To clarify the sedimentation characteristics of aquaculture-derived organic matter (AOM) from a large yellow croaker () cage farm in Sansha Bay, AOM samples in a sampling gradient (0-200 m away from the culture cage) were collected with sedimentation traps under two typical feeding conditions (commercial feed and raw fish). These samples were used to analyze sedimentation rate, particle organic matter (POM:particulate organic matter; POC:particulate organic carbon; PN:particulate nitrogen; TP:total phosphorus) fluxes, and their spatial expansion in this study. The sedimentation rate of AOM was (563.66±119.18) g/(m²·d) when commercial pellets were used as feed, which was significantly higher than that when raw fish was used. Particulate organic matter (POM), POC, PN, and TP fluxes were much higher when using commercial feed than raw fish, at (27.25±2.43) g/(m²·d), (6.03±0.58) g/(m²·d), (0.66±0.06) g/(m²·d), and (0.39±0.04) g/(m²·d) in the former experimental condition, and at (13.04±1.62) g/(m²·d), (3.57±0.45) g/(m²·d), (0.51±0.06) g/(m²·d), and (0.22± 0.04) g/(m²·d) in the latter situation, respectively. Particle organic matter fluxes and AOM sedimentation rates showed decreasing tendencies from 0-100 m away from the fish cage, with a particularly strong decline in the raw fish treatment. The percentage of particle organic matter in AOM also exhibited spatial variability, declining in the region from the fish cages to 50 m downstream. In summary, the environmental effects of a cage farm in Sansha Bay were much remarked when commercial pellets were used as feed. Environmental impacts derived from using both commercial pellets and raw fish were restricted to an area 50-100 m away from fish cages. The occurrence of conspicuous environmental impacts due to using commercial feeds was associated with a greater AOM sedimentation rate, and thus, studies on restricted feeding and on the efficiency of fish feed are essential to alleviate the negative impacts of aquaculture in the area.