Effect of pile driving on the seasonal and geographical distribution of the harbourporpoise (Phocoena phocoena) in the Belgian part of the North Sea
De Pauw, L. (2022). Effect of pile driving on the seasonal and geographical distribution of the harbourporpoise (Phocoena phocoena) in the Belgian part of the North Sea. MA Thesis. Universiteit Gent, Faculteit Bio-ingenieurswetenschappen: Gent. 62 pp.
This study analyses the effects of pile-driving on porpoises in the Belgian part of the North Sea (BPNS). This study will be divided into four parts: a literature review, description of the methodology, data exploration and a modelling part where final conclusions can be drawn. Harbour porpoises are among the most sensitive marine mammals in the BPNS and play an important role in the multi-trophic ecosystem of the BPNS. They are described as a protected species by the Habitats Directive. Offshore wind farms arean emerging, sustainable technology that provides green energy. However, there are indications in the literature suggesting that the construction of these wind farms has a negative impact on porpoises. Specifically, the driving of the foundation piles into the ground, called ”pile driving”, could negatively affect porpoises. In order to collect data on porpoise activity, a passive acoustic monitoring network has been set up in the BPNS. This network uses a series of continuous porpoise detectors (C-PODs) deployed at fixed locations to detect porpoise activity. Data fromJuly 1, 2018 to June 30, 2020 were combined with pile-driving information to evaluate its impact on porpoise presence. After cleaning up and merging the datasets, we first looked for general patterns in the presence of harbor porpoises in the BDNZ and their presence patterns related to piling. The examination of the C-POD data showed that porpoises were more present in winter than summer and appeared to be more active at night than during the day. Pile-driving events occurred only in summer, fall, and winter and appeared to be correlated with temporary porpoise presence. Generalized Additive Models (GAM) were used to determine if the probability ofdetecting a harbor porpoise changed before, during, and immediately after the piling event. This probability was found to be reduced in the vicinity of the works, during and up to 120 hours after the works were carried out. In general, it can be concluded that the presence of porpoises is affected by pile driving and that this is also likely to affect the abundance of porpoises in the BPNS.
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