Frontiers in Marine Science, cilt.12, 2025 (SCI-Expanded, Scopus)
Background: Re-openings of estuary barrages for ecosystem restoration are rare globally. The Nakdong River Estuary (NRE), South Korea, provides a unique opportunity to assess the effects of temporary barrage re-opening on fish population structure. Methods: We conducted monthly fish population surveys both upstream and downstream of the estuary barrage from 2021 to 2023, categorizing results into closing period (CP) and opening period (OP). Results: During the OP, we observed shifts in fish distribution, including decreased proportions of non-indigenous species and altered habitat distributions. Additionally, we observed an increase in brackish water species populations and their upstream movement. Monthly frequency analysis revealed that brackish and non-indigenous species exhibited high frequencies mainly during OP (July to October), while freshwater (demersal) species showed low frequencies during the same period. Discussion: Our study highlights the significant impact of temporary estuarine ecosystem restoration on fish distribution and emphasizes the need for careful consideration of both frequency and duration of estuary barrage re-openings.