Long-term changes of the community structure of demersal fish species in the East China Sea and Yellow Sea

Abstract This study provides the first comprehensive long-term analysis of demersal fish community structure in the East China and Yellow seas using Japanese bottom trawl fishery data spanning four decades (1982–2023). Using nonparametric multidimensional scaling, we identified five distinct fish assemblages with spatial segregation patterns that changed significantly over time.Fish communities showed progressive spatial shifts, with clusters dominated by economically valuable species such as flatfishes and Japanese common squid in the Yellow Sea, and large Sciaenidae and conger pike along coastal China, undergoing substantial range contractions during the 1980s–1990s due to intensive fishing pressure. Sequential changes in target species were observed as fishing pressure transitioned from high-value species to alternatives including largehead hairtail, cuttlefish, and swordtip squid following initial species declines. Japanese fishing grounds reduced to waters near Japan after the mid-1990s due to international fishery agreements, coinciding with community structure changes. Current Japanese operations target yellow and red seabreams with stable catches under reduced fishing effort. This analysis demonstrates that fishing pressure and fleet redistribution due to international agreements considerably influenced demersal fish community dynamics. Future research requires multinational collaboration integrating data from China, the Republic of Korea, and Japan for comprehensive regional assessment of transboundary marine ecosystem changes.