Annulus Formation in Scales of the Common Shiner, Notropis cornutus chrysocephalus (Rafinesque)

Abstract

S INCE Hoffbauer (1898-1900) observed in the scales of the carp concentric rings which he supposed to be growth rings, the technique of determining the age of fishes by counting the annuli has been used extensively. Many complications arise, however. For example, Blair (1937) described a definite but rather difficult distinction between winter marks and spawning marks in salmon scales. Hansen (1936) has shown that the annulus of the white crappie scale does not form in the winter but in early summer. Such complications have led to uncertainty regarding the application of the age determination technique. A study of the interpretation of the scales in relation to life history is therefore necessary for each type fish before its age may be determined from scale markings. From this standpoint such a study was undertaken on the scales of Notropis cornutus chrysocephalus (Rafinesque). The author is grateful to Dr. John W. Price and Mr. E. N. Warner, both of the Department of Zoology and Entomology, Ohio State University, for advice and photographic work respectively. The Ohio Division of Conservation, through its representative, Mr. E. L. Wickliff, very kindly furnished the material and related data.