METHODS OF INVESTIGATION. 



9 



much later, the last winter-band i quite close to the edge of the scale. We 

 also find the same to be the case in the scales of the large fish (Fig. 12) 

 caught in the month of May. It is therefore evident that in Norway also 

 the ring formation at the edge of the scale corresponds to the period of the 

 year when the fish was caught. After examination and analysis of the 

 scales of several thousand salmon, I find that in the majority of the large 

 fish caught at the beginning of the season the last complete winter-band 

 lies close to the edge of the scale, whereas in small fish caught at a later 

 period the summer-zone outside the previous winter-band is always broader 

 and contains a greater number of rings. 



This fact is further illustrated by the following table, which contains an 

 analysis of the various positions of the last winter-band in relation to the 

 edge of the scale, and is based on the examination of 262 salmon caught 

 along the Mandal coast from May to July, 1909. This analysis is based on 

 an approximate estimate of the relative width of the summer-zone lying 

 between the last completed winter-band and the edge of the scale, and must 

 therefore not be taken as absolutely accurate. It clearly indicates, how- 

 ever, that the formation and growth of the summer-zone takes place during 

 the summer months, and that this zone increases in width as the season 

 advances. It also shows that in a number of fish caught in May, and even 

 in June, the winter-band lies close to or is actually on the outer edge of the 

 scales. 



ANALYSIS OF THE SCALES OF 262 SALMON FROM THE COAST NEAR MANDAL. 



It is most exceptional for any salmon to be caught in the sea in Norway 

 during the winter months, and it was therefore impossible to obtain material 

 in order to ascertain the appearance of the scales during the winter season. 

 I therefore requested Dr. Holt to send me from Dublin the scales of a 

 number of salmon caught in Ireland during the early spring and summer of 

 1909. This material has been examined and analysed as above in order to 

 ascertain the position of the last winter-band. The results are given in the 

 following table : 



