AGE DETERMINATION FROM SCALES OF LAKE TROUT 



TWO RIVERS 

 MANITOWOC 



SHEBOYGAN 



BETSIE PT 



ARCADIA 



RACINE 



Scale of miles 



Figure 2. — Southern Lake Michigan showing points of 

 capture of lake trout having deformed or missing fins. 

 Year class indicated by fin mark is as follows: 1944, 

 squares; 1945, circles; 1946, triangles. The sizes of the 

 symbols indicate numbers of fish captured at the var- 

 ious points, the smaller size of each symbol represents 

 1-4 fish, the larger one represents 5-9 fish. 



ration of fin-clipped fish from those with deform- 

 ed fins. Small lake trout with abnormalities re- 

 sulting from causes other than clipping undoubt- 

 edly were included. 



PREPARATION AND EXAMINATION OF SCALES 



The scales were made ready for examination 

 by preparing impressions in plastic. Washed 



scales were mounted, still damp, on 3- by 5-inch 

 cards of gummed Kraft paper. Scale samples 

 from 9 to 30 fish were mounted on each card in 

 2 or 3 rows depending on the size of the scales 

 and the number per sample to be mounted. 

 Three to 6 symmetrical scales from each fish 

 were mounted; usually at least one scale was 

 mounted with the smooth or inner surface up, as 

 the annuli often were prominent on that side 



FuuRE 3. — Map of Lake Michigan showing boundaries 

 of the statistical areas or districts 1-8, and of sectional 

 maps in figures 1 and 2. 



