in the southern Baltic Sea collected and investigated under stranding networks. Additionally, the effects of age, season and sex were analyzed. Seasonal variation of blubber thickness was evident for all species, with harbor seals presenting more pronounced effects in adults and grey seals and harbor porpoises presenting more pronounced effects in juveniles. For harbor seals and porpoises, fluctuations were present over the years included in the analysis. In the seal species, blubber thickness values were generally higher in males. In harbor seals and porpoises, blubber thickness values differed between the age classes: while adult harbor seals displayed thicker blubber layers than juveniles, the opposite was observed for harbor porpoises. Furthermore, while an important initial screening tool, blubber thickness assessment cannot be considered a valid methodology for overall health assessment in marine mammals and should be complemented with data on specific health parameters developed for each speciesinfo:eu-repo/semantics/publishedVersio

Time and tide : seasonal, diel and tidal rhythms in Wadden Sea Harbour porpoises (Phocoena phocoena)

The study was partly funded by the Schleswig-Holstein’s Government-Owned Company for Coastal Protection, National Parks and Ocean Protection, Wadden Sea National Park Administration of Lower Saxony (Richard Czeck) and the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (FKZ: 03 275 20 and FKZ: 0329946B). This publication was supported by Deutsche Forschungsgemeinschaft and University of Veterinary Medicine Hannover, Foundation within the funding programme Open Access Publishing.Odontocetes have evolved a rich diversity of prey- and habitat-specific foraging strategies, which allows them to feed opportunistically on locally and temporally abundant prey. While habitat-specific foraging strategies have been documented for some odontocete species, this is less known for the harbour porpoise (Phocoena phocoena). We collected multiple years of acoustic data using echolocation click loggers to analyse porpoise occurrence and buzzing behaviour, indicating feeding, in the German Wadden Sea (North Sea). Seasonal, diel and tidal effects were studied using Generalised Estimating Equations (GEE-GAMs). Locally season, time of day and tidal time significantly influenced the probability of porpoise detections and detection of foraging sequences (buzzes). Hunting strategies, and therefore frequency of buzzes, were likely affected by prey distribution and large differences between POD locations indicated that porpoises used highly specific behaviour adapted to tide and time of day to efficiently feed on the available prey. Strong seasonal and spatial variation in diel and tidal effects underline the importance of long-term observations. Studies on porpoise behaviour are often based on short-term observations and might rather reflect a seasonal than a general pattern. The results of this study show clearly that significant changes in porpoise behaviour can be found in short and long-term observations. Here some features are based on short term determinants and others are stable over years and care should be taken about drawing general conclusions based on local patterns. Highly variable spatio-temporal patterns indicate a high flexibility of porpoises in a highly variable environment and address a challenge for complex conservation management plans.Publisher PDFPeer reviewe

Estimating the abundance of the critically endangered Baltic Proper harbour porpoise (Phocoena phocoena) population using passive acoustic monitoring

The SAMBAH project was funded by the LIFE+ program of the European Commission (LIFE08 NAT/S/000261) and co-funded by Bundesamt für Naturschutz, Germany (SAMBAH II 5 Vw/52602/2011-Mar 36032/66); Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit, Germany (COSAMM FKZ 0325238); Carlsbergfondet, Denmark (CF16-0861); European Association of Zoos and Aquaria, The Netherlands; Główny Inpektorat Ochrony Środowiska, Poland; Havs-och Vattenmyndigheten, Sweden; Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy, Poland; Japanese Science and Technology Agency-CREST, Japan (7620-7); Kolmårdens Djurpark, Sweden; Maailman Luonnon Säätiö (WWF) Suomen Rahasto, Finland; Miljøministeriet, Denmark; Miljø- og Fødevareministeriet, Denmark (SN 343/SN-0008); Narodowy Fundusz Ochrony Środowiska i Gospodarki Wodnej, Poland (561/2009/Wn-50/OP/RE-LF/D); Naturvårdsverket, Sweden; SNAK Ph.D. School, Aarhus University, Denmark (91147/365); Tampereen Särkänniemi Ltd., Finland; Turun ammattikorkeakoulu Oy, Finland; Uniwersytet Gdański, Poland; Wojewódzki Fundusz Ochrony Środowiska i Gospodarki Wodnej w Gdańsku, Poland; and Ympäristöministeriö, Finland.Knowing the abundance of a population is a crucial component to assess its conservation status and develop effective conservation plans. For most cetaceans, abundance estimation is difficult given their cryptic and mobile nature, especially when the population is small and has a transnational distribution. In the Baltic Sea, the number of harbour porpoises (Phocoena phocoena) has collapsed since the mid-20th century and the Baltic Proper harbour porpoise is listed as Critically Endangered by the IUCN and HELCOM; however, its abundance remains unknown. Here, one of the largest ever passive acoustic monitoring studies was carried out by eight Baltic Sea nations to estimate the abundance of the Baltic Proper harbour porpoise for the first time. By logging porpoise echolocation signals at 298 stations during May 2011-April 2013, calibrating the loggers' spatial detection performance at sea, and measuring the click rate of tagged individuals, we estimated an abundance of 71-1105 individuals (95% CI, point estimate 491) during May-October within the population's proposed management border. The small abundance estimate strongly supports that the Baltic Proper harbour porpoise is facing an extremely high risk of extinction, and highlights the need for immediate and efficient conservation actions through international cooperation. It also provides a starting point in monitoring the trend of the population abundance to evaluate the effectiveness of management measures and determine its interactions with the larger neighboring Belt Sea population. Further, we offer evidence that design-based passive acoustic monitoring can generate reliable estimates of the abundance of rare and cryptic animal populations across large spatial scales.Publisher PDFPeer reviewe

Fatty Acid Composition in Blubber, Liver, and Muscle of Marine Mammals in the Southern Baltic Sea

Marine mammals play an important role in marine ecosystems. However, as they are less accessible for research, relatively little is known about their physiology compared to terrestrial mammals. The stranding scheme of the Deutsches Meeresmuseum (Stralsund, Germany) continuously collects strandings and by-catches of marine mammals in the Baltic Sea in Mecklenburg-Western Pomerania. In this project, the fatty acid composition of the liver, skeletal muscles, and blubber of harbour porpoises and grey seals from the southern Baltic Sea was investigated for the first time. In the liver and blubber tissue, the values and concentrations measured for both species are consistent with studies on other marine mammals. In a direct comparison of the focus species, the skeletal muscles of harbour porpoises exhibit higher concentrations of fatty acids than those of grey seals. In the future, these studies will be extended to the entire Baltic Sea, as we suspect that fatty acid composition can be used to determine the nutritional status of the animals and thus will allow for an objective assessment of the body condition.Peer Reviewe