Retrospective analyses of offshore wind farm impacts on fisheries and benthic habitat interactions

The expansion of offshore wind farms (OWFs), driven by increasing global energy demands and marine spatial planning, is intensifying spatial conflicts and impacting fisheries. However, research on observed local and cumulative effects of OWFs on fisheries, especially regarding fishing effort reallocation, is limited. Retrospective analyses are crucial for informing science and policy. Denmark, a pioneer in large-scale OWFs, has over 15 operational farms totaling more than 2500 MW, with some early installations already decommissioned after 25 years. Analyses of the impacts and interactions between OWFs and various fishing fleets were conducted for four major Danish OWFs in the North Sea, Kattegat, and Western Baltic Sea from 2005 to 2023. This timeframe covers pre-, during-, and post-construction phases of the OWFs. Using available vessel monitoring system (VMS) and logbook data, we analyzed vessel-level fishing effort allocation, fishing efficiency, revenues and landings in relation to OWFs, fishing method, and benthic habitat fishing grounds, providing valuable insights into OWF-fisheries dynamics. This study identified major impacts of OWFs on Danish fisheries, as active fisheries within OWF sites generally ceased following construction. However, results indicate potential for reallocating fishing activities to surrounding areas offering similar opportunities. Most vessels are not exclusively dependent on OWF areas, as they typically have flexibility to switch between fisheries or gears and operate across wider areas due to their long range and polyvalent capabilities. Although minor gear-specific variations and localized concentrations in fishing effort were observed just outside OWF boundaries after their establishment, overall fishing patterns and efficiencies remained significantly consistent after OWF establishment – except for one OWF area. Fishing activity within and adjacent to OWFs showed in general similar gear composition, effort allocation, benthic habitat preferences, depth distributions, landings and economic efficiency, and species composition. Spatial fishing patterns associated with habitat also persisted and there was in general found continuity in fishing dynamics in surrounding areas following OWF establishment.