This dataset is derived from ten surveys with a total of 20 otter trawling sessions conducted at the Changyun Rise off the western coast of Taiwan between 2017-2018 and 2020-2021. The surveys were conducted at two sites, inshore (15-25 m depth) and offshore (40-50 m depth), utilizing a commercial otter trawling boat prior to the commencement of the offshore wind farm development. The dataset includes 8,026 individual fish, encompassing 51 families, 84 genera, and 128 taxa. Not only did the composition and abundance (ind./104m2) of fish species significantly differ between the inshore and offshore sites, but spatiotemporal variation was also observed in dominant fish species between 2017-2018 and 2020-2021. This dataset serves as a baseline for demersal fish prior to the development of the Changhua offshore wind farm. It offers critical information for subsequent environmental impact assessments, proposing mitigation measures, and establishing continuous monitoring networks.