| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋事務與資源管理研究所 === 99 === Following the international trend on marine resources conservation, Food and Agriculture Organization of the United Nations and many Regional Fisheries Management Organizations adopted measures for conservation of important incidental catch species, include seabirds, sea turtles, sharks and marine mammals. Those organizations recommend related countries shall collect data and implement conservation and management measures. Among those data collection method, observer program could provide detail incidental catch information for evaluate the fisheries impacts on those bycatch species. However, not all fishing vessels could deploy observers because of budget limitation. The objective of this research is to discuss the observer coverage by control the coefficient of variance (CV) of catch per unit effort (CPUE), to improve the precision.
One hundred and sixty eight trips of Taiwanese distant water longline vessels observer trips data from 2004 to 2007 were used for analysis. The catch per unit effort (CPUE) of target species and bycatch species (including sharks, seabirds, seaturtles, and cetaceans) are used for spatial and temporal stratification. Bootstrap is used to estimate the CPUE and CV for each stratum under different observer coverage from 1% to 100%. The key conservation species are selected in accordance with their distribution. The observer coverage rate of key species under the CV =30% are considered as the minimum requirement for observer coverage requirement. In addition, the request from Regional fisheries management organizations, and total observers day are considered as well.
The results showed thirteen sub-regions are separated. Among these sub-regions, south Atlantic Ocean and southwest Indian Ocean are further separated by seasons because the data are more than 30 in each stratum and the CPUE of key species are significant difference for seasons. Among these strata, the coverage rate ranged from 50% (first season of south Atlantic Ocean for seabirds) to 1% (second season of south Atlantic Ocean, central Atlantic Ocean, northwest Pacific Ocean, southwest Pacific Ocean and first season of southwest Indian Ocean). The total observer days is 9548 days based on the number of observers was 62. We could control the CV at 25% for three oceans; which the coverage rate was 7.33% for Atlantic Ocean, 15.7% for Pacific Ocean, and 11.81% for Indian Ocean. Among these sub-regions, the observer coverage rate was highest in central western Pacific Ocean (55%), and the lowest in the southeast Indian Ocean (4.58%).
In conclusion, it is not necessary for all areas to deploy 5% observer to ensure the CV less than 30%. The central Atlantic Ocean, second and third season of south Atlantic Ocean, northwest and southwest Pacific Ocean could have less observer coverage. The additional observer could reallocate to other area, such as first season of south Atlantic Ocean, central western Pacific Ocean and northeast Indian Ocean. In the future, when deploying the observer, shall considered the data precision, total capacity of observer program and request from regional fisheries management organizations.
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