No need to shout? Harbor porpoises (<i>Phocoena phocoena</i>) echolocate quietly in confined murky waters of the Wadden Sea

Dähne, Michael; Bär, Tom; Gallus, Anja; Benke, Harald; Herold, Elisabeth; Stilz, Peter

doi:10.1121/10.0002347

Cited by 3 publications

(3 citation statements)

References 26 publications

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“…Future studies should devote a bigger proportion of the overall effort to collecting detectability data from animal encounters, which will likely necessitate using lower cost detectability measurement methods than the tracking experiment. A suitable method would be multiple deployments of vertical hydrophone arrays with four or more channels, allowing distances to be calculated up to approximately 70–100 m (Dähne et al, 2020; Kyhn et al, 2013). However, to gather sufficient click data in the Baltic Proper, these systems would have to work autonomously over long time frames (at least weeks to months).…”

Section: Discussionmentioning

confidence: 99%

“…A challenge in using passive acoustics to detect harbour porpoises is that their echolocation signals are highly directional (Au et al, 1999; Koblitz et al, 2012; Macaulay et al, 2020), and they may adapt their source levels to different acoustic habitats (Dähne et al, 2020). Although the directionality is partly compensated by the scanning movements of the head performed by harbour porpoises (Verfuss et al, 2009), the combined effect of click directionality, source level, head‐scanning behavior, and general swim direction on the detectability of harbor porpoises needs to be measured empirically.…”

Section: Methodsmentioning

confidence: 99%

Section: Tracking Experimentsmentioning

confidence: 99%

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

Amundin¹,

Carlström

Thomas

et al. 2022

Ecology and Evolution

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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

Amundin¹,

Carlström

Thomas

et al. 2022

Ecology and Evolution

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Harbour porpoise (Phocoena phocoena) in the Wadden Sea World Heritage Site and requirements for trilateral monitoring

Scheidat,

Vrooman,

Teilmann

et al. 2024

Mar. Biodivers.

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The harbour porpoise (Phocoena phocoena) is considered part of the ‘Outstanding Universal Value’ characterising the Wadden Sea World Heritage Site (WS WHS). The Trilateral Wadden Sea Plan aims to preserve the conservation status of the Trilateral Wadden Sea Cooperation Area, encompassing the WS WHS. The plan has specified two conservation targets for the harbour porpoise: (1) viable stocks and a natural reproduction capacity and (2) conservation of habitat quality for its conservation. To assess the current occurrence of the harbour porpoise in the Wadden Sea area, we collated and analysed data from regional and national research projects using telemetry, aerial surveys, strandings and passive acoustic monitoring, obtained over the years 1990–2020. The results illustrate that porpoises occur in both offshore and intertidal waters, showing seasonal movements and changes in local occurrence over time. Some porpoises displayed limited home ranges throughout the year, suggesting a possible residency for some of the animals using the Wadden Sea area. We also showed that methods, frequency and spatial coverage of monitoring activities vary among the countries Denmark, Germany and the Netherlands. We discuss the suitability of the different methods both regarding the challenges of monitoring in the complex Wadden Sea habitat as well as their ability to target the conservation aims of the WHS. We give several recommendations to assess the status of the species to meet the identified conservation aims.

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Echolocation clicks of free-ranging Indo-Pacific finless porpoises (Neophocaena phocaenoides) in Hainan waters

Zhao

Giorli

Caruso

et al. 2023

The Journal of the Acoustical Society of America

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The echolocation clicks of free-ranging Indo-Pacific finless porpoises (IPFPs, Neophocaena phocaenoides) have been rarely studied in the wild. This paper aims at describing the echolocation-click characteristics of IPFPs and examining whether IPFPs adapt their sonar system to the habitats in Hainan waters, China. The echolocation clicks were recorded using a 13 elements star-shaped array of hydrophones. A total of 65 on-axis clicks were identified and analyzed. IPFPs use echolocation clicks with a source level (SL) of 158 ± 9 dB re: 1 μPa peak-peak, mean peak, and centroid frequency of 134 ± 3 kHz, −3 dB bandwidth of 14 ± 2 kHz and produce at inter-click intervals of 104 ± 51 ms. The results relative to other porpoises show that finless porpoises in Hainan waters produce clicks with moderate SLs and high peak frequency. These results could be useful in detecting the presence and estimating the density of IPFPs during passive acoustic monitoring in the study area and serve to shed light on the interpopulation variation of click characteristics of finless porpoises as well.

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No need to shout? Harbor porpoises (Phocoena phocoena) echolocate quietly in confined murky waters of the Wadden Sea

Cited by 3 publications

References 26 publications

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

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

Harbour porpoise (Phocoena phocoena) in the Wadden Sea World Heritage Site and requirements for trilateral monitoring

Echolocation clicks of free-ranging Indo-Pacific finless porpoises (Neophocaena phocaenoides) in Hainan waters

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