Data and R codes.

<b>Aim:</b> Marine fish are increasingly threatened by global warming, yet the environmental driving factors for the fish biodiversity in the coast are unclear. Meanwhile, the lack of clarity regarding the responsive traits of coastal fish to environmental conditions has become a key barrier to deciphering the intricate biodiversity-environment relationships in coastal seas. This study aimed to disentangle the direct and indirect effects of environmental factors on fish communities in coastal China Seas, and identify the specific fish traits responsive to these environmental drivers.<b>Location: </b>China.<b>Methods: </b>Piecewise structural equation modeling was applied to determine the direct and indirect effects of environmental factors on fish communities in coastal China Seas, and fourth-corner combined with RLQ analysis was performed to identify fish responsive traits to environmental drivers.<b>Results: </b>The direct and indirect effects of temperature on fish species richness were contrary. The direct effect was negative (standardized coefficient: -0.29), which was associated with the adverse temporal impacts of global warming on biodiversity; the indirect effect was positive (value: 0.72), which explained the spatially higher biodiversity observed in warmer seas. Salinity, water depth, and seafloor substrate were confirmed as important drivers of fish communities, with effects linked to fish physiology (salinity), habitat availability (water depth, seafloor substrate), and feeding activities (seafloor substrate). Four key traits were identified as responsive to the environmental drivers: generation time, caudal peduncle throttling, pectoral fin size, and food consumption to biomass ratio. The Bohai Sea and Yellow Sea were associated with fish having longer generation time, smaller caudal peduncle throttling, smaller pectoral fin size, and lower food consumption to biomass ratio; the East China Sea showed intermediate trait characteristics; and the South China Sea exhibited trait patterns opposite to those of the Bohai Sea and Yellow Sea.