The Chinese tapertail anchovy (Coilia nasus) is a typical anadromous fish species. Its spawning grounds are located in numerous river-connected lakes throughout the middle and lower reaches of the Yangtze River. Since the mid-20th century, the construction of embankments and sluice gates has disconnected most of these lakes from the main channel of the Yangtze River, preventing C. nasus from spawning and rearing offspring. In the Chaohu Lake, the primary river-connected channel has been equipped with sluice gates, resulting in the lake disconnected from the Yangtze River, and the population of C. nasus in Chaohu Lake being classified as landlocked. Although fish passages and boat sluice gates may still offer opportunities for migratory fish, no studies have yet investigated whether migratory C. nasus still exists in the lake. Investigating the ecological types of C. nasus in Chaohu Lake and tracing their origins can enhance our understanding of its migratory ecology and provide a more comprehensive view of lake connectivity, improving our ability to protect the ecology of Chaohu Lake. In July 2022, nine adult C. nasus samples were collected from Chaohu Lake in the Anhui Province, China. In this study, the otolith Sr/Ca ratio was analyzed using an Electron Probe Microanalyzer (EPMA) to determine the habitat history of C. nasus collected from Chaohu Lake. The ⁸⁷Sr/⁸⁶Sr ratio of otoliths was analyzed using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to trace the origin of some C. nasus individuals. The results showed that seven out of nine C. nasus individuals collected from Chaohu Lake exhibited low otolith Sr/Ca ratio profiles from the core to the edge. Change-point analysis revealed that the average values at different stages of these otoliths were all below three, indicating a freshwater life history. Moreover, the Sr/Ca ratio of individual 22CH03 exhibited a temporary increase exceeding 3, whereas the ⁸⁷Sr/⁸⁶Sr ratio of the individual remained stable at approximately 0.71053, confirming that this individual had a freshwater life history. In contrast, the otoliths of individual 22CH07 displayed sharp fluctuations in Sr/Ca ratios, rising to 5.37±0.57 after a low Sr/Ca ratio region near the core, and decreasing to less than 3 at the edge. This pattern indicated that the individual was born in freshwater, grew in the estuary, and returned to freshwater, reflecting a migratory life history. The ⁸⁷Sr/⁸⁶Sr ratios of the otoliths of 22CH07 were initially high at 0.71451, corresponding to the region with high Sr/Ca ratios and higher than the water of Chaohu Lake and its tributaries. This suggests that this fish originated from Poyang Lake. Subsequently, the ratio decreased to 0.70945, aligning with regions with high Sr/Ca ratios, indicating an estuary and nearshore life history. At the otolith margin, the ratio decreased to 0.71079, which was close to the background 87Sr/86Sr ratio of Chaohu Lake. These results indicated the presence of one anadromous C. nasus individual in Chaohu Lake, likely originating from Poyang Lake. This suggests that Chaohu Lake maintains connectivity with the Yangtze River to some extent. Additionally, owing to the small sample size of this study, further investigation is needed to determine whether an anadromous C. nasus population exists that is both born and reproduces in Chaohu Lake.