To investigate billfish and tuna movement patterns, pop-up satellite archival tags (PSATs) were deployed using the traditional tuna longline fisheries of southeastern Taiwan (Taitung). Depth, temperature and ambient light data were recorded by the PSATs. In total, 2 swordfish and 4 bigeye tuna were tagged between Dec 2017 to Nov 2018 and PSATs remain affixed from 14 and 20 days-at-liberty from swordfish. Linear displacements ranged from 631 and 1605 km from deployment to pop-up locations. Diving depths ranged from the surface to 914.5 and 559.5 m and water temperatures occupied ranged from 26.7°C to 4.9°C. Bigeye tuna, after 47 days-at-liberty, the PSAT was physically retrieved and in aggregate. The linear displacement was 269.4 km from deployment to pop-up location. After tagging the bigeye tuna moved south, but we did not find large-scale movement. Habitat depth and experienced temperatures ranged from 0 to 1,036 m and from 26 - 4.2 °C, respectively. Swordfish and bigeye tuna the distributions of time spent at depth were significantly different between daytime and nighttime and at dusk, the fish ascended into the surface layer and remained there until the following dawn. Swordfish and bigeye tuna follow the diel vertical movements of prey organisms comprising the deep sound scattering layer (SSL) to exploit them effectively as a resource and can maintain their body temperature for longer periods below the thermocline. Because of its unique physiological and morphological adaptations (such as vascular countercurrent heat exchangers) it can search for food resources more effectively than other fishes.