194 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Figure 9.- Scale from a mal< 



shad that was probably 2 years old. This Ogure illustrates the appearanc 



scale. 



>f a regenerate 



well as complete grooves (extending unbroken 

 from one edge to the other). Figure 8 illustrates 

 this procedure of counting by numbering the 

 I ransverse grooves 1, 2, 3, and so on, starting with 

 the first transverse groove above the baseline. 

 Since it is impossible to obtain photographs of 

 shad scales with all details clearly shown, the dia- 

 grammatic overlay of figure 8 was prepared to 

 help illustrate the items discussed. These are 

 seen while actually reading the scales by changing 

 the focus of the microscope to bring out each 

 detail. The scale in this figure is from a 4-year- 

 old female taken during its first spawning migra- 

 tion. On this scale there are 8 transverse grooves 

 lying within the fresh-water zone. 5 within the 

 first annulus, 10 within the second annulus, and L4 

 within the third annulus. 



The transverse-groove counts made on the 164 

 scales are shown in table 1. The number of trans- 

 verse grooves lying within the fresh-water zone of 

 the scale ranges from 1 to 5. but is usually 2 or -'!. 

 The number entering the area enclosed by the first 

 annulus ranges from 4 to 7. but is usually 5 or (i. 

 Within the second annulus, counts of 9 and In 

 transverse grooves predominate, but the range is 

 from 8 to 11. The number entering the area en- 

 closed by the third annulus is generally 13 or 14, 

 with a range from 12 to 16. On a few fish which 

 had not spawned until they were ."> years old or 

 older, it was found that lti to 18 transverse grooves 

 came into the area enclosed by the fourth annulus; 

 but, because of the confusion of lines caused by the 

 scarred area in the central anterior portion of most 

 scales, it was found to be of value to use groove 



