Bycatch and discards by Taiwanese large-scale tuna longline fleets in the Indian Ocean

摘要: Conservation of ecologically related species and understanding the discard composition fisheries are major concerns for marine ecosystem conservation. However, high sea longline data insufficient because difficulties in deploying observers collection. Observer collected from 77 trips on Taiwanese large-scale fishing vessels Indian Ocean June 2004 to March 2008 were used estimate scale bycatch. At least 40 recorded. Albacore, bigeye, yellowfin, southern bluefin tuna recorded comprised over 73.30% total retained catch. Major bycatch swordfish, blue shark, sailfish, pomfret, escolar. The average rate was 14.09%, ranging 3.20% yellowfin fleet 18.09% bigeye fleet. In total, 0.80% catch albacore, 4.74% 2.32% discarded. There significant differences among seasons areas rates tuna. positively correlated per unit effort. depredation percentage by cetaceans 0.7% 12.3% discards different fleets. cetacean showed that possible reasons cetaceans, economic factors, quota limitations. Regarding other species, 61 seabirds 84 turtles a part Yellow-nosed Albatross Olive Ridley tropical areas. estimated annual incidental numbers 715 311 1856 1127 2007. For conservation, this information could be assess stocks. Mitigation measures, including live release small-sized fish, use bird-scaring lines circle hooks, required minimize