| 英文摘要 |
This purpose of this study is to estimate the impact of Taiwanese tuna longline fisheries on ecological related species, included seabirds, sea turtles, and cetaceans as well as the depredation by cetaceans and sharks in the Indian Ocean. Two sources of data have used in this research, the observer’s data and Task 2 data from distant water longline fishing vessels operating in three oceans from 2004 to 2007. The results and recommendations are as follows,
?The seabird bycatch were mainly concentrated in high latitude, especially in North Pacific Ocean and South Eastern Atlantic Ocean. The total estimated bycatch numbers were around 4,500 globally. Considering that many RFMOs have requested fishing vessels to set the bird scaring measures, it is recommended to further analyze the effect of bird scaring lines and other mitigation measures.
?The bycatch of sea turtles have frequently happened in tropical Atlantic Ocean, the preliminary estimate bycatch number were around 4,000 in three oceans annually. It is recommended to promote the using to circle hooks in Atlantic Ocean, for decrease the impact of tuna longline fisheries on sea turtles.
?As for the cetaceans, the bycatch rate is low. The estimated bycatch were around 120 per year. The data collection should be continued.
?The depredation rate by cetaceans and sharks of total catch was around 0.85-2.01% in Indian Ocean. The bigeye tuna depredation rate was as high as 3.10 % in tropical area. The estimated bycatch, including discards were around 2,000 mt per year.
?Observer program has its important role on collecting data for stock assessment on target species as well as for bycatch species. For ensure the data could be more representative on the actual fisheries activities, it should be considerate on sampling strategy, not only using random stratification sampling, but also consider to deploy more observers on those area with higher bycatch rate. |