大黄鱼Pseudosciaena crocea(Richardson)耳石的轮纹形成周期及其年龄鉴定问题

为了满足渔业经济不断增长的需要，就必须对鱼类，特别是重要经济种类的生活习性进行系统的深入研究。因此，确定鱼类年龄鉴定的方法，从而依据年龄的鉴定，按不同生命阶段来研究鱼类的生活规律，就成为最基本的问题了。关于大黄鱼的年龄鉴定问题，尚未见有专门进行研究的报导。在支献记载上，福建水产研究所和广东水产研究所曾先后用耳石和鳞片估计大黄鱼的年龄，但并未对年龄鉴定的依据与方法进行分析。Irie 则对黄花鱼属的耳石轮纹形成周期问题进行了一些观察。为了探讨大黄鱼年龄鉴定的确切方法，自1958年秋季起，我们展开了这方面的工作，系统地逐月搜集了大黄鱼耳石、鳞片、脊椎骨等项可能供作鉴别年龄的材料。观察结果以耳石上显示的轮纹最为清晰而有规律，因此，我们选用耳石作为鉴定大黄鱼年龄的研究对象。本文着重以浙江舟山及其邻近海区的材料为主，对大黄鱼耳石轮纹形成周期、轮纹性状以及鉴别年轮的主要标志等加以分析与讨论。此外，对于春、秋宗幼鱼第一个年轮的形成时期与鉴定方法也进行了探讨。在我们所研究的材料中，1957年5月份的部分耳石是浙江温州水产局供给的；1960年5-7月份的部分幼鱼耳石是浙江省渔业资源调查委员会所借给；未观察耳石年龄的幼鱼长度组成的季节变化资料则是沙学绅和杨纪明同志供给的。中国科学院地质古生物研究所曾协助我们设计了耳石磨片机，均此志谢。除作者等外，全部耳石磨片工作是滕文法同志担任的，黄颂芳同志参加了资料的统计，林汝范同志协助了资料的搜集工作。本文承张孝威教授热情指导，作者谨致谢忱。

THE CYCLE OF RING-FORMATION ON THE OTOLITH OF THE LARGE YELLOW CROAKER, PSEUDOSCIAENA CROCEA (RICHARDSON), WITH SPECIAL REFERENCE TO AGE-DETERMINATION

The otoliths from 3789 individuals, taken monthly from the Chekiang coast, during the period from September 1958 to December 1959 inclusive, were used in the present investigation.Monthly observation on the marginal structure of the otoliths and terminal index of ,each ring group carried out over a period of one year confirmed that the rings on the otolith were formed annually (excluding the first ring of the autumn spawners), as there was an complete turning over of one sort margin to the other during a definite period of the year. It is therefore concluded that the otolith of the Large Yellow Croaker is a reliable index for age determination.The opaque zone at the margin began to appear in January. Its percentage occurrance was highest in May and June, and fell to zero in July. However, the period of commencement of formation of the opaque zone varied regularly according to the age of the fish. It began to appear in April in the individuals with 1-13 rings, in February and March in those with 14-17 rings, and as early as in January in those with 18 rings onward.A preliminary analysis of the monthly length frequency distribution of the young fish and of the marginal structure of the otoliths revealed that the first annual ring on the otoliths of the young fish of the spring spawners was formed one year after and that of the young fish of the autumn spawners a year and a half after being laid.During the winter and spring the growth of the otolith was very slow, but during the summer and autumn it showed remarkable growth. It can be deduced that the growth rate of the present species also varies periodically, i.e. it grows slowly in the earlier half of the year, and remarkably in the latter half of the year.In the present report, the distinction between the true annulus and the false annulus has also been described.