FISHERY BULLETIN: VOL. 85, NO. 4 



ful where assigned components of variation can 

 be maximized relative to unassigned components. 

 I compared indices of variation assignable to mea- 

 surement size (standard specimens), geographic, 

 and sexual causes in the 18 characters by means 

 of the alternate standard deviation (see Methods). 

 First, I investigated relationships between varia- 

 tion and the size of a character. When mean re- 

 sponses for measurements in standard-sized fish 

 from the Kodiak region were used as a basis of 

 comparison, variability was positively related to 

 size of the character, with the two variates signif- 

 icantly correlated (Fig. 4). 



Size accounted for about 62% iR'^) of the varia- 

 tion between characters. To remove its effect in 

 further comparisons, I used an alternate version 

 of the coefficient of variation; i.e., the alternate 

 standard deviation for each character divided by 

 a size index (Kodiak) for that character xlOO. 

 Although the alternate coefficient of variation re- 

 duced the unassigned variability, some sizable 

 differences remained between characters (Table 

 3) — major dimensions of the head and dorsum 

 varied least, fin spines and small features of the 

 head varied most, and the symphyseal knob 

 varied considerably more than any other charac- 

 ter. With the exception of belly, the major trunk 



Table 3. — Evidence for unassigned variation in measurements in 

 Pacific ocean percfi after correction for measurement size. Mea- 

 surements (Y) are related to a standard-sized fish of 260 mm SL 

 from the Kodiak region by regressions in Table 2. Relative variation 

 for each measurement is indexed by the alternate coefficient of 

 variation (ACV) (see text) pooled over all regions and expressed as 

 a percentage. Measurements arranged by increasing alternate co- 

 efficient of variation in the last column. 



5.0 



4.0 



Y=1 . 1126 + 0. 0246X 

 N = 18, r = 0.787* • 



> 



111 

 Q 



Q 



ir 

 < 



Q 



3.0 



2.0 - 



• • 



w 



1.0- 



_L 



_L 



J_ 



P<0.01 



J_ 



_L 



_L 



10 20 30 40 50 60 70 80 90 100 110 120 

 AVERAGE SIZE OF MEASUREMENT 



Figure 4. — Relationship between absolute size and variability of measurements in 

 Pacific ocean perch. Character sizes are mean responses for hypothetical 260 mm 

 SL fish from the Kodiak region as estimated from the regressions of Table 2; 

 variability is estimated by alternate standard deviations for each character (see 

 Methods) pooled over all regions. 



676 



