54 



Appendices $fi Twenty-fifth Annual Report 



APPENDIX II. 



THE SCALES OF SALMON. 



By H. W. JOHNSTON. 



In the Twenty-third Annual Report (Part II., Appendix II.) I gave 

 an account of an examination of the scales of Tay grilse and salmon, and 

 oho wed that much useful information might be gathered from them as 

 to the life-history of the fish. Further investigation and recaptures of 

 •'marked" smolts, grilse, and salmon, have confirmed my deductions 

 and suggested some new points, which I now propose to refer to, 



When writing previously I divided my subject into three parts, 

 treating of 



I. Parr and smolts. 



II. Maiden grilse and salmon up to the time of their first return 

 to the river. 



III. Salmon that had previously returned to fresh water and 

 spawned. . 



It would occupy too much time and space to recapitulate the contents 

 of my first paper, and this must be read in connection with it. 



I. Parr and Smolts. (Plate I.) 



The difficulty of securing specimens of river parr of known ages 

 obliged me, in the Twenty-third Report, to limit my references to those 

 that had been artificially reared at Tugnet. The good and regular 

 feeding in confinement had caused these young fish to develope a larger 

 size and more scale ridges than we were likely to find in parr that had 

 to seek their food under natural conditions, and consequently the 

 indications afforded were in some ways misleading. 



During the last three years, however, some experimental work has 

 been done on the Tay with a small-mesh net, the results of which have 

 been recorded by Mr. Calderwood,* and this has given me the oppor- 

 tunity of examining natural parr and smolts taken during different 

 months. By comparing and classifying their scales one is able to 

 arrive at a fairly regular sequence in the number and arrangement of 

 lines put on while feeding in fresh or brackish water, and an 

 approximate estimate of age can in some cases be obtained. For this 

 purpose size and weight cannot be much relied on, as these are so largely 

 dependent on feeding. The number of ridges on the scale is also affected 

 by the same cause, and we cannot expect that a parr reared in the 

 cold and rocky waters of the Garry or Tilt will have the same chance 

 of obtaining food all the year round as one whose infancy has been 

 passed in the upper stretches of the Tay, where the water, regulated by 

 the loch, maintains a comparatively warm temperature in the winter 

 months. In fact, as I previously have stated, statistics based on the 

 number of ridges on the scale are not satisfactory, but, so far, I have been 

 unable to find any better method of comparison. The disadvantages are 

 perhaps more apparent when dealing with fish in their younger stages, 



* Twenty-third Annual Report (Part II., App. III.). Twenty -fourth Annual Report 

 (Fart II., App. TIT.). 



