To date, only limited results on the fatty composition in different tissues of the top predators ... more To date, only limited results on the fatty composition in different tissues of the top predators in the Baltic Sea are available. In the current study, tissue samples of blubber, skeletal muscle, and liver from 8 harbour porpoise (Phocoena phocoena) and 17 grey seals (Halichoerus grypus) in the Baltic Sea off Mecklenburg-Western Pomerania were included in the investigation. While the total fatty acid content in liver and blubber tissue revealed no differences between both species, the total fatty acid content of muscle tissue was significantly differentand showed higher concentrations in harbour porpoise muscle compared with grey seals. The most abundant fatty acids in the blubber of grey seals and harbour porpoises (18:1cis-9, 16:1cis-9, 16:0 and 22:6n-3) were present in similar quantities and ratios to each other as known from other marine top predators. If future studies can show that differences in tissue fatty acid content are caused by variation in the nutritional status, and ...
The Journal of the Acoustical Society of America, 2017
A key question related to regulating noise from pile driving, air guns, and sonars is how to take... more A key question related to regulating noise from pile driving, air guns, and sonars is how to take into account the hearing abilities of different animals by means of auditory frequency weighting. Recordings of pile driving sounds, both in the presence and absence of a bubble curtain, were evaluated against recent thresholds for temporary threshold shift (TTS) for harbor porpoises by means of four different weighting functions. The assessed effectivity, expressed as time until TTS, depended strongly on choice of weighting function: 2 orders of magnitude larger for an audiogram-weighted TTS criterion relative to an unweighted criterion, highlighting the importance of selecting the right frequency weighting.
The Journal of the Acoustical Society of America, Jul 1, 2016
Testing the hearing abilities of marine mammals under water is a challenging task. Sample sizes a... more Testing the hearing abilities of marine mammals under water is a challenging task. Sample sizes are usually low, thus limiting the ability to generalize findings of susceptibility towards noise influences. A method to measure harbor porpoise hearing thresholds in situ in outdoor conditions using auditory steady state responses of the brainstem was developed and tested. The method was used on 15 live-stranded animals from the North Sea during rehabilitation, shortly before release into the wild, and on 12 wild animals incidentally caught in pound nets in Denmark (inner Danish waters). Results indicated that although the variability between individuals is wide, the shape of the hearing curve is generally similar to previously published results from behavioral trials. Using 10-kHz frequency intervals between 10 and 160 kHz, best hearing was found between 120 and 130 kHz. Additional testing using one-third octave frequency intervals (from 16 to 160 kHz) allowed for a much faster hearing...
Advances in experimental medicine and biology, 2016
The project conducts application-oriented research on impacts of underwater noise on marine verte... more The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise from pile driving and stress reactions caused by anthropogenic noise is investigated. Animals are equipped with DTAGs capable of recording the actual surrounding noise field of free-swimming harbor porpoises and seals. Acoustic noise mapping including porpoise detectors in the Natura 2000 sites of the North and Baltic Seas will help to fully understand current noise impacts.
Before, during and after the construction of alpha ventus a comprehensive monitoring was carried ... more Before, during and after the construction of alpha ventus a comprehensive monitoring was carried out using visual line transect sampling along with continuous static acoustic monitoring to investigate possible short- and long-term impacts of alpha ventus on harbour porpoises. The seasonal and spatial distribution of porpoises were analysed by dedicated aerial surveys in a study area of almost 11,000 km2 while the habitat use and behaviour were investigated with 12 echolocation loggers. We showed that the effect of the short-term construction period had an impact over large distances as detection rates decreased in less than 10.8 km and increased in larger distances to alpha ventus, suggesting that porpoises were displaced towards these positions. Here, we will focus on data of the operating period and place results in the context of general distribution trends. The operation period most likely has a small spatial scale impact where effects could either be attributable to noise or to...
