Fish Aggregation Around a Coastal Wind Farm: Stereo-BRUV and Complementary Surveys

The rapid expansion of offshore wind energy in Korea has raised concerns among coastal fishing communities about potential changes in fish assemblages. We conducted a summer 2022 survey at the Tamra Offshore Wind Farm (Jeju, Korea), comparing turbine-adjacent and reference sites using diver-operated video (DOV), direct capture, and stereo-baited remote underwater video (stereo-BRUV). Across methods, 23 fish species were identified, and stereo-BRUV detected the highest species richness. In stereo-BRUV analysis, the observed fish species and relative abundance metrics were higher in turbine-adjacent sites than reference site, including greater MaxN (maximum number of individuals observed in a single video frame) and Max spp. (maximum number of species observed in a single video frame). Most individuals measured from stereo imagery were 15–25 cm in total length (TL). For dominant taxa, TL distributions derived from stereo-BRUV were comparable to those measured from captured specimens, supporting the practical use of stereo-BRUV for size–structure characterization. Epifaunal assemblages on turbine jackets exhibited higher density and biomass than the reference site and showed clear vertical stratification (upper/mid > bottom). Diet items in captured fish overlapped with dominant jacket epifauna, consistent with a potential trophic linkage. Overall, stereo-BRUV can be used as a non-destructive and auditable approach for documenting fish assemblages around wind-farm structures. Because sampling was limited in spatial and temporal replication, the observed patterns should be interpreted as exploratory and hypothesis-generating for future synchronized and replicated monitoring.