Ocean Research Institute, University of Tokyo, Nakano, Tokyo 164-8639, Japan.
J Fish Biol. 2009 Jun;74(9):1915-33. doi: 10.1111/j.1095-8649.2009.02287.x.
The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30 degrees C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25 degrees C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20-30 degrees C or after 20 days at 15 degrees C, but no feeding occurred at 5 and 10 degrees C. No otolith growth occurred at 5 and 10 degrees C except in two individuals with minimal increment deposition at 10 degrees C. Otolith growth was proportional to water temperature within 15-25 degrees C and not different between 25 and 30 degrees C. At 15, 25 and 30 degrees C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0.00-0.01 day(-1) at 5 and 10 degrees C, 0.43-0.48 day(-1) at 15 degrees C and 0.94-1.07 day(-1) at 20-30 degrees C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at < or =10 degrees C under experimental conditions. Hence, future studies analysing the otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.
采用 ALC 对玻璃鳗和幼鳗的耳石进行标记后，研究了水温及摄食状态对其生长的影响。在盐度 32 的条件下，将个体分别饲养在 5、10、15、20、25 和 30℃，并分为摄食和不摄食两组。为了消除用光镜（OM）或扫描电镜（SEM）观察耳石边缘的困难，在实验过程中，每隔 10 天从每个水槽中抽取 3-10 尾个体，在标记第二次耳石后，继续在 25℃下饲养 10 天。使用 OM 和 SEM 测量耳石生长和日轮数。在 20-30℃下，大多数个体在 10 天后开始摄食，在 15℃下则需 20 天，而在 5 和 10℃下不摄食。在 5 和 10℃下，除了有两个个体在 10℃时仅最小程度地沉积日轮外，没有耳石生长。在 15-25℃范围内，耳石生长与水温成正比，而在 25-30℃范围内，两者没有差异。在 15、25 和 30℃下，摄食条件下的平均耳石生长速度高于不摄食条件。水温间的日轮数存在显著差异（5 和 10℃时为 0.00-0.01 天-1，15℃时为 0.43-0.48 天-1，20-30℃时为 0.94-1.07 天-1）。结果表明，在实验条件下，水温<或=10℃时，玻璃鳗和幼鳗的耳石生长停止。因此，未来分析野生日本鳗玻璃鳗和幼鳗耳石的研究需要仔细考虑幼鱼在野外可能经历的水温。