Ecological Research at the Offshore Windfarm alpha ventus, 2014
ABSTRACT Offshore windfarms have the potential to affect marine mammal populations. For harbour p... more ABSTRACT Offshore windfarms have the potential to affect marine mammal populations. For harbour porpoises, the threat considered most important is the influence of noise during the construction phase. Effects of the operational period that need to be considered can be either noise effects or effects due to alteration to the habitat where foundations were erected. Visual surveys and stationary acoustic monitoring showed a strong avoidance reaction during pile-driving while during the operational period results were inconclusive. In future, these impacts must be seen in a larger framework to predict the biological significance of cumulative effects.
Journal of the Marine Biological Association of the UK, 2007
The harbour porpoise is the only resident cetacean species in the German Baltic Sea. Within the l... more The harbour porpoise is the only resident cetacean species in the German Baltic Sea. Within the last several decades this harbour porpoise stock declined drastically, causing deep concern about its status. Plans of the German government for proposing Marine Protected Areas (MPAs) to implement Natura 2000 and for assessing the impact of offshore windmill constructions on the marine environment led to an increased research effort on the harbour porpoise in German waters. For the first time, long-term passive acoustic monitoring has been conducted in the German Baltic Sea from the Kiel Bight to the Pomeranian Bay from August 2002 to December 2005. Porpoise detectors (T-PODs) have been installed five to seven metres below the water surface at up to 42 measuring positions throughout the investigated area, registering the exact times of echolocation signals of passing harbour porpoises. The proportion of monitored days with porpoise detection in each quarter of the years has been analysed...
The Journal of the Acoustical Society of America, 2013
Static acoustic monitoring (SAM) is one major technology for observing small cetacean species. Au... more Static acoustic monitoring (SAM) is one major technology for observing small cetacean species. Automatic click loggers deployed for long time periods (>2 months) with a single hydrophone are a standard solution. Acoustic properties, like detection thresholds of these instruments, are essential for interpretation of results, but have nevertheless received little attention. A methodology for calibrating tonal click detectors in small tanks consisting of the determination of the horizontal directivity pattern and detection thresholds including a transfer function is presented. Two approaches were tested to determine detection thresholds by (a) determining the 50% detection threshold and (b) fitting a linear regression model to the recorded relative amplitudes. The tests were carried out on C-PODs (Cetacean PODs, tonal click detectors), the most commonly used instrument for SAM in Europe. Directivity and threshold were tested between 60 and 150 kHz. Directivity showed a maximum variation of 8.5 dB in the horizontal plane. Sensitivity is highest between 80 and 130 kHz and linear (± 3 dB) in this frequency range for most of the instruments tested. C-PODs have a detection threshold (calculated with the linear model) of 114.5 ± 1.2 (standard deviation) dB re 1 μPa peak-peak at 130 kHz.
The Journal of the Acoustical Society of America, 2013
Timing Porpoise Detectors (T-PODs, Chelonia Ltd.) are autonomous passive acoustic devices for mon... more Timing Porpoise Detectors (T-PODs, Chelonia Ltd.) are autonomous passive acoustic devices for monitoring odontocetes. They register the time of occurrence and duration of high frequency pulsed sounds as possible odontocetes echolocation clicks. Because of evolution, five T-POD versions exist. Although the manufacturer replaced those by a digital successor, the C-POD, T-PODs are still used, and data from many field studies exist. Characterizing the acoustic properties of T-PODs enables the interpretation of data obtained with different devices. Here, the detection thresholds of different T-POD versions for harbor porpoise clicks were determined. While thresholds among devices were quite variable in the first T-POD generations, they became more standardized in newer versions. Furthermore, the influence of user-controlled settings on the threshold was investigated. From version 3 on, the detection threshold was found to be easily adjustable with version-dependent setting options "minimum intensity" and "sensitivity," enabling the presetting of standard thresholds. In version 4, the setting "click bandwidth" had a strong influence on the detection threshold, while "selectivity" in version 3 and "noise adaptation = ON" or "OFF" in version 4 hardly influenced thresholds obtained in the tank tests. Nevertheless, the latter setting may influence thresholds in a complex acoustic environment like the sea.
