Abstract

The Japanese scad Decapterus maruadsi (Carangidae) is an economically important marine species in Asia but its exploitation shows signs of overfishing. To document its stock structure, a population genetic and phylogeographic study of several populations of this species from the central part of the Indo-West Pacific region was conducted using the mitochondrial cytochrome b gene. Genetic homogeneity within the Sundaland region’s population, including Rosario (the Philippines) and Ranong (Andaman Sea) populations was revealed with low nucleotide diversity (π = 0.001–0.003) but high haplotype diversity (h = 0.503–0.822). In contrast, a clear genetic structure was observed between this group and the northern Vietnam populations as revealed by F _ST, AMOVA and SAMOVA, while the central Vietnam population of Khanh Hoa is an admixed group between the two differentiated regional populations. The neutrality and mismatch distribution analyses supported a demographic expansion of D. maruadsi in between last Pleistocene to early Holocene period which influenced present day distribution pattern. Contemporary factors such as oceanic currents and different life history traits are also believed to play significant roles in the observed population structure and biogeographical pattern. Based on these results, recommendations on how stocks of the Japanese scad should be managed are offered.

摘要

日本海豹（Decapterus maruadsi）（Carangidae）是亚洲经济上重要的海洋物种，但其开发显示出过度捕捞的迹象。为了证明其种群结构，使用线粒体细胞色素b基因对来自印度西部西太平洋区域中部的该物种的几个种群进行了种群遗传和系统地理学研究。桑达兰地区人口（包括罗萨里奥（菲律宾）和拉廊（安达曼海））的遗传同质性具有较低的核苷酸多样性（π  = 0.001–0.003）但具有较高的单倍型多样性（h = 0.503–0.822）。相比之下，F _ST，AMOVA和SAMOVA揭示了这一群体与越南北部人口之间的遗传结构清晰，而越南中部的庆和人口则是两个不同区域人口之间的混合群体。中立和不匹配分布分析支持D. maruadsi的人口扩展在最后更新世至全新世早期之间，影响了当今的分布格局。人们还认为，诸如洋流和不同生活史特征等当代因素在观察到的人口结构和生物地理格局中也起着重要作用。根据这些结果，提出了有关如何管理日本学术库存的建议。