Robertson (19h7) reported that 63 specimens of Salmo clarki lewisi 

 from Upper No Name Lake in Uyomine; exhibited variations in standard 

 length — total length relati'-nship according to size of fish„ Five-inch 

 fish had a factor of 0.826 (total length to stan-lard length) , while 20- 

 inch fish had a factor of 0.877. The mean figure for the 63 fish was 

 0.863. 



The present Yellowstone data have not been analyzed with respect to 

 size of fish in relation to conversion factors. Table 1 is restricted to 

 sizes of black-spotted trout from 2Ul millimeters (9.5 inches) total length 

 to U53 millimeters (17.8 inches). Conversion factors as reported by- 

 Robertson would range from approximately O.861 to C.87i; for fish of these 

 siyes. These values cause a difference of no more than two millimeters nn 

 the converted length when applied to fish vdthin this sizs range. Factors 

 listed in Table 2 are presented for use over the entire range from 2Ul to 

 ii53 millimeters ^^dth the qualification that measurements on fish at the 

 extremesof the range may be as much as two millimeters in error after the 

 conversion. 



Robertson's conversion factor^ O.863. corresponds with the factor, 

 0,8725, for Yellowstone Lake fish. A fish of 350 millimeters total length 

 would be 302.05 millimeters in standard length according to the Robertson 

 factor^ and 305.38 with the Yellowstone factor. 



Fleener (1952) reported conversion factors-, 1,1950 (standard length to 

 total length) and 0,8367 (total length to standard length), for 305 cut- 

 throat trout in Logan River ^ Utah. Fish on which these factors are based 

 measured from IiO to 290 millimeters in total length. These factors, based 

 on both sexes, differ somewhat from the Yellowstone and Robertson factors. 

 This is to be expected, since the Logan River fish were considerably smaller 

 than those used in the other two studies. The occurrence of a proportional 

 decrease in caudal fin size with increase in length of fish suggests agree- 

 ment with the observations of Carlander and Smith, of Robertson, and of Hile. 

 Another possible reason for the difference between the Logan River and the 

 Yellowstone factors lies in the fact that the quality of Logan River stock 

 is not known. There has been ample opportunity for hybridization between 

 species and between subspecies in this stream^ and it is not certain that 

 cutthroat of Yellowstone origin only have been introduced in the many cut- 

 throat plantings that have taken place here. 



Factors pertaining to males do not bear a consistent relationship to 

 factors relating to females in these Yellowstone data. Table 2 shows,, for 

 example, that, for males conversion from standard to fork and to total 

 length, the factors ai-e greater than for females. Conversion from fork 

 length to total length, however, shows the factor for females to be higher 

 than that for males. It is possible for tnis relationship to exist but 

 nrobably the real reason for this discrepancy lies in the fact that dif- 

 ferent populations of fish were used for the measurements. Factors relat- 

 ing fork and total length wore derived from Arnica Creek fish (see Figure 1, 



