There’s no plaice like an offshore wind farm

Offshore wind farms are built at a high rate in European waters to make the transition towards more green energy sources. Their development takes up marine space that is often not available anymore to other users such as the fisheries sector. This while knowledge on the ecological effects of wind farms on commercial flatfish was lacking. Understanding the effects of an offshore wind farm on a fish species requires knowledge on its movements within and its association to the wind farm area. Therefore, a tagging study making use of an acoustic receiver network was carried out in the Belwind wind farm (Belgium). This study aimed at detecting the presence of plaice Pleuronectes platessa, an important commercial flatfish species, and to study its small-scale movements around the turbine foundations.

"The tripod setup from the Lifewatch acoustic receiver network allowed us to investigate the movement behaviour of plaice within the wind farm. Without these tripods, we wouldn't have been able to investigate the fish positions in so much detail so close to the turbines."

Jolien Buyse

As a PhD student at the Flanders Research Institute for Agriculture, Fisheries and Food (ILVO) and Ghent University, Jolien studied the ecological impacts of offshore wind farms on flatfish, using plaice as a focus species. The knowledge obtained in this PhD can be further used to inform management decisions on marine spatial planning and future wind farm developments.

Objectives

Due to the increased presence of offshore wind farms in European waters, it is crucial to have a good understanding of their impacts on the marine environment. Therefore, a tagging study was performed within the context of a PhD study that aimed at investigating the ecological effects of offshore wind farms on plaice. Acoustic telemetry was chosen as a method to study their residency, site fidelity and small-scale movements around the hard substrates in order to gain insight into their behaviour within an offshore wind farm. The residency of a fish, calculated from the presences of the fish over a certain period, represents its level of association to the study area. A high residency would thereby indicate that the fish rarely leaves the wind farm, which increases the protective capacity of the area. Further, we were interested whether the fish returned to the wind farm area after their spawning migrations during the winter months (i.e. site fidelity). We therefore studied their presence within the wind farm area over the period of an entire year. Lastly, to determine whether and when plaice preferred the hard substrate or the soft sediment, fish positions around certain turbines were calculated based on the detections. Patterns in distances to the hard substrate in relation to the time of day were analysed to detect habitat preferences that were potentially linked to feeding behaviour.

Methodology

A temporal network of acoustic receivers was deployed over a period of one year within the Belwind wind farm in collaboration with the Flanders Marine Institute (VLIZ) and Wageningen Marine Research (WMR). The receivers were deployed onto the seabed using a steel tripod system that could be retrieved using an acoustic release system for easier maintenance (see Goossens et al. (2020) for a full description of the mooring method). In addition, the permanent acoustic receiver network of the Belgian Lifewatch Observatory was used to track fish when they moved outside of the wind farm area.

Plaice individuals were caught by divers or using hook-and-line fishery within the Belwind wind farm. We opted for an external attachment of the transmitters to the fish, as the small body cavity of flatfish makes surgical implantation less suitable. If a plaice equipped with a transmitter swam in the vicinity of a receiver, the unique ID-code of the transmitter was stored on the receiver together with a time stamp. As such, we could establish if fish were present within the wind farm area and whether a fish remained there for a prolonged period of time. Further, we also deployed multiple receivers very close to particular turbines to study the small-scale movements of plaice around the hard substrates. If the transmitter signal is picked up by at least three receivers, the position of the fish can be calculated using triangulation. Such position information can tell us something about the habitat preferences of the fish related to the presence of the wind turbines.

Used components of the LifeWatch Infrastructure

Sensor network

Apart from the temporal network of receivers that was deployed in the Belwind wind farm, the permanent fish acoustic receiver network of the Belgian LifeWatch Observatory was also used to detect plaice presence in the Belgian part of the North Sea.

Data management

The data of both temporary and permanent acoustic receiver networks are stored in the European Tracking Network (ETN) data portal. This data portal was developed in the framework of LifeWatch and allows the access and sharing of aquatic telemetry data. The data analysis was performed using the LifeWatch RStudio server, which offers high computing power and immediate access to the ETN portal.

Output

Publications

Buyse, J., 2023. Ecological impacts of offshore wind farms on flatfish with emphasis on plaice pleuronectes platessa, a species of commercial interest in the southern north sea. Ghent university.

Goossens, j., Buyse, J., et al., 2022. Taking the time for range testing : an approach to account for temporal resolution in acoustic telemetry detection range assessments. Anim. Biotelemetry 1–13. https://doi.org/10.1186/s40317-022-00290-2

Scripts

Scripts will be made available on the GitHub page of Jolien, once the final results are published.

News and Outreach

2023-02-28, Testerep magazine - Pladijs profiteert van windmolenparken op zee

2023-03-02, VRT nieuws - Meer krabben, kreeften en vissen in windmolenparken aan de kust: "Ze voeden zich met mosselen uit holtes van windmolens"

2023-03-02, De Morgen/Het Nieuwsblad/Metro - Pladijs profiteert van windmolenparken op Noordzee

Movie about the PhD research showing underwater footage

Contact

E-mail: jolien.buyse@ilvo.vlaanderen.be
Tel.: +32 59 56 98 36 / +32 479 90 77 74

Find Jolien Buyse on ResearchGate.

Useful links

Fish acoustic receiver network: Learn about the fish telemetry network of the Belgian LifeWatch Observatory.
ETN: Access, store and share fish tracking data on the European Tracking Network data platform.
Data explorer: Access and explore the acoustic fish detection data with the LifeWatch data explorer.

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