International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Otsuchi, Iwate, Japan.
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan.
PLoS One. 2019 Sep 4;14(9):e0222052. doi: 10.1371/journal.pone.0222052. eCollection 2019.
To understand the ecology of juvenile chum salmon during early marine life after their downstream migration, we developed a quantitative PCR-based environmental DNA (eDNA) method specific for chum salmon and investigated the spatiotemporal distribution of eDNA in Otsuchi Bay, Iwate, Japan. Indoor aquarium experiments demonstrated the following characteristics of chum salmon eDNA: (1) the eDNA shedding and degradation were time- and water temperature-dependent and the bacterial abundance could contribute to the eDNA decay, (2) fecal discharge may not be the main source of eDNA, and (3) a strong positive Pearson correlation was found between the number of juveniles and the eDNA amounts. As we discovered strong PCR inhibition from the seawater samples of the bay, we optimized the eDNA assay protocol for natural seawater samples by adding a further purification step and modification of PCR mixture. The intensive eDNA analysis in the spring of 2017 and 2018 indicated that juvenile chum salmon initially inhabited in shallow waters in the shorefront area and then spread over the bay from January to June. The eDNA data also pointed out that outmigration of juvenile chum salmon to open ocean temporarily suspended in April, possibly being associated with the dynamics of the Oyashio Current as suggested by a previous observation. The eDNA method thus enables us large-scale and comprehensive surveys without affecting populations to understand the spatiotemporal dynamics of juvenile chum salmon.
为了了解幼鲑鱼在洄游下游后早期海洋生活期间的生态，我们开发了一种基于定量 PCR 的环境 DNA (eDNA) 方法，该方法针对鲑鱼，并调查了日本岩手县大槌湾的 eDNA 的时空分布。室内水族馆实验证明了鲑鱼 eDNA 的以下特征：（1）eDNA 的脱落和降解与时间和水温度有关，细菌丰度可能导致 eDNA 衰减，（2）粪便排放可能不是 eDNA 的主要来源，（3）幼鱼数量与 eDNA 量之间存在强烈的正皮尔逊相关关系。由于我们发现湾内海水样本存在强烈的 PCR 抑制，因此我们通过添加进一步的纯化步骤和对 PCR 混合物的修改，优化了自然海水样本的 eDNA 检测方案。2017 年和 2018 年春季的密集 eDNA 分析表明，幼鲑鱼最初栖息在海滨地区的浅水区，然后从 1 月到 6 月在整个湾内扩散。eDNA 数据还表明，幼鲑鱼向开阔海洋的洄游在 4 月暂时停止，这可能与之前观察到的亲潮动力有关。因此，eDNA 方法使我们能够在不影响种群的情况下进行大规模和全面的调查，以了解幼鲑鱼的时空动态。
