In this study, length-frequency and sex ratio (proportion of females) of dolphinfish were analyzed based on 95,714 (59,896 were females and 35,818 were males) samples measured in Shingkang fish market during 2003 to 2020, and catch compositions of dolphinfish longline fishery were also explored based on the catch records collected from Shingkang fish market during 2017 to 2020. There were significant differences in the length and sex ratio of the catches in the two seasons, with the length of the catch in summer being significantly greater than that in winter. However, there are two recruitment to eastern waters of Taiwan from July to August and October to December. The sex ratio shows that females are dominant, with a total ratio of 0.62. The proportion of male becomes higher than females when body length increased. The results of this study indicated that fishing exploitation might have led to the decreases in the body size in recent years. The 85.1% of the catch dolphinfish for dolphinfish longline, the by-catch are only 14.9%, and the monthly by-catch shows that the between 8.9-23.9%, which during the fishing season of dolphinfish the by-catch from March to May and October to December were 14.9-16.6% and 8.9-13.2% respectively, indicating that the by-catch during the fishing season of dolphinfish was lower than other months. The dolphinfish longline vessel option area distribution off Singang waters of months, but gradually move north to Hualien coastal waters in winter. Pop-up satellite archival tags (PSATs) were deployed on four dolphinfish (94–102 cm fork length), caught using set-nets in the northern East China Sea. Tagged dolphinfish retained PSATs for 5–31 days-at-liberty (total 69 days) and linear dispersion from deployment to pop-up locations ranged from 63 to 204 km. According to most probable tracks, tagged fish made primarily northward movements. Tagged fish reached depths of ~94 m and experienced ambient temperatures from 17.8 to 23°C. The cluster analysis suggests a clinal trend of distinct thermal clusters with limited mixing among locations. Our preliminary results provide dymainc of dolphinfish longline fishing ground and movement patterns of dolphinfish in a location that supports important fisheries. This information will be useful for management to develop stock assessments which support the sustainable use of this species.