|Abstract: ||2006年7月南方黑鮪保育委員會(CCSBT)特別委員會議中調查小組報告指出日本市場及澳洲養殖未回報產量異常現象，且在同年9月第七屆資源評估會議評估未回報捕獲量對資源評估可能情境的模擬結果，證明若未來總可捕量維持2006年14,925公噸的水準，則2014年產卵母族群回復至2004年水準的資源回復機率只有3%，遠低於2005年資源評估會議所訂定至少有50%之機率的短期目標，故2006年CCSBT年會決議2007至2009年間總配額減少為11,530公噸。 本研究應用CCSBT 資源評估運作模型模擬分析上述短期配額減量，證實2014年產卵母族群量不低於2006年水準之機率僅提升至24.75%至35.4%，未達2005年所訂定資源回復目標。此外，本研究並進一步採用2005年資源評估會議所認定四套候選決策原則中表現較佳之CMP_2與CMP_4，模擬2010年至2011 或2013及2014年起不同期程啟動管理程序對未來資源回復機率的效果。研究發現CMP_2短期內缺乏調整配額之機制，以致不論啟動管理程序期程，2014年資源量於最低點時皆未達2005年所訂定之短期永續目標，2022年資源量僅回復為2006年的1.29倍，遠低於2005年資源評估會議所認定之長期資源回復水準1.9倍。CMP_4則愈早啟動管理程序會使資源的回復愈好，亦即可根據未回報捕獲量即時調整配額，使資源量盡可能符合資源適度利用的目標，且2022年資源量達2006年的1.53倍，較符合2005年所訂定之長期資源回復目標。研究結果提供CCSBT未來早執行管理程序時參考的依據，並建議需盡早調降配額數量，以期能符合資源之回復，達到資源適度利用的目標。|
Two independent panels on the Special Meeting of the Extended Commission of CCSBT indicated in July 2006 that anomalies in the Japanese SBT market data and the Australian SBT farming operation data. In September, 2006 meeting of the 7th CCSBT Stock Assessment Group (SAG), simulation evaluation of the possible unreported landings under various scenarios were reported. In addition, it was demonstrated that, under the assumption that future Total Allowance Catch (TAC) is kept at the same level as in 2006 of 14,925 MT, the estimated that the probability that the spawning biomass in 2014 will be more than the level in 2004 is only 3% and the spawning biomass will be severely depleted in the short run. It is much lower than the level set by the consensus of the 2005 SAG meeting that there should be at least a 50% probability that the biomass in 2014 is no less than the level in 2004. Hence, in the 2006 annual meeting, a resolution was passed to reduce the TAC to 11,530 MT from 2007 to 2009. This study utilizes the CCSBT stock assessment operation model to conduct simulations of the reduction of TAC to 11,530 MT since 2007. The results shows that the probability that the spawning biomass in 2014 is no less than the level in 2006 is between 24.75% and 35.4%, which is still below the resource sustainability target set in 2005. Further, we use CMP_2 and CMP_4, two preferred rules from four candidate decision rules recommended by the 2005 Stock Assessment Meeting, to simulate the impact on future stock recovery rates when the management procedures are started in 2010, 2011, 2013 or 2014. The simulation result shows that CMP_2 is unable to adjust quota in the short run when the stock reaches the lowest level in 2014 and the stocks in 2022 will be 1.29 times of the 2006 level, far below the 1.9 times target set by the 2005 Stock Assessment Meeting for long term stock recovery. Regardless when the management procedure is initiated, the sustainability targets set in 2005 cannot be reached in all circumstances. On the other hand, under CMP_4, the earlier the management procedure is initiated, the better will be the stock recovery. In other words, quota is adjusted as soon as the unreported catch is given, allowing the resource stock to reach the targeted level and the stock in 2022 will be 1.53 times of the 2006 level, much closer to the long run stock recovery target as specified in 2005. The research findings offer the recommendion to CCSBT in future to initiate the management procedure and to adjust TAC as sooner as possible in order to meet the target of stock recovery and the objective of optimal utilization.