Stock structure of Japanese anchovy

1.繁殖生态学进行了比较4个亚种群，居住在日本。在相模湾、若狭湾和大坂湾的沿岸沃茨，产卵活动普遍受到水温高于15℃的控制。在此温度范围内，产卵期因地区而异，这取决于反映食物供应的营养条件。三个海湾之间的成熟体长不同。本州东部近海的白鲳在远低于15℃的温度环境下产卵。此外，近海鱼的成熟体长为10 cm，比沿海鱼晚。各地点的产卵量和产卵频率与温度呈正相关。但在较低温度环境下，本州以东近海的鱼表现出与沿岸鱼相当的产卵能力。不同地点的鳀鱼根据其所处的环境表现出不同的产卵模式.用扫描电子显微镜对九州至北海道的6个地点的耳石进行了显微观察。从孵化到60日龄的日生长轮所确定的早期生长在不同的采样点之间是不同的。增长率呈南部高、北部低的趋势。此外，外部形态进行了检查，测量了12个身体部位。随着地理距离的增加，形态变异有增加的趋势。这表明存在不同孵化和分布区域的地方种群。本文比较了日本海若狭湾和日本本州东太平洋沿岸沉积物中δ ~（15）-N、δ ~（13）-C的稳定同位素比值。δ-15-N和δ-13-C的值在两个区域之间总体上存在差异，但它们在样本之间有很大的重叠和差异。这种巨大的变异似乎使稳定同位素比值难以用于种群鉴定。

1. Reproductive ecology was compared between 4 sub-populations that inhabit off Japan. The spawning activity was commonly controlled by the water temperature higher than 15℃ for anchovies in the coastal waters in Sagami Bay, Wakasa Bay and Osaka Bay. Within this temperature range the spawning period was varied between localities depending on nutritional conditions reflecting food availability. Maturity body lengths differed among the three bays. The anchovy in the offshore east of Honshu spawned under the temperature environment much lower than 15℃. Moreover, the offshore anchovy matured at 10cm in body length, later than that for the coastal anchovy. Fecundity and spawning frequency were positively correlated with temperature for anchovies in every locality. However, the anchovy offshore east of Honshu showed spawning ability equivalent to the coastal anchovy in the lower temperature environment. Anchovies in the different localities exhibited different spawning patterns in accordance with their environment.2. Otolith microstructure was examined with a scanning electron microscope for 6 sites samples from Kyushu to Hokkaido. The early stage growth determined by daily growth rings from hatching to 60 days was different among the sampling sites. The growth rate tended to be higher in the south and lower in the north. In addition, external morphology was examined with 12 body parts measured. The morphological variation tended to increase with geographical distance. This suggests the existence of local populations that have different hatching and distribution areas.3. Stable isotope ratios of delta-15-N delta 13-C was compared between anchovies from Wakasa Bay, Japan Sea and off the Pacific coast of eastern Honshu. The values of delta-15-N and delta-13-C ranged differently between two areas as a whole, though they overlapped and varied among samples considerably. The great variation seemed to make the use of the stable isotope ratio difficult for stock identification.