Effects of operational off-shore wind farms on fishes and fisheries. Review report

Offshore wind farms (OWFs) are a crucial element for achieving a sustainable future due to their provision of renewable energy. The rapid expansion and build-out scenarios of OWFs often surpasses the knowledge of their long-term impacts on biodiversity, specifically on fish communities. Therefore, acceptance of OWFs may vary between areas, and the fishing industry is often concerned, although some cases have revealed the potential for collaboration between OWFs and commercial fisheries.

Worldwide, researchers are producing relevant information, ranging from OWF effects on different marine species and ecosystems to management strategies for dealing with conflicts in overlapping areas of OWFs and fisheries. However, the knowledge remains scattered in the scientific literature and may advance at a higher pace than the rate at which the observations are clustering.

Aiming to provide an informed understanding of the potential influence of OWFs on fish and fisheries, we conducted a systematic review of peer-reviewed scientific literature. Specifically, we assessed the direct effects of four potential stressors: electromagnetic fields (EMFs), underwater noise (UWN), particle motion (PM), and vibration, relevant for OWFs during the operational stage.

We targeted the operational stage, because it is the longest stage of an OWF, covering most of its lifetime. Moreover, to date, environmental research on the potential impacts during the OWF construction stage surpasses previous environmental research relevant for the operational stage. Using results from Web of Science and Scopus search engines, we covered a total of 5,181 records and applied scientific review approaches to identify 67 scientific publications of direct relevance to the review topics.

We observed that most literature consisted of non-empirical studies (i.e., not producing new data; n=40), while empirical studies (i.e., producing new data; n=27) were scarce and mainly restricted to EMFs (n=17) and UWN (n=10). Our results show a positive trend in the number of peer-reviewed studies published per year, likely associated with increasing concern about anthropogenic impacts related to global OWF developments.

Subsea cables used for inter-array and offshore-onshore transportation of energy emit anthropogenic EMFs into the surrounding environment that may be perceived by a range of electro- and magnetoreceptive fishes. While such emissions have the potential to alter the movement and migratory behaviour of fishes, our review indicates that current evidence of negative EMF effects are mainly limited to laboratory studies assessing early life development of fish.

These laboratory studies generally indicate significant alterations in a variety of developmental processes, yet EMF intensities and exposure times are variable and often exceed values encountered near OWFs, making it challenging to extrapolate laboratory findings and assess wider population-level impacts for fish and fisheries.

In addition, laboratory experiments may be associated with methodological artifacts. For example, when restricting the spatial positioning of the study organism within close proximity of the EMF source, the study results may not reflect realistic in situ exposure times and intensities. Although behavioural and physiological changes have been reported in fish exposed to UWN levels associated with operational OWF, the changes appear to be limited.

Direct experiments covering the effects of OWF induced PM or vibration on fish were not found in the examined literature, however, PM and vibration were consistently highlighted as relevant but largely overlooked stressors. In addition, OWF structures may have several ecosystem effects in marine environments, including stepping-stone effects for indigenous and non-indigenous species and local artificial reef effects.

Specifically, OWF structures may enable indigenous and non-indigenous species to occur in novel areas, while OWF scour protection and foundations may benefit species associated with hard substrates, providing shelter, food, and reproduction opportunities, similar to artificial reefs. As the OWF industry is rapidly expanding to meet the increasing demand for renewable energy, we also briefly explore floating OWF technologies that are currently emerging and discuss their potential effects on fish.

In addition, we briefly outline management strategies that can be employed to minimize the risk of negative impacts on fish and fisheries due to future OWF expansion. Finally, we summarize important future research areas that were identified by this review as critical to advance our limited understanding of OWF impacts on fish and fisheries.

In general, we recommend allocating resources for experimental in situ research accounting for fish exposure to known levels of relevant stressors (e.g., EMF, UWN, PM, vibration) and assessments of physiological and behavioural responses in fish.