| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 98 === Traditionally ICCAT uses the surplus production model (e.g., Schaefer 1957) to calculate the biological reference points when performing stock assessment on the southern Atlantic swordfish stock, but the growth and mortality between the age classes cannot be explained by this single production function. In this study, a age-structured production model (ASPM) which can include the information of selectivity, weight-at-age, maturity-at-age and natural mortality information was used for the stock assessment of swordfish in the South Atlantic Ocean. The ASPM model was fitted to the catch-rate data for the Japanese, Taiwan, Spain, Brazil and Uruguay longline fisheries, as these fleets take the bulk of the catch of swordfish in the Sorth Atlantic Ocean. The results of this study showed that the Southern Atlantic swordfish stock’s was slightly overfished by F2008/FMSY equal to 0.89 and SSB2008/SSBMSY was slightly smaller than 1（0.91）. A total allowable catch of 11,000 tons or <11,000 tons was suggested to recover stock status for the projected fifteen years. Monte Carlo simulation was used to evaluate the impact of errors in input parameters on the quantities of management interest. The sensitivity analysis showed that errors in natural mortality, CPUE, and catch have the substantial effect on the stock status evaluations. Future research on these fields is highlight and should be enhanced to reduce the uncertainty of the stock assessment.
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