The rapid expansion of offshore wind farms challenges the reliability of ICES-coordinated fish surveys—insights from the Baltic Sea

Abstract

Fish stock assessment and sustainable management requires that the whole distribution area of the managed fish stocks is representatively sampled. Along with an increasing demand for renewable energy in Europe, a growing number of areas are allocated for current and future offshore wind farms (OWF). Besides various unknown environmental effects, impacts on different stakeholder activities, such as fisheries, are considered during the implementation process. Scientific interests and tasks are, however, often marginalized. The current ban of commercial fisheries and fisheries monitoring in OWFs, in combination with an increase of OWF areas and habitat alteration within OWFs, might therefore bias the time series of scientific surveys and, thus, fisheries stock assessments. The expected increase in the overlap between OWFs and scientific fish surveys coordinated by the International Council for the Exploration of the Sea (ICES) in the Baltic Sea could result in, depending on the survey, up to 6.6–11.5% of the stations and transects being unavailable for sampling. We discuss the potential consequences for survey time series and stock assessments. Further, we aim to stimulate the discussion about the future of current standard surveys in the context of rapid expansions of OWFs, including the need for adaptations in survey design.

Identifying fit-for purpose methods for monitoring fish communities

“…The Baltic sea is a semi-enclosed, low-diversity brackish sea with a long history of anthropogenic use and currently suffers from multiple stressors like eutrophication, deoxygenation, acidification, warming and overfishing (Reusch et al, 2018). There is an increasing demand of Offshore Windfarms with a planned increase in the long term from 31 OWFs with a spatial expansion of around 500 km² to 149 OWFs with an approximate 5-fold expansion (Haase et al, 2023). Currently fishing for commercial use and fisheries research is prohibited (Haase et al, 2023) within OWFs.…”

“…There is an increasing demand of Offshore Windfarms with a planned increase in the long term from 31 OWFs with a spatial expansion of around 500 km² to 149 OWFs with an approximate 5-fold expansion (Haase et al, 2023). Currently fishing for commercial use and fisheries research is prohibited (Haase et al, 2023) within OWFs. Besides the drastic expansion of OWFs in the Baltic Sea, marine protected areas (MPAs) will likely be expanded so that 30% of the EEZ are under protection and 10% of those under special protection by 2030 (EU, 2021).…”

“…Since it is not finally clarified whether traditional monitoring methods like bottom trawling are still viable in MPAs and are no longer an option in OWFs, the areas where traditional mobile bottom contacting methods have been used decrease while the area of "black boxes" in fisheries science increase. For example, some sampling stations of the ICES coordinated Baltic International Trawl Survey (BITS), which aims to provide data on demersal commercial species, in fact collide with OWFs in the Baltic Sea (Haase et al, 2023) (Figure 2) and become "black boxes" for fisheries management. Therefore, adaptive methods to collect data are required to be able to i) detect changes in fish communities occurring in these areas and ii) provide information for fisheries management (ICES, 2023) if necessary.…”

“…in OWF). These potential `no fishing areas' may become a blind spot for fisheries research if no other alternative monitoring method is available to collect necessary information (Haase et al, 2023). On the other hand, MPAs are conservation measures and may help in sustaining fisheries (Kriegl et al, 2021) and hence their efficacy needs to be monitored and understood, as well as the impacts of OWFs on the marine ecosystem and associated fish communities that are not yet fully understood (Lindeboom et al, 2011;Abramic et al, 2022).…”