"日本鰻河川放流後之成長,銀化與遷徙研究"

Abstract

日本鰻是東亞水產養殖的重要魚種之一近年來鰻魚資源面臨嚴重的資源短缺，因此如何管理與復育日本鰻資源，便成為鰻魚產業永續發展的關鍵。雖然過去台灣進行過多次鰻魚的標幟放流，但顯少有研究試圖探討放流後鰻魚在野生環境的情形。為建立日本鰻放流之標準作業程序，並提供基礎資料做為未來資源復育的參考，本研究擬討論放流鰻於野外的成長、銀化及洄游行為。本實驗室與農委會水產試驗所合作，選定鳳山溪、宜蘭河以及高屏溪，總共實行兩次標幟放流。第一次於2010年12月放流至三條河川，第二次於2011年5月放流至宜蘭河。回收結果顯示，成鰻回收率初期較高，經三個月後逐漸降低；鍶鈣比分析與鰻魚回收地點的結果則指出部分放流鰻會留在放流點附近或是移動至下游，而大多數放流鰻則偏向棲息於淡水或是稍有鹽度之水域。放流鰻魚在放流三、四個月後體型開始有增加之趨勢。生理指數也顯示，放流銀鰻之發育情形與野生銀鰻相似，且從回收率可推測部分銀鰻在四月前應已降海。綜上所述，放流鰻於放流後可適應野外環境，且降海洄游之策略與野生成鰻相似。

Japanese eel (Anguilla japonica) is an important aquaculture species in East Asia. The resources of Japanese eels suffer serious shortage in recent years. Thus, the management and recovery of eel stock is a key point for the sustainability of eel aquaculture industry. However, in Taiwan many eel stock released have been done before, few studies were attempted to examine the circumstances of released eels in the wild after released. In order to establish a standard operating procedure for stock releasing and provide a basic information for reference, this study aims to understand the growth, silvering and migratory of released eels in the wild. In December 2010, our laboratory and the Fisheries Research Institute marked and released stock elvers and adult eels in Fengshan River, Kaoping River, and Yilan River. In May 2011, it was down another batchin the Yilan River. Results of the recapture showed that the recaptured rate of adult eels was higher in the beginning, but became lower after 3 months. Based on the Sr:Ca ratios and recaptured sites, some released eels did not leave the releasing sites and some of them moved to the down reaches. Most of them stayed in the freshwater or the brackish water. The released eels could increase their size after 3-4 months of releasing. The physiological indicators of recaptured silver eels were slimier to those of the wild silver eels. The released silver eels might migrate to the sea before April. In summary, the released eels are possible to adapt the wild environment, and the downstream migration strategy of released adult eels seems to be similar to that of wild ones.