papers on biology and agriculture s9 



THE DETERMINATION OF THE AGE OF FISHES 

 FROM SCALE CHARACTERISTICS 



Frank Smith, University of Illinois 



Most people will be interested in the statement that 

 many of our common kinds of fish carry about with them 

 a record of the number of winters which they may have 

 passed, and that the record is accessible to anyone who 

 is familiar with the code, and who will take scales from 

 a suitable place on the body of the fish and examine them 

 with a microscope of rather low power. There is much 

 difference in the ease and certainty with which such rec- 

 ords can be deciphered, but among some groups, includ- 

 ing sunfishes, black bass, and allied kinds, age determina- 

 tion is accomplished quite easily. 



The presence of "winter marks" or annuli on scales 

 of certain kinds of fish has been known for many years 

 to specialists, and there is already an extensive litera- 

 ture dealing with age determination of marine and fresh- 

 water fishes of Europe, and a few papers have appeared 

 dealing with age studies of certain marine fishes of North 

 America. Last year four papers from the University of 

 Toronto dealt with rates of growth of Lake Erie fishes, 

 including ciscoes, wall-eyed pike, yellow perch, and white- 

 fish; and within the past few weeks a paper has been pub- 

 lished by the Bureau of Fisheries at Washington which 

 contains the results of similar studies on the orange- 

 spotted sunfish which is a small form, common in Illi- 

 nois and in various parts of the Mississippi Valley. This 

 last paper is sold by the Superintendent of Documents, 

 Washington, D. C, and is designated as : Bureau of Fish- 

 eries Document No. 938. It contains illustrations show- 

 ing the appearance of scales and the annuli or winter 

 marks when examined with the microscope. 



It seems almost surprising that so little attention has 

 been given thus far to such studies on fishes of the Mis- 

 sissippi Valley and of Illinois, but a beginning has been 

 made and much greater interest doubtless will be evi- 

 dent in the near future. An extensive series of studies 

 on Michigan fishes by zoologists of the University of 

 Michigan is now in progress, and a beginning has been 



