應用非平衡生產量模式評估太平洋黑鮪系群

Abstract

太平洋黑鮪(Thunnus orientalis)為一種高經濟價值的溫帶鮪類。從1950年代起，即開始對於該資源進行開發利用，而每年的漁獲量也逐漸增加。在北太平洋主要的作業國家有日本、韓國、台灣、美國及墨西哥；而捕撈的漁法有圍網、延繩釣、曳繩釣、一支釣、定置網及拖網。本研究蒐集1952至2006年北太平洋主要漁業的漁獲量(catch)及單位努力漁獲量(CPUE)，利用非平衡生產量模式(non-equilibrium production model)對太平洋黑鮪進行資源評估。 估計所得T.orientalis的最大持續生產量(MSY)介於19,000至26,000噸之間。利用估計所得的MSY進行15年的模擬，發現若將每年的漁撈水準(catch level)設定大於18,000噸時，15年後的資源量會接近或小於達到MSY所需的資源量(B_MSY)，並且將會大於達到最大持續生產量(MSY)的漁獲死亡率(F_MSY)。因此，建議將T.orientalis的最大容許漁獲量(TAC)設定在小於18,000噸。

Pacific bluefin tuna (Thunnus orientalis) is a temperate tuna with highly economic value. The exploitation of Pacific bluefin tuna began in 1950s and was mainly utilized by Japan, Korea, Taiwan, United States of America and Mexico in the North Pacific Ocean and the fishing methods are mainly purse seine, longline, troll, pole and line, set net and trawl. In this study, I gathered catch and CPUE data of these fisheries from 1952 to 2006 and used the non-equilibrium production model for stock assessment of T. orientalis. The estimated maximum sustainable yield (MSY) by non-equilibrium production model is between 19,000 ~ 26,000 metric tons. From projection results, the biomass of T.orientalis would be closer or lower than biomass at MSY (B_MSY) and fishing mortality would exceed fishing mortality at MSY (F_MSY) if catch level greater than 18,000 MT. So suggest setting total allowance catch (TAC) of Pacific bluefin tuna smaller than 18,000 metric tons.