MEP-NSW - Harbour porpoise acoustics
Assessment of the Effects of the Offshore Wind Farm Egmond aan Zee (OWEZ) for Harbour PorpoisePurpose:"The aim of this study was to investigate whether the Offshore Wind farm Egmond aan Zee(OWEZ) has influenced the occurrence of harbour porpoises.In order to evaluate the environmental impacts of OWEZ, porpoise acoustic activity in thearea was monitored;1) during a baseline (T0) study 2003/2004 (Brasseur at al. 2004)2) after the construction of the wind farm (T1) from 2007 to 2009.The comparison between the T0 and the T1 was conducted to determine if and how harbour porpoise occurrence is affected by the presence of the wind farm. Harbour porpoise activity and presence was measured by acoustic monitoring of echolocationsounds at eight stations equipped with stationary acoustic porpoise detectors (T-PODs) whichwere permanently deployed and were operating on a 24 hour basis. During both the T0 and T1study the T-PODs functioned very well and provided a wealth ofdata. Four indicators of click activity (porpoise positive minutes, clicks per porpoise positive minutes, encounter duration and waiting time between encounters) were chosen for the analyses. These indicators can be related directly to porpoise occurrence and habitat use in the study area. To investigate a potential effect of the wind farm a statistical Before-After Control-Impact (BACI) design was used. Here conditions in the wind farm (impact area, T1) were compared to both the baseline conditions (T0) and to conditions in the nearby reference area.The acoustic results show a strong seasonal variation in harbour porpoise occurrence, with more recordings of animals in the autumn/winter/spring seasons compared to the summer months. This pattern was similar in both the T0 and in the T1 study.There was a general increase in harbour porpoise occurrence from T0 to T1 for all T-POD stations, which was confirmed by an increase in porpoise sightings in the Dutch coastal area. During T0, the spatial distribution of porpoises did not differ significantly between the impact area (wind farm) and the two reference areas north and south of the wind farm.The results of the BACI design showed that during the T1 porpoises showed a significant change in distribution between the reference areas and the impact area. A higher porpoise acoustic activity was recorded inside the wind farm relative to outside, which is most likely linked to an increase in local porpoise occurrence. Because of the introduction of new T-PODs to the study and the specific differences between individual T-PODs , the variation between these devices might have caused a higher variation in the resulting data. Thus, when interpreting the effects, one should take into account that the confidence interval of the results might be larger and that the true effect might be stronger or lower than the one reported here. However, this does not influence the overall conclusions.The cause behind the increase of porpoises in the farm could not be determined, but may be linked to increased food availability due to the reef effect of the turbine foundations and the exclusion of fishery from the wind farm. The increase of harbour porpoise acoustic activity inside the wind farm is in contrast to results from other offshore wind farms. This shows that results from one wind farm are not necessarily transferable or valid for other wind farms located in different areas."
Simple
- Date ( Publication )
- 2012-02-02
- Status
- Completed
- Maintenance and update frequency
- As needed
- Keywords
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harbour porpoise
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acoustic
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wind farms
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MEP-NSW
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- Keywords ( Place )
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Noordzee
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- Access constraints
- Copyright
- Use constraints
- otherRestictions
- Spatial representation type
- Vector
- Metadata language
- en
- Character set
- UTF8
- Topic category
-
- Boundaries
- Begin date
- 2003-06-01
- End date
- 2009-05-01
- Supplemental Information
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- Reference system identifier
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EPSG
/WGS 84 (EPSG:4326)
/7.9
- OnLine resource
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Harbour Porpoise Acoustics - SubVersion repository for raw data and tools (INSPIRE download | OET raw)
(
WWW:LINK-1.0-http--link
)Raw data repository, accessible by http and svn.
- Hierarchy level
- Dataset
- File identifier
- 7799fc48-375d-44e2-be15-ebfef0606c0f XML
- Metadata language
- en
- Character set
- UTF8
- Parent identifier
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MEP-NSW - NearShoreWInd
22ed7799-aeab-46f7-a885-cc474274a274
- Date stamp
- 2014-12-18T14:55:48
- Metadata standard name
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ISO 19115:2003/19139
- Metadata standard version
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1.0
Deltares
-Gerrit Hendriksen / Willem Stolte
( )Boussinesqweg 1
,Delft
,2629 HV
,