AGE DETERMIXATIOX FROM SCALES OF LAKE TROUT 



19 



Fif.iRE 11. — Scale of a lake trout 15.1 inches long, marked in September 1945 and recovered April 25, 1950. The focus 

 of this scale is located anteriorly. The annuli are indistinct. Such a scale is difficult to read. The band of new 

 growth is narrow. 



TIME OF ANNULUS FORMATION 



New gi'owth on lake trout scales is first seen as a 

 narrow, clear band outside a darker band of the 

 closely spaced circuli of "winter growth." In 

 the early part of the season, new growth is too 

 narrow to be distinguished from spacing between 

 winter circtili. For this reason, new growth was 

 i(h'iitified and measured only when it had attained 

 a width greater than that of the spacing between 

 |)rece(Hng circuli and an outer circulus had formed 



at least part way around the scale. Hence, in 

 this study, the scales had grown an undetermined, 

 though short, time before growth was recorded. 

 One lake trout had some new growth on its scales 

 -laiuiary 19, but no others appeared with new 

 growth until the latter part of .\Iarch. Similarly, 

 a single specimen without new growth was caught 

 September 23, more than a month after new 

 growth was started on the scales of all other fish 

 in the sample. The two aberrant specimens are 



