336 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



annulus i 



^*C&.£r*v? 



Figure 22. 



-Scale from a 2-year-old grayling (total length 9.2 ins.) captured June 10, 1954. 



for the present year. 



Annulus has been completed 



Two-year-old grayling averaged very little 

 earlier than yearlings as to time of annulus for- 

 mation. All thirteen 2 -year-olds collected be- 

 tween June 10 and 26, 1954, had a complete 

 annulus for the current year. The first fish taken, 

 June 10, had already added 4 to 6 new circuli 

 beyond the second year mark. 



Three-year-old grayling had a different growth 

 pattern from younger ones. The fish of age-group 

 III reported on here were trapped during their 

 first spawning migration. No scales from 3-year- 

 olds less than 13 inches in total length had an 

 evident annulus during the current year. How- 

 ever, some fish longer than 13 inches showed a 

 sub-marginal third-year mark. Consequently, 1 

 year was added empirically to the age of all fish 

 3 years old and older, when the expected year 

 mark was not evident at or near the scale margin. 



Growth subsequent to the thud annulus was 

 small and slow in both body and scale lengths- 

 In age-group III during the remainder of the 1954 

 season, I found individuals in the last week of 

 July that appeared to have just completed their 

 third annulus. By the end of the first week of 

 August, all specimens clearly of this age-group 

 that were studied had deposited only one to three 

 new circuli beyond the year mark. In years of 

 life after the fourth, growth continued slow or 

 ceased altogether, making further annulus recog- 

 nition impossible. 



Failure of first annulus to appear 



A second problem in the age assessment of 

 grayling scales was the apparent failure of annulus 

 I to appear in certain fish and in certain years. 

 The year 1953 was such a year in Grebe Lake, 



