利用耳石化學元素中鎂及錳差異判別放流與野生黑鯛之研究

Abstract

近年來沿近海漁業資源減少，政府及民間組織著手進行資源復育，而以魚苗放流作為增裕漁業資源的手段之一。然而欲評估放流之效果，判定野生與人工養殖放流魚是相當重要的工作。人工養殖放流魚生活史初期是在人工養殖環境下生長，繁養殖業者經常使用地下水作為部分的淡水水源，此一差異應可反映在耳石的元素組成上。一般而言，人工養殖魚若使用地下水，其鎂含量在耳石核心部分會比邊緣部分高，而錳含量則在核心部分較低。 本研究於2005.7.21-9.23期間，在苗栗縣通宵鎮白沙屯海域經雙重標識(先投餵含四環黴素飼料後再使用噴槍將螢光色素噴在魚的表皮)後，放流5公分左右黑鯛魚苗約十萬八千尾，並以6尾未放流至海中之人工養殖黑鯛與3尾放流再捕黑鯛的耳石化學組成為基礎，建立海洋中捕獲黑鯛來源的判別依據。 共分析判斷10尾海中捕獲且體表無標識之黑鯛，結果顯示6尾的耳石核心部分，鎂含量較邊緣高，呈現近似於倒V字型的分佈，另3尾的耳石核心部分錳含量較低且周圍有較高値，呈現近似於U字型的分佈，其他樣本則無明顯不同。故推測海中捕獲且體表無標識之黑鯛中，6尾可能為放流再捕魚，4尾可能為野生魚，結合鎂及錳兩元素之可判讀率為60%。據此結果將可進行過去未經標識放流的黑鯛之放流效果評估。

Due to the decreasing of the inshore and offshore fishery resources, the fry had been released to enhance their stock by many organizations in recent years. The discrimination of wild and hatchery-reared individual have to be done before the assessment of released efficiency. Ground water usually used to take the partial fresh water source in numerous hatchery at early life stage of hatchery-reared fish, so that elements composition of otolith may be different. Generally, the value of otolith magnesium in nucleus zone may be higher than that of edge zone, while the value of otolith manganese in nucleus zone may be lower than that of edge zone. This study released around one hundred and eight thousands black porgy fries about 5cm, which were double marked (spraying with fluorescent pigment on the skin after fed with tetracycline) to Baishatun coast in Miaoli County during July 21 to September 23 in 2005. The discrimination criteria of captured black porgy were establish, according to six black porgy that hatchery-reared and never released to the sea, and three recaptured marked individual. The otolith elements of ten recaptured individual were analyzed. Among six, their otolith nucleus zone showed higher magnesium than that of the edge zone, the distribution is similar to an inverse of V, while three otolith nucleus zone showed lower manganese than that of the edge zone and had high value around nucleus zone, the distribution is similar to an U. Others didn’t show obvious trend. That is, four individual may be hatchery-reared fish, four individual may be wild fish, and one individual were confused. Their correct classifying rate is about 60%. It is suggested that the efficiency of previous released black porgy without any marking can be assessed using this method.