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

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; 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 66-1,143 individuals (95% CI, point estimate 490) 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 neighbouring 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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Geographical and seasonal variation of harbour porpoise (Phocoena phocoena) presence in the German Baltic Sea revealed by passive acoustic monitoring

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315407054938 ◽

2007 ◽

Vol 87 (1) ◽

pp. 165-176 ◽

Cited By ~ 62

Author(s):

Ursula K. Verfuß ◽

Christopher G. Honnef ◽

Anja Meding ◽

Michael Dähne ◽

Roger Mundry ◽

...

Keyword(s):

Seasonal Variation ◽

Baltic Sea ◽

Research Effort ◽

Natura 2000 ◽

Acoustic Monitoring ◽

Harbour Porpoise ◽

Passive Acoustic Monitoring ◽

Cetacean Species ◽

Passive Acoustic ◽

The Impact

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. A correlation of the results with the longitude of the measuring position revealed a significant decrease from west to east in the percentage of days with porpoise detections. Comparison of data gathered in the first quarters with the third quarters of the monitoring years displayed a seasonal variation with fewer days of porpoise detections in winter time than in summer time. Nevertheless, harbour porpoises have been detected year-round at most of the measuring positions in the German Baltic Sea. The present study clearly indicates a regular use of the German Baltic Sea by harbour porpoises with a geographical and seasonal variation in the usage of the German Baltic Sea. The larger numbers of harbour porpoise detections in spring to autumn compared with winter suggests that the German Baltic Sea is an important breeding and mating area for these animals.

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Use of static passive acoustic monitoring to assess the status of the ‘Critically Endangered’ Baltic harbour porpoise in German waters

Endangered Species Research ◽

10.3354/esr00448 ◽

2012 ◽

Vol 18 (3) ◽

pp. 265-278 ◽

Cited By ~ 25

Author(s):

A Gallus ◽

M Dähne ◽

UK Verfuß ◽

S Bräger ◽

S Adler ◽

...

Keyword(s):

Acoustic Monitoring ◽

Harbour Porpoise ◽

Critically Endangered ◽

Passive Acoustic Monitoring ◽

The Status ◽

German Waters ◽

Passive Acoustic

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Passive Acoustic Monitoring Reveals Spatio-Temporal Distributions of Antarctic and Pygmy Blue Whales Around Central New Zealand

Frontiers in Marine Science ◽

10.3389/fmars.2020.575257 ◽

2021 ◽

Vol 7 ◽

Author(s):

Victoria E. Warren ◽

Ana Širović ◽

Craig McPherson ◽

Kimberly T. Goetz ◽

Craig A. Radford ◽

...

Keyword(s):

New Zealand ◽

Acoustic Monitoring ◽

Critically Endangered ◽

Blue Whale ◽

Passive Acoustic Monitoring ◽

Animal Populations ◽

Spatio Temporal ◽

Species Specific ◽

Passive Acoustic ◽

Blue Whales

Effective management of wild animal populations relies on an understanding of their spatio-temporal distributions. Passive acoustic monitoring (PAM) is a non-invasive method to investigate the distribution of free-ranging species that reliably produce sound. Critically endangered Antarctic blue whales (Balaenoptera musculus intermedia) (ABWs) co-occur with pygmy blue whales (B. m. brevicauda) (PBWs) around New Zealand. Nationally, both are listed as “data deficient” due to difficulties in access and visual sub-species identification. PAM was used to investigate the distributions of blue whales via sub-species specific song detections in central New Zealand. Propagation models, incorporating ambient noise data, enabled the comparison of detections among recording locations in different marine environments. ABW detections peaked during austral winter and spring, indicating that New Zealand, and the South Taranaki Bight (STB) in particular, is a migratory corridor for ABWs. Some ABW calls were also detected during the breeding season (September and October). PBW calls were highly concentrated in the STB, particularly between March and May, suggesting that an aggregation of PBWs may occur here. Therefore, the STB is of great importance for both sub-species of blue whale. PBW detections were absent from the STB during parts of austral spring, but PBWs were detected at east coast locations during this time. Detection area models were valuable when interpreting and comparing detections among recording locations. The results provide sub-species specific information required for management of critically endangered ABWs and highlight the relative importance of central New Zealand for both sub-species of blue whale.

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Geographical variation in harbour porpoise (Phocoena phocoena) skulls: Support for a separate non-migratory population in the Baltic proper

Ophelia ◽

10.1080/00785236.2002.10409484 ◽

2002 ◽

Vol 56 (1) ◽

pp. 1-12 ◽

Cited By ~ 21

Author(s):

S. Huggenberger ◽

H. Benke ◽

C. C. Kinze

Keyword(s):

Geographical Variation ◽

Harbour Porpoise ◽

Phocoena Phocoena ◽

Baltic Proper ◽

Migratory Population ◽

The Baltic

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Presence and behavior of harbor porpoises (Phocoena phocoena) around set nets revealed using passive acoustic monitoring

Fisheries Research ◽

10.1016/j.fishres.2018.03.003 ◽

2018 ◽

Vol 204 ◽

pp. 269-274 ◽

Cited By ~ 1

Author(s):

Hiroki Higashisaka ◽

Takashi Matsuishi ◽

Tomonari Akamatsu

Keyword(s):

Acoustic Monitoring ◽

Phocoena Phocoena ◽

Passive Acoustic Monitoring ◽

Passive Acoustic ◽

And Behavior ◽

Harbor Porpoises

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Presentation of Binning-Based Inter-Click Interval Data from Passive Acoustic Monitoring of Free-Ranging Harbour Porpoises (Phocoena Phocoena)

10.20855/ijav.2020.25.21583 ◽

2020 ◽

Vol 25 (2) ◽

pp. 209-218

Author(s):

Maximilian Ruffert ◽

Victoria L.G. Todd ◽

Ian B. Todd

Keyword(s):

Interval Data ◽

Acoustic Monitoring ◽

Phocoena Phocoena ◽

Passive Acoustic Monitoring ◽

Equal Rate ◽

Click Train ◽

Judicious Choice ◽

Binned Data ◽

Passive Acoustic ◽

Free Ranging

C-PODs are used for Passive Acoustic Monitoring (PAM) of harbour porpoises (Phocoena phocoena) at an offshore open sea location in the German North Sea. Diel patterns of echolocation click trains are extracted from minimum inter-click interval (minICI) data by binning. The aim of this study is to reassess and refine minICI ranges of click train data with particular consideration to the binning widths. Emphasis is also placed on choosing an appropriate visualisation of these binned data. Key ecological results include presence of higher train rates during the day with intermediate minICI values defined by the range 6-28 ms and a higher train rate with short minICI values 1.25-2.00 ms at night. This indicates an increase in porpoise feeding behaviour, or change of style, at night. Click trains with long minICI values > 35 ms occur at an equal rate throughout both diel phases, suggesting a more routine behaviour, such as navigation. Results could be revealed only by judicious choice of binning widths, e.g. previously overlooked patterns within historical echolocation data. The classification methodology can be used to analyse echolocation trains from a variety of species and can be applied to any PAM data with the relevant click parameters.

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