| Summary: | 碩士 === 臺灣大學 === 漁業科學研究所 === 96 === 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.
|
|---|
