198 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



* 





Figure 12. 



-Scale from a 6-year-old female shad measuring 19.1 inches. The fish was taken at the mouth of the 

 Connecticut River mi its way to spawn for the first time. 



APPLICATION OF CRITERIA 



The criteria, as described, were applied to the 

 scales on which poor agreement was reached, and 

 little difficulty was experienced in determining 

 the location of the first, second, and third annuli. 

 Once the location of an annulus was determined 

 by groove count, the annulus usually could be 

 traced from the anterior sculptured area into the 

 posterior area of the scale even though obscured 

 and confused by false annuli. Usually the true 

 annuli were represented by more heavily defined 

 ridges in the posterior section than the Palse 

 annuli. 



The fourth, fifth, and sixth annuli were usually 

 clearly visible and proportionately spaced on 

 scales of fish which had not previously spawned; 

 hence, by using transverse-groove counts to locate 

 the first, second, and third annuli and then count- 

 ing each annulus past the third one, it was possible 

 to determine the age of shad which had not previ- 

 ously spawned. 



Proficiency in interpreting the age of any spe- 

 cies of fish from scales requires practice. This is 

 especially true when working with scales as diffi- 

 cult to read as the shad's; however, it is believed 

 that by applying the criteria presented here, any- 



