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Harbour porpoise activity in the German Bight remains stable

Long-term study shows: Harbour porpoise activity in the German Bight remains stable – varying detection rates in relation to offshore wind farms in operation

A study commissioned by the German Offshore Wind Energy Association (Bundesverbands Windenergie Offshore e.V.) and conducted by IBL Umweltplanung GmbH, in partnership with BioConsult SH, analysed 13 years of CPOD data from the German Bight. The findings reveal an overall stable trend in harbour porpoise detection rates, despite regional variations and possible shifts in habitat use. In addition, detection rates were on average 10% lower in the immediate vicinity of offshore wind farms compared to within the wind farms. The causes of this effect remain unclear and require further investigation.

On behalf of the Bundesverband Windenergie Offshore e.V., IBL Umweltplanung GmbH in cooperation with BioConsult SH GmbH & Co. KG, conducted a study based on over a decade of CPOD-monitoring data in the German Bight, consisting of two separate parts.

In the first part of the study, Bioconsult SH analysed long-term monitoring stations with regards to the development of porpoise detection rates throughout the years. It was found that, while being subject to annual fluctuations, overall detection rates within the German Bight were not significantly different from those ten years ago. Nevertheless, different trends were found for different subareas, pointing towards a shift distribution in the German Bight. The reasons behind the observed patterns are subject to discussion and still poorly understood.

In the second part of the study, IBL Umweltplanung GmbH, with professional statistical support from Moritz Mercker (Bionum GmbH), looked at differences between detection rates within operational windfarms and in their immediate vicinity (2.5 km buffer around windfarm area). Our results from the binary model show that overall harbour porpoise detection rates are significantly lower (by 10 %) in the immediate vicinity of windfarms than within. However, a clear gradient could not be determined. We thus very carefully conclude that compared to their immediate vicinity, windfarms rather have slight attraction than deterrence effects on harbour porpoises. The reasons for the observed patterns are still subject to further research.

Click here to download the study (in English) 

 

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