Functional stock structure related to spawning of the Japanese flounder in the Sea of Japan

牙鲆(Paralichthys Olivaceus)是一种重要的近海鱼类，广泛分布于西北太平洋沿岸海域。当我们考虑渔业管理和种群增加时，最重要的因素似乎是理解作为产卵单位的种群结构。本研究对采自日本沿海地区的比目鱼幼鱼的形态、生态和生理特性进行了地理变异研究，并对其遗传群体结构进行了分析。结果如下：1.背鳍和肛鳍鳍数的地理变异明显：北低南高，不连续地被北半岛隔开。2.实验证实，变态开始时的温度升高会增加牙槽的长度。由于野生幼体在海洋中所处的平均水温在北部略高，上述地理差异似乎有遗传背景。幼鱼的日生长在北部高于南方。在包括太平洋在内的几乎整个沿海地区采集的幼鱼中，mt-DNA控制区的核苷酸序列差异很大。5.识别出两种主要单倍型，这两种类型在大多数采样点中的比例没有显著差异，但佐渡ISL的比例出现了倾斜。6.对和歌湾地区采集的约200只成虫的单倍型组成进行了分析，发现部分种群在产卵过程中会向西迁移。这些结果表明，幼虫的迁移和成体的迁徙通常会发生频繁的基因流动，但日本海沿岸可能存在不同的产卵种群，具有不同的生态生理和形态特征。

The Japanese flounder (Paralichthys olivaceus) is one of the most important coastal fishes, commonly distributed in coastal waters of the northwestern Pacific. When we consider fisheries management and stock enhancemnet, the most important factor appears to understaned stock structure which works as a spawning unit. In the present study, we examined geographical variations in morphological, ecological and physiological characterisitcs and analyzed genetic stock structure of juvenile flounder which were collected from the entire area along the coast of the Japan Sea.The results obtained are as follows.1.Geographical variations in unmber of dorsal and anal fin rays were clear : lower in north and higher in south, and discontinuously separated by the Noto peninsula.2.It was experimentaly confirmed that higher temperature at onset of metamorphosis increased the unbmer. Since average water temperature to which the wild larvae encountered in the sea is slightly higher in north, the above mentioned geographical variation seems to have a genetic background.Daily growth of juveniles was higher in north than in south.Nusleotide sequence in control region of mt-DNA was highly variable among juveniles collected from almost whole coastal area inclucing the Pacific.5.Two major haplotypes were recognized, and proportion of the 2 types was not significantly different among most of sampling sites, however a skewed proportion was observed in Sado Isl. and Hokkaido.6.The haplotype composition of about 200 adults collected in the Wakasa Bay area was examined to see difference by age and season, showing that a part of the population would move toward west from this area in relation to spawning.These results suggest that a frequent gene flow commonly occur by larval transport and adult migration, but there may be different spawning stocks having different eco-physiological and morphological features along the coast of the Japan Sea.