To date, only limited results on the fatty composition in different tissues of the top predators ... more To date, only limited results on the fatty composition in different tissues of the top predators in the Baltic Sea are available. In the current study, tissue samples of blubber, skeletal muscle, and liver from 8 harbour porpoise (Phocoena phocoena) and 17 grey seals (Halichoerus grypus) in the Baltic Sea off Mecklenburg-Western Pomerania were included in the investigation. While the total fatty acid content in liver and blubber tissue revealed no differences between both species, the total fatty acid content of muscle tissue was significantly differentand showed higher concentrations in harbour porpoise muscle compared with grey seals. The most abundant fatty acids in the blubber of grey seals and harbour porpoises (18:1cis-9, 16:1cis-9, 16:0 and 22:6n-3) were present in similar quantities and ratios to each other as known from other marine top predators. If future studies can show that differences in tissue fatty acid content are caused by variation in the nutritional status, and ...
The Journal of the Acoustical Society of America, 2017
A key question related to regulating noise from pile driving, air guns, and sonars is how to take... more A key question related to regulating noise from pile driving, air guns, and sonars is how to take into account the hearing abilities of different animals by means of auditory frequency weighting. Recordings of pile driving sounds, both in the presence and absence of a bubble curtain, were evaluated against recent thresholds for temporary threshold shift (TTS) for harbor porpoises by means of four different weighting functions. The assessed effectivity, expressed as time until TTS, depended strongly on choice of weighting function: 2 orders of magnitude larger for an audiogram-weighted TTS criterion relative to an unweighted criterion, highlighting the importance of selecting the right frequency weighting.
The Journal of the Acoustical Society of America, Jul 1, 2016
Testing the hearing abilities of marine mammals under water is a challenging task. Sample sizes a... more Testing the hearing abilities of marine mammals under water is a challenging task. Sample sizes are usually low, thus limiting the ability to generalize findings of susceptibility towards noise influences. A method to measure harbor porpoise hearing thresholds in situ in outdoor conditions using auditory steady state responses of the brainstem was developed and tested. The method was used on 15 live-stranded animals from the North Sea during rehabilitation, shortly before release into the wild, and on 12 wild animals incidentally caught in pound nets in Denmark (inner Danish waters). Results indicated that although the variability between individuals is wide, the shape of the hearing curve is generally similar to previously published results from behavioral trials. Using 10-kHz frequency intervals between 10 and 160 kHz, best hearing was found between 120 and 130 kHz. Additional testing using one-third octave frequency intervals (from 16 to 160 kHz) allowed for a much faster hearing...
Advances in experimental medicine and biology, 2016
The project conducts application-oriented research on impacts of underwater noise on marine verte... more The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise from pile driving and stress reactions caused by anthropogenic noise is investigated. Animals are equipped with DTAGs capable of recording the actual surrounding noise field of free-swimming harbor porpoises and seals. Acoustic noise mapping including porpoise detectors in the Natura 2000 sites of the North and Baltic Seas will help to fully understand current noise impacts.
Before, during and after the construction of alpha ventus a comprehensive monitoring was carried ... more Before, during and after the construction of alpha ventus a comprehensive monitoring was carried out using visual line transect sampling along with continuous static acoustic monitoring to investigate possible short- and long-term impacts of alpha ventus on harbour porpoises. The seasonal and spatial distribution of porpoises were analysed by dedicated aerial surveys in a study area of almost 11,000 km2 while the habitat use and behaviour were investigated with 12 echolocation loggers. We showed that the effect of the short-term construction period had an impact over large distances as detection rates decreased in less than 10.8 km and increased in larger distances to alpha ventus, suggesting that porpoises were displaced towards these positions. Here, we will focus on data of the operating period and place results in the context of general distribution trends. The operation period most likely has a small spatial scale impact where effects could either be attributable to noise or to...
