Changes in Fish Assemblages after Dike Construction in the Saemangeum Area

Abstract

In the Saemangeum area, construction of a dike began in 1991 and was completed in 2006; desalination is currently being conducted. In order to investigate the influence of dike construction on fish assemblages, we analyzed the changes in fish assemblages using fish monitoring data accumulated before, during, and after construction of the Saemangeum Dike. Analysis of changes in the salinity of the Saemangeum Reservoir between 1997 and 2014 revealed that the overall salinity decreased, and this pattern became evident after completion of the dike. Long-term changes in fish assemblages were also confirmed in freshwater areas (Mankyeong and Dongjin Rivers) and the Saemangeum Reservoir. In freshwater areas, different fish assemblages were collected before and after dike construction according to NMDS analysis, and the proportion of freshwater fish continuously increased during analysis of ecological types. In the Saemangeum Reservoir, differences in fish assemblages were observed before, during, and after dike construction (PERMANOVA, F = 2.5325, P = 0.017). Moreover, the numbers of families and species decreased during dike construction; in terms of species composition, the proportion of brackish water fish increased, while that of marine fish decreased. Currently, a salinity gradient exists in the Saemangeum area between the rivers and the dike, and the M1-3 and D1-3 sites were classified as freshwater sites. Desalination is expected to increase freshwater areas in the future; as the change will happen over a very long period of time, differentiated management plans for each site of the Saemangeum area should be implemented through continuous monitoring.