AUTHOR=Gim Jeong-Soo , Hong Donghyun , Joo Gea-Jae , Kim Dong-Kyun , Lee Ji-Young , Kwak Seok-Nam , Jeong Kwang-Seuk , Jeppesen Erik , Jo Hyunbin 

TITLE=Responses of fish population structure to barrage re-opening in an estuarine ecosystem

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 12 - 2025

YEAR=2025

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1542823

DOI=10.3389/fmars.2025.1542823

ISSN=2296-7745

ABSTRACT=BackgroundRe-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.MethodsWe 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).ResultsDuring 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.DiscussionOur 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.