NORTH AMERICAN SALMONIDAE 



257 



-OOnSAL TO LATERAL UWE 



- vENTRAk TO LATERAL LINE 



- 10-10 RCRCEMTiLE RAW«E 



- STAXOAOO DCV>ATO>t 



TSHAWYTSCHA 



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^ — o---- 



AVERAGE HORIZONTAL SCALE ROWS 



Figure 9. — Number of horizontal scale rows. 



The average horizontal scale counts for Onfor- 

 hywhu.s, two species of Salreliniw, and Salnio 

 gairdneri are shown in figure 9. Mahnn has the 

 largest number, followed by alptnm and gor- 

 husclia. The variation in number of scales within 

 species is lai'ge, tlie maximum between means for 

 gorhiischa being 3.3 in the number of scale rows 

 above the lateral line. 



Despite large ditierences in the sample means a 

 definite trend exists m Oncorhynchus from the 

 fine-scaled gorhuscha to the relatively coaree- 

 scaled keta and nerka. 



ANALYSIS OF MERISTIC CHARACTERS 



All meristic charactere were placed on a common 

 basis to facilitate their comparison. Such a basis 

 was established by determining the lowest and 

 liighest species means for any given character and 

 tiien using the numerical diHerence between the 

 two means as a yardstick. The lowest mean lias 

 been rated as 0, the highest as 10, and tlie inter- 

 mediate means have been rated in between accord- 

 ing to their position on the scale. The ranking of 

 charactei-s is given by species in table 26. 



As explained earlier, not all of tliese ciiaracters 

 are independent variables. Therefore, if we use 

 two closely con-elated characters in attempting to 

 weigli differences between species from several 

 charactei-s, we are in effect giving double weight 



to the same measure. Figures 10 to 12 show the 

 close correlation between three pairs of charactei-s. 

 To obtain a joint ranking of these pairs of cor- 

 related characters, the rankings were adjusted 

 (table 27) according to a correction factor (table 

 26) to equalize the average ranking for the species 

 with available data. After obtaining the joint 

 rankings for three pairs of correlated meristic 

 characters, we are left with six presumably inde- 

 pendent meristic rankings, which are listed by 

 species in table 28. 





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 o 



<D 



Z 



^ 40 



z 

 < 

 a: 





2 4 6 8 l( 



RANKING OF DORSAL FIN RAYS 



Figure 10. — Relation between dorsal and anal fin rays. 



Ul 8 



o 



e> 



z 



Z 



2 2 



20 40 60 80 100 



RANKING OF VERTEBRAE 



Figure 11. — Relation between vertebrae and lateral-line 

 scales. 



