摘要：大目鮪已成為WCPO最可能優先進行配額管制的魚種，未來大目鮪若採取配額分配或體長限制等管理措施(大西洋1980年即以實施)，則熱帶地區之圍網混獲問題將成為保育上的漏洞。如何在圍網作業階段中，採取減緩混獲大目鮪幼魚的作為，將成為繼海豚混獲問題之後，圍網漁業永續經營上必須嚴肅面對的問題。本研究擬在圍網捕撈FAD作業之探魚與集魚階段先行判別，透過聲探理論、水槽實驗及現場實驗進行魚探信號的分析，以分辨FAD聚集魚群的屬性，研究減緩混獲可能之道。 Abstract:Bigeye tuna may become the first tuna species of quota-control in the WCPO. If quota or minimum length of catch were applied in the future, the bycatch of juvenile yellowfin and bigeye tuna caught by purse seine will turn to be a key problem. How to reduce bycatch of them is therefore a serious crisis being faced by purse seine fishery after dolphin issue in the past. This study plan to identify the condition of fish aggregated by FAD prior to fishing action. With the acoustic theory, measurement in cage (optional) and in-situ experiments, this study aim to analyse the features of echograms/signals collected by echo sounders to differentiate characteristics of schools aggregated by FAD. Then, brought up the possible way to reduce the bycatch of the juvenile yellowfin and bigeye.