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Effects of altered vessel traffic (and anthropogenic ocean noise) on the presence of harbour porpoises in the Belgian part of the North Sea
Debaveye, L. (2022). Effects of altered vessel traffic (and anthropogenic ocean noise) on the presence of harbour porpoises in the Belgian part of the North Sea. MSc Thesis. Universiteit Antwerpen/Ghent University/Vrije Universiteit Brussel: Antwerpen, Gent, Brussel. 38 pp.

Thesis info:

Trefwoorden
    Phocoena phocoena (Linnaeus, 1758) [WoRMS]
    Marien/Kust
Author keywords
    Harbour porpoise, Echolocation, Passive Acoustic Monitoring, C-pod, vessel route density, anthropogenic ocean noise, Covid-19 pandemic

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  • Debaveye, L.

Abstract
    Over the past decades, interest has been sparked in the marine research field concerning noise pollution in the world’s oceans. One of the main factors causing anthropogenic ocean noise is the presence of intense shipping activities. The produced noise coming from ships can travel and spread over long distances. This ‘ocean noise’, or sounds of anthropogenic sources can often interfere with or mask the natural ocean noises and therefore alter the ability of marine animals to navigate and communicate properly. In this research project, the subject of focus is the harbour porpoise (Phocoena phocoena) which is the most common toothed whale (Odontoceti) species present in the Belgian part of the North Sea (BPNS). The harbour porpoise utilises bio-sonar or echolocation (ultrasonic sound or ‘clicks’) to communicate with its peers, navigate in the marine environment and to find potential prey. To monitor the presence of the harbour porpoise, several C-pod sensor networks (falling under passive acoustic monitoring or PAM) were set up, as part of the VLIZ (Flanders Marine Institute) LifeWatch observatory and of the RBINS (Royal Institute of Natural Sciences) WinMon.BE project. Since several years this network registers porpoise activity and collects bio-sonar data at different stations in the Belgian part of the North Sea. In this thesis, research was done whether altered vessel route density (induced by the Covid-19 crisis) influenced the presence of the harbour porpoise presence in the BPNS. More specifically, we investigated (a) whether the Covid-19 crisis led to a change in vessel route density in the BPNS, (b) if this change in vessel route density had an influence on the presence of harbour porpoises. Our results showed that, even with many Covid-19 restrictions in place, the average vessel route density has intensified in 2020 (with a peak from June to August 2020). The main increase in overall vessel route density can be clarified by an increase in the vessel type ‘Other’ (containing research, maintenance and control vessels) in specific research zones. An explanation for this increase of ‘Other’ vessel route density can be linked to the construction of two Dutch offshore windfarm parks in the same period. The detections of harbour porpoises reach their peak in January – February and arrive at their lowest point during the months May to August. However, this is mainly linked to seasonality since similar findings, concerning seasonal porpoises distribution, come forward in literature (Haelters et al., 2013; Augustijns, 2018). Even though a significant relationship is found between the ‘Other’ vessel types and the presence of the harbour porpoises, only a weak negative correlation is present between the two variables. Further and different types of research will be needed in order to assess the true significance shipping traffic, and with it anthropogenic ocean noise, has on the presence of harbour porpoises in the BPNS.

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