Population ecology of landlocked ayu in Kasumigaura Lake system and its utilization and conservation

霞浦湖水系内陆香鱼种群生态及其利用与保护

• 批准号: 16580157
• 负责人: IDA Hitoshi
• 金额: $ 1.28万
• 依托单位: Kitasato University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16580157/
• 关键词: Kasumigaura Lake system; landlocked ayu; Gompertz growth curve; gill raker length; stomach contents; stable isotope; otolith; microsatellite DNA; 霞ヶ浦; アユ; 陸封; 安定同位体比; 形態

Growth analysis using otolith microstructure, genetic analysis using microsatellite DNA, gut contents analysis and morphological comparison with different stocks were conducted on landlocked ayu population in Kasumigaura Lake system. Stable isotope analysis was also applied to estimate consumed food items. As a unique property of otolith microstructure, Kasumigaura ayu has transparent zone which lacks daily ring. Therefore it is difficult to determine hatched date from daily ring counts. We found daily increments of otolith correlated with water temperature and when increments decreased below 1mirco meter, transparent zone started to form. The formation of transparent zone lasted from middle January to late February. Estimated hached dates were distributed from late September to late November both for 2000 and 2001 samples. When hatched dates were compared between two samples taken from September to January and from February to April, difference was seen only for 2000 samples. As estim … More ated hatched dates were later for September to January sample in 2000, the survival of early hatched ayu juveniles was suggested to be low in 2000. The early growth of juveniles estimated based on backcalculation was well fitted for Gompertz growth curve. From the observation of stomach contents of juvenile ayu, prey items and size were altered at 2cm total length. This change was thought to be related with the shift of developmental stage occurring at 2cm total length. Microsatellite DNA analysis revealed that Kasumigaura Ayu differed from nearby amphidromous population at Pal5 locus. From stable isotope analysis carbon isotope values for within lake ayu were more depleted than upstream migrated ayu, and nitrogen isotope values were high for within lake fish, low for upstream migrated fish. This observation was well correspond to the observation that within lake ayu depend on zooplankton, but on attached algae for upstream migrated ayu. Gill raker length of Kasumigaura ayu caught in 1960s was long as same as nowadays Kasumigaura ayu. Less

对霞浦湖系内陆香鱼种群进行了耳石显微结构生长分析、微卫星DNA遗传分析、肠道内容物分析以及不同种群的形态比较。稳定同位素分析也用于估计消耗的食物项目。耳石微结构的一个独特特征是耳石透明带，不存在日轮。因此，很难确定孵化日期从每天的戒指计数。发现耳石的日生长量与水温有关，当日生长量低于1微米时，透明带开始形成。透明带的形成从1月中旬持续到2月下旬。2000年和2001年样品的估计hached日期分布在9月下旬至11月下旬。在比较9月至次年1月和2月至次年4月的两个样本的孵化日期时，仅2000个样本存在差异。估计数 ...更多信息 2000年9月至1月的样本中，早期孵化的香鱼幼鱼存活率较低。反算估算的幼鱼早期生长与Gompertz生长曲线拟合较好。通过对香鱼幼鱼胃内容物的观察，发现在体长2cm时，猎物的种类和大小都发生了变化。这种变化可能与全长2cm时发生的发育阶段转移有关。微卫星DNA分析表明，霞浦香鱼与邻近的两个无转群体在Pal 5位点上存在差异。从稳定同位素分析来看，湖内香鱼的碳同位素值比上游洄游香鱼的碳同位素值更低，湖内鱼类的氮同位素值高，上游洄游鱼类的氮同位素值低。这与香鱼在湖内主要依靠浮游动物生存，而向上游迁移的香鱼主要依靠附着藻类生存的观点相一致。20世纪60年代捕获的霞浦香鱼鳃耙长度与现在的霞浦香鱼相当。少