To clarify the survival process of walleye pollock larvae of the Japan Pacific stock in relation to the individual egg size, we estimated the original relative egg diameter from the diameter of the hatch check formed on larval sagittal otoliths. Significant positive correlations were obtained between egg diameter and embryonic body length, yolk sac volume, and lapillar otolith diameter in 3-year groups (2013–2015 year classes) collected with a plankton net in Funka Bay. Embryos before hatching were without a check; however, checks were observed on all larval otoliths just after hatching. The check diameters showed significant positive regressions to age at collection (days after hatching) in 2014 and 2015 year classes, however not in the 2013 year class. Diameters of eggs collected with a ring net in Funka Bay gradually increased from 2013 to 2015 year classes. During the 2013–2015 spawning seasons, the proportion of adult females of the 2007 and 2009 year classes, which had relatively high abundances, gradually increased to higher proportions with age (43%, 57%, and <73%, respectively), indicating that the mechanism by which the eggs gradually became larger. The low water temperature experienced by the spawners ca. 2 months earlier, advancement in spawner age, and increase of repeat spawners (at least twice in their life time) would contribute to the increase in egg size and growth and survival rate of walleye pollock larvae.

中文翻译：

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卵大小对野生大眼鳕Gadus chalcogrammus 幼虫生长速度和成活率的影响

为了阐明日本太平洋种群的狭鳕幼虫的生存过程与个体卵大小的关系，我们根据幼虫矢状耳石上形成的孵化检查直径估计了原始相对卵直径。在芬卡湾用浮游生物网收集的 3 年组（2013-2015 年班）中，卵子直径与胚胎体长、卵黄囊体积和耳石直径之间存在显着的正相关。孵化前的胚胎未经检查；然而，在孵化后对所有幼虫耳石进行了检查。检查直径在 2014 年和 2015 年班级中显示出对收集年龄（孵化后天数）的显着正回归，但在 2013 年班级中没有。从 2013 年到 2015 年年级，在 Funka 湾用环网收集的鸡蛋直径逐渐增加。在 2013-2015 产卵季节，丰度相对较高的 2007 年和 2009 年级成年雌性的比例随着年龄的增长逐渐增加至更高的比例（分别为 43%、57% 和 <73%），表明卵逐渐变大的机制。产卵者大约经历的低水温。2 个月前，产卵者年龄的提高和重复产卵者的增加（在它们的一生中至少两次）将有助于增加卵的大小以及鳕鱼幼虫的生长和存活率。随着年龄的增长逐渐增加到更高的比例（分别为43％，57％和<73％），表明鸡蛋逐渐变大的机制。产卵者大约经历的低水温。2 个月前，产卵者年龄的提高和重复产卵者的增加（在它们的一生中至少两次）将有助于增加卵的大小以及鳕鱼幼虫的生长和存活率。随着年龄的增长逐渐增加到更高的比例（分别为43％，57％和<73％），表明鸡蛋逐渐变大的机制。产卵者大约经历的低水温。2 个月前，产卵者年龄的提高和重复产卵者的增加（在它们的一生中至少两次）将有助于增加卵的大小以及鳕鱼幼虫的生长和存活率。