66 Appendices to Twenty-fifth Annual Report 



DESCRIPTION OF PLATES. 

 PLATE I. 



Scales of Parr and Smolts. Magnification x 22. 



1 



Fig. 



Age 

 about 



Size. 

 Cm. 



Captured. 



Remarks. 





— Years. 







1 Parr. 



r 





6-8 



May 1905, tidal 

 water. 



Growth larger on posterior 

 area. 



2 Smolt. 



2 



o 



13 8 



May 1904, tidal 



Lines of third summer 







M 





water. 



forming. 



3 Parr. 







11-6 



July 1905, Upper 





V 





Tay. 



j> Probably hatched early. 



4 Smolt. 



2 





16-3 



April 1906, tidal 

 water. 



5 Parr. 







9-4 



Mar. 1907 ) Stor- 



>montfield 



Parr and scale compara- 

 tively large. 



6 Smolt. 



\ 



o 



< 



161 



,, 1906 J ponds. 



Wide lines of second sum- 











mer distinct. 



PLATE II. 



Scales of " wired " grilse which had been marked when migrating as smolts in 1905 

 and were recaptured in the summer of 1908. 



Fig. 1. Scale of a 2^-lb. grilse caught 1st June 1906, showing feeding in the sea during 



a summer, winter, and early part of a second summer. 

 Fig. 2. Scale of a 9-lb. grilse caught 17th August 1906. This grilse had remained longer 



in the sea, and the additional growth is represented by the increase in the 



number of lines exterior to the annual ring, all of which were formed in its 



second summer. 



PLATE III. 



Fig. 1. Scale of a 9^-lb. small spring salmon which had been marked when migrating as 

 a smolt in 1905, and was recaptured on 18th February 1907 when perhaps six 

 months older than the August grilse of nearly the same weight (Plate II., 

 fig. 2). The second annual ring is seen on the margin of the scale, where it 

 surrounds the wider ridges of the second summer. These ridges are numerous 

 but rather irregular in formation, and suggest that there is some difference in 

 the feeding habits of small spring fish and grilse. 



PLATE TV. 



Scales of marked fish (No. 9194 Tay) subsequently recaptured. 



Fig. 1. Scale of 5|-lb. grilse kelt taken on 11th April 1906, showing one annual ring 

 followed by the lines of the second summer. 



Fig. 2. Scale of the same fish when recaptured as an llj-lb. clean salmon on 9th August 

 1906. The new growth put on in the sea after the kelt stage completely sur- 

 rounds the older material, and the junction is denoted by an irregular fissure 

 (spawning mark). 



In comparing scales taken at different times from the same fish it must be remem- 

 bered that it is almost impossible to get two that are exactly identical in formation, and 

 there may be some slight differences in minor details. 



PLATE V. 



Scales of marked fish (No. 1180, Helmsdale) subsequently recaptured. 

 Fig. 1. Scale of 5-lb. kelt taken on 12th December 1904. Two annual rings are followed 

 by a few lines of a third summer which correspond in number to what we find 

 in fish entering the river in May or June, so that this kelt had probably been 

 in fresh water for perhaps six months before it was marked. 

 Fig. 2. Scale of the same fish when recaptured as a 14-lb. clean spring salmon on 30th 

 April 1906. The new growth is added round the circumference of the kelt 

 scale, and its ridges are at first widely apart as a result of summer feeding, 

 while the more exterior lines are contracted towards the margin of the scale 

 and form a winter ring. The spawning mark is apparent all round, but in a 

 thick scale photography does not bring it out so clearly as in a thinner one. 

 Note. — In Plates II., III., IV., V. the magnification is x 15. The vertical lines 

 opposite the figures indicate the extent of the growth of the anterior area of the scale. 

 The annual rings which occur towards the end of winter and approximately mark the 

 completion of a year in salt water, are indicated. There is no increase in the area of the 

 scale of the salmon while in the river, and therefore no annual ring is formed during a 

 winter when a fish is spawning, though there may be slight traces of it on the scales of 

 fish that have descended as very early kelts. 



