FISHERY BULLETIN: VOL. 71, NO. 2 



but intermediate compared to Naknek Lake 

 and Chignik Lake populations. Our counts, as 

 well as those on Lake McDonald fish, do not 

 support McCart's contention that the low- 

 rakered form persisted in the vicinity of the 

 Columbia River Basin during the Pleistocene 

 glaciation. 



Vertebrae 



As with other meristic characters, the verte- 

 bral count of the pygmy whitefish is low for a 

 coregonine. The number of vertebrae is variable 

 however — from 49 to 55. The plasticity of this 

 character is within individual populations as 

 the species exhibits similarity in the mean 

 count of vertebrae throughout its range. The 

 Flathead Lake fish have a mean number of 52.3 

 and the Bull Lake specimens, a mean of 52.7 

 (Table 3). Mean vertebral count of the fish from 

 Lake Superior was given as 52.9 by Eschmeyer 

 and Bailey (1955). The lowest mean is 51.5 

 for Chignik Lake (McCart, 1970). 



It appears that most of the variation in the 

 vertebral number is in the caudal rather than 

 precaudal vertebrae. The number of caudal 

 vertebrae ranges from 21 to 26 whereas the 

 precaudals vary from 27 to 31 in Flathead Lake 

 and Bull Lake fish. The number of caudals 

 individually plotted with their respective total 

 number have means that nearly increase by the 

 value of one with each increase in similar value 

 in total number of vertebrae (Table 4). 



Although low, the total number of vertebrae 

 of the pygmy whitefish overlaps the lower 

 range of the mountain whitefish. Holt (1960) 

 gave a range of 53 to 61 for the mountain 

 whitefish in the Columbia River drainage. 

 Twenty specimens of the mountain whitefish 



Table 3. — Frequency distribution of total number of 

 vertebrae in pygmy whitefish. 



Table 4. — Relation of number of caudal vertebrae to 

 total number of vertebrae in pygmy whitefish. 



from Lolo Creek used in our study had caudal 

 vertebrae ranging from 25 to 27, again a slight 

 overlap. 



AGE AND GROWTH 



Age was determined for 494 pygmy whitefish 

 taken from Flathead Lake during April 1967 

 through May 1971. Sex was determined on 

 272 specimens, mostly from mature fish cap- 

 tured in November and December. 



Only one fish of age was collected. Fish 

 of this age are so small that they are unlikely 

 to be captured in the collecting gear we used. 

 The percentage of the total fish by age group 

 was: 0,0.2% ; L47.2% ; 11,46.1% ; in,5.9% ; and 

 IV, 0.6% . Overlap was considerable in the 

 length-frequency distribution between adjacent 

 age groups and between the sexes (Table 5). 



Growth rate was calculated by establishing 

 the relationship between the body length and 

 the anterior scale radius. The value of 0.9854, 

 the coefficient of variation r, developed on the 

 493 measurements, suggests a strong degree 

 of linearity between the body-scale measure- 

 ments. This linearity differs from the sigmoid 

 body-scale relationship found for pygmy white- 

 fish from Alaskan waters by Heard and Hartman 

 (1966). 



The equation fitted from the individual pairs 

 of body and scale measurements was: Total 

 body length = 0.913 anterior scale radius + 

 61.63. Mean body lengths from each scale 

 radius were plotted against the calculated re- 

 gression line shown in Figure 1. Total lengths 

 were back calculated by direct proportion 

 (Table 6). 



Annual growth of females in Flathead Lake 

 exceeded growth reported for Brooks Lake 

 (Alaska), Lake McDonald (Montana), and Lake 



590 



