Yellowfin tuna is the main target species of longline fishery in
offshore waters off Taiwan. The main fishing ground were in the south
China sea, it is very important fishery resources. The period longline
fishery operations during September to November in the southwestern
waters of Taiwan. In this study, we compile the environmental factors
a n d c a t c h d a t a t o d i s c u s s t h e C P U E v a r i a t i o n , a n d
regularly to measurements the yellowfin tuna fork length, body weight in
the Dong-Gang fish market and experimental longline operations
investigate by the fishing boat to optimum catch depth.