METHODS OF INVESTIGATION. 



15 



in fresh water, and mainly from spawned fish, or those about to spawn. I 

 then studied the appearance of the scales, and particularly as to the extent 

 to which they were affected by the sojourn in the river and the act of 

 spawning. 



The edges of every scale taken from a clean well-fed fish caught in the 

 sea, or just after entering the river, resembles the one shown in Fig. 9 

 (Plate II.). Such scales I have classified as " unworn." Those which on 

 examination showed that they were affected by sojourn in fresh water have 

 been divided into four classes, viz., " slightly," " moderately," " much," and 

 ' excessively worn." These various stages are illustrated in Figs. 14, 15, 

 16 and 17 (Plates V. and VI.). The following table gives the results of 

 these investigations : 



An examination of this table reveals the following facts : 

 In the fish examined in the summer prior to the spawning season (see 

 the examples from Skoganvarre) the scales are found to be more and more 

 "worn" as the autumn approaches, On the other hand, of the fish 

 examined during the spawning season (the examples were taken from parent 

 fish used for artificial hatching) not one single individual has scales which 

 are unaffected. The extent to which the scales are worn is considerably 

 larger with the male fish than with females, and it is also more noticeable 

 during the later months of the year. It is probable, therefore, that the 

 wearing of the scales would be even more advanced by the time the spent 

 fish left the river as kelts and again returned to salt water and regained 



