ABSTRACT: Aging Antarctic icefish is difficult because of their lack of scales and poorly calcified bones. Icefish ages must therefore be estimated from otoliths. We describe a method of reading daily micro-increments in connection with shape, size and mass analyses of the otoliths of the South Georgia icefish Pseudochaenichthys georgianus. Changes in otolith morphology and mass correlate with fish size and age group. The otolith micro-increment analysis is capable of establishing the age of an icefish by relating the daily micro-increment count to the life history of the fish. Micro-increment measurements and analyses are relatively simple to do by light and scanning electron microscopy and by using micro-densitometer and digitizing equipment. Drastic changes in the life history of an individual are reflected by measurable changes in its otolith micro-increment data as seen in our analyses of age groups 0-VI. The initial drastic change in daily micro-increment shapes and periodicities occur in connection with the hatching period of the icefish. The next drastic change in otolith shape and daily micro-increments occurs when ~7 cm long fish shift from pelagic to benthic habitats. As the fish age beyond group III, individual otolith variability lessens until they begin spawning. Our results indicate a single population of P. georgianus between the Antarctic Peninsula and South Georgia.

中文翻译：

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基于耳石的多种方法确定冰鱼Pseudochaenichthys georgianus（Channichthyidae）的年龄

摘要：由于缺乏鳞片和骨骼钙化，南极冰鱼很难老化。因此，必须根据耳石估计冰鱼的年龄。我们描述了一种与形状，大小和质量分析有关的佐治亚州南部冰鱼Pseudochaenichthys georgianus的耳石的形状，大小和质量的每日微增量读数方法。耳石形态和质量的变化与鱼类的大小和年龄组相关。耳石微增量分析能够通过将每日微增量计数与鱼的生活史相关联来确定冰鱼的年龄。通过光和扫描电子显微镜以及使用微密度计和数字化设备，微增量测量和分析相对简单。如我们对0-VI年龄组的分析所见，个体的耳石微增量数据的可测量变化反映了一个人的生活史上的巨大变化。每日微增量形状和周期性的初始急剧变化与冰鱼的孵化期有关。当约7厘米长的鱼类从中上层生境转变为底栖生境时，耳石的形状和下一个每天的微小增量都会发生下一个急剧变化。随着鱼类年龄超过第三组，个体的耳石变异性会降低，直到它们开始产卵为止。我们的结果表明，南极半岛和南乔治亚之间的P. Georgianus。