Seabirds and sea turtles bycatch of Taiwanese tuna longline fleets in the Pacific Ocean

To understand the sea turtle and seabird bycatch of Taiwanese distant water longline fleets for conservation purposes, this research analyzed the data collected by observers onboard between 2008 and 2013. In total, the bycatch data from 149 trips and 24.3 million hooks were collected, including 50 albacore large-scale tuna longline vessels (LSTLVs) trips, 72 bigeye LSTLVs trips, and 27 small-scale longline (SSTLVs) trips. The observer coverage rates of LSTLVs varied between 4.70% and 7.95% by year. The seabird bycatch was mostly from albacore LST LVs, followed by bigeye LSTLVs but that of the SSTLVs was very low. The highest bycatch rate was 0.318 birds per thousand hooks in the Southwest Pacific Ocean in the first quarter, followed by the same area in the second quarter (0.046 birds per thousand hooks). For seabird bycatch species, 82% were albatrosses, including wandering, black-footed albatrosses; and petrels, shearwaters, and booby. The estimated annual bycatch numbers ranged from 175 to 381 between 2008 and 2013 for LSTLVs. As for sea turtles, the bycatch rate of SSTLVs was higher than that of LSTLVs. The major bycatch species were olive Ridley turtle, followed by green and leatherback turtles. The sea turtles bycatch rate peaked in the second quarter in the western tropical Pacific Ocean (0.011 turtles per thousand hooks), followed by the fourth quarter (0.006 turtles per thousand hooks). The estimated sea turtle bycatch numbers ranged from 131 to 249 per year between 2008 and 2013 for LSTLVs.