Ecological Research at the Offshore Windfarm alpha ventus, 2014
ABSTRACT Offshore windfarms have the potential to affect marine mammal populations. For harbour p... more ABSTRACT Offshore windfarms have the potential to affect marine mammal populations. For harbour porpoises, the threat considered most important is the influence of noise during the construction phase. Effects of the operational period that need to be considered can be either noise effects or effects due to alteration to the habitat where foundations were erected. Visual surveys and stationary acoustic monitoring showed a strong avoidance reaction during pile-driving while during the operational period results were inconclusive. In future, these impacts must be seen in a larger framework to predict the biological significance of cumulative effects.
Journal of the Marine Biological Association of the UK, 2007
The harbour porpoise is the only resident cetacean species in the German Baltic Sea. Within the l... more The harbour porpoise is the only resident cetacean species in the German Baltic Sea. Within the last several decades this harbour porpoise stock declined drastically, causing deep concern about its status. Plans of the German government for proposing Marine Protected Areas (MPAs) to implement Natura 2000 and for assessing the impact of offshore windmill constructions on the marine environment led to an increased research effort on the harbour porpoise in German waters. For the first time, long-term passive acoustic monitoring has been conducted in the German Baltic Sea from the Kiel Bight to the Pomeranian Bay from August 2002 to December 2005. Porpoise detectors (T-PODs) have been installed five to seven metres below the water surface at up to 42 measuring positions throughout the investigated area, registering the exact times of echolocation signals of passing harbour porpoises. The proportion of monitored days with porpoise detection in each quarter of the years has been analysed...
The Journal of the Acoustical Society of America, 2013
Static acoustic monitoring (SAM) is one major technology for observing small cetacean species. Au... more Static acoustic monitoring (SAM) is one major technology for observing small cetacean species. Automatic click loggers deployed for long time periods (>2 months) with a single hydrophone are a standard solution. Acoustic properties, like detection thresholds of these instruments, are essential for interpretation of results, but have nevertheless received little attention. A methodology for calibrating tonal click detectors in small tanks consisting of the determination of the horizontal directivity pattern and detection thresholds including a transfer function is presented. Two approaches were tested to determine detection thresholds by (a) determining the 50% detection threshold and (b) fitting a linear regression model to the recorded relative amplitudes. The tests were carried out on C-PODs (Cetacean PODs, tonal click detectors), the most commonly used instrument for SAM in Europe. Directivity and threshold were tested between 60 and 150 kHz. Directivity showed a maximum variation of 8.5 dB in the horizontal plane. Sensitivity is highest between 80 and 130 kHz and linear (± 3 dB) in this frequency range for most of the instruments tested. C-PODs have a detection threshold (calculated with the linear model) of 114.5 ± 1.2 (standard deviation) dB re 1 μPa peak-peak at 130 kHz.
The Journal of the Acoustical Society of America, 2013
Timing Porpoise Detectors (T-PODs, Chelonia Ltd.) are autonomous passive acoustic devices for mon... more Timing Porpoise Detectors (T-PODs, Chelonia Ltd.) are autonomous passive acoustic devices for monitoring odontocetes. They register the time of occurrence and duration of high frequency pulsed sounds as possible odontocetes echolocation clicks. Because of evolution, five T-POD versions exist. Although the manufacturer replaced those by a digital successor, the C-POD, T-PODs are still used, and data from many field studies exist. Characterizing the acoustic properties of T-PODs enables the interpretation of data obtained with different devices. Here, the detection thresholds of different T-POD versions for harbor porpoise clicks were determined. While thresholds among devices were quite variable in the first T-POD generations, they became more standardized in newer versions. Furthermore, the influence of user-controlled settings on the threshold was investigated. From version 3 on, the detection threshold was found to be easily adjustable with version-dependent setting options "minimum intensity" and "sensitivity," enabling the presetting of standard thresholds. In version 4, the setting "click bandwidth" had a strong influence on the detection threshold, while "selectivity" in version 3 and "noise adaptation = ON" or "OFF" in version 4 hardly influenced thresholds obtained in the tank tests. Nevertheless, the latter setting may influence thresholds in a complex acoustic environment like the sea.
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