Abstract Taiwan is an island country, the topography of the adjacent territorial waters is diversified, multiple ocean currents converge here and there are rich basic production capabilities, all of which give birth to various marine organisms in Taiwan and help to form the favorable conditions for Taiwan to develop its offshore fishery. However, due to the lack of control of the production capabilities of offshore waters in the last few decades, plus the constant upgrading of fishing techniques and methods, as well as the lack of effective management, the fishery resources have been greatly impacted and the total fishery production continues to decline. Fishery resource management needs correct fishing location, fishing effort and catch totals as the scientific basis for fish stock assessment, in order to achieve effective management targets. The greatest problem for the offshore waters of Taiwan is that we could not obtain detailed information on the fishing location, operation time (fishing effort) and catch totals. At present, the above data were all obtained through investigations or by interviewing with captains to fill in report forms. However, out of fear of disclosing trade secrets and owing to omissions, the obtained data could not help in revealing the real fishery resource situation. The Coast Guard Administration of the Executive Yuan integrally established a coast radar system along the coast of Taiwan, which monitors all ships within the scanning area through 24-hour uninterrupted scanning, and digitally records the navigation data on ships. The data contains time, ship number, speed, course, latitude and longitude (location); by sorting out these data, we could discern the actual fishing location of the fishing boats. The objective of this study was to utilize the data collected by the coast radar system to determine the fishing location of the fishing boats, acquire the port entry and exit data of the fishing boats through the security examination system, work out the fishing effort, and by collecting the catch and sales data from five fishery harbors, derive the respective total amount of the 10 main fish species caught, in order to investigate the fishery dynamics of Southern Taiwan sea. Research results show that by applying the coast radar system along with the use of port entry and exit data on the fishing boats recorded in the security examination system, as well as the catch and sales data of the fishing boats, and through comparison of the above data, we could obtain proper estimations of fishing effort and fishing location of the fishing boats, as well as the catch per unit effort (CPUE) and the distribution of species composition. Keywords: coast radar, Tainan coastal and offshore fisheries, fishing effort, fishing location¡Acatch per unit effort