南方黑鮪全球總可捕量管理程序臺灣決策原則之評估

EVALUATION OF THE TAI DECISION RULES OF THE MANAGEMENT PROCEDURE OF TOTAL ALLOWABLE CATCH OF SOUTHERN BLUEFIN TUNA

為保育與最適利用南方黑鮪的資源， 南方黑鮪保育委員會（CCSBT） 自2000 年起開始發展管理程序（management procedure， MP）， 以制定一套明確且透明之全球總可捕量（total allowable catch， TAC） 機制。CCSBT 於2004 年5 月第三屆管理程序會議建構1969 年至2000 年南方黑鮪年齡結構化資源動態運作模式（operating model）， 用以模擬至2032 年間之漁業資源狀態之參考模組（reference set）， 測試在不同資源回復目標下， 各套決策原則（decision rule） 如何動態調整訂定TAC。最後， 篩選出四套表現理想之決策原則做為未來執行MP 之決策選項， 其中TAI 03 決策原則為臺灣科學家代表所發展，為依CPUE變動率及漁獲量與魚價波動之逆需求彈性調整TAC之決策原則。依CCSBT決議於2005年2月管理程序特別技術會議將資源動態運作模式更新至2003年，本研究首先依更新後之參考模組，進行模擬TAI 03決策原則的表現， 並進一步設定TAI 04 決策原則以降低TAC 跨期變異程度， 及設定TAI 05決策原則以短、中、長期三段不同期間的設定調整TAC，以期兼顧資源保育及產業穩定經營並於2005年5月第四屆管理程序會議提供此TAI 05決策原則，以進行四組候選決策原則之再評比。本研究模擬結果顯示， TAI 05 決策原則為四套候選決策原則中考量短期內緩降TAC 以提供產業逐漸移出的機會， 有效降低TAC 跨期變異程度， 降低產業所面對總收益的不確定性， 並將長期資源匱乏之風險值控制在較低的水準， 期以兼顧資源保育及漁業經濟活動， 避免短、中、長期間社會經濟層面無謂的損失。

The Management Procedure of Southern Bluefin Tuna (SBT) was developed since 2000 by the Commission for Conservation of Southern Bluefin Tuna (CCSBT) to conserve and ensure optimum utilization of the global SBT fishery through a transparent mechanismfor deciding the global total allowable catch (TAC). According to both the official report of CCSBT for the third Meeting of the Management Procedure Workshop in May 2004, the Age-Structured Population Operating Model (OM) was established by utilizing the harvest data from 1969 to 2000 and was used to simulate the future trajectory reference set of the biomass and total allowable catch (TAC) till 2032. Four candidate decision rules (DR) were selected to decide the appropriate TAC trajectory under various scenarios in order to achieve the recovery target of the biomass. Among the final four candidate decision rules, TAI 03, proposed by Sun (2004), is a CPUE-based DR with a negative built-in feedback component in terms of the theoretical economic consideration of the inverse relationship between price and demand. This study tries to apply the TAI 03 decision rule on the updated Reference Set which is updated by the scientific advisory panel with harvest data until 2003 in February 2005. This study specifies the TAI 04 decision rule to reduce the interannual variation of TAC and the TAI 05 to adapt to the short-term, intermediate, and long-termsituation in order to take into account both sustainability of resource management and industry operation. The simulation result of the TAI 05 decision rule was compared again with the other three candidate decision rules during the fourthmanagement procedure workshop in 2005. The simulation results show that the TAI 05 decision rulewould adjust TAC gradually for the industry to followand to reduce the uncertainty in revenue in the short-term and to reduce the risk of resource deterioration and to fulfill the requirement that both the recovery of the biomass and the optimum utilization of the global SBT fishery in order to avoid the economic deadweight loss in the long run.