118 THE LIFE OF THE SALMON 



the contrast between spring fish and autumn fish is 

 also well marked. 



In dealing with fish from different rivers, it was 

 necessary to calculate a standard fish length with 

 which to make comparisons. This having been 

 arrived at, not only weights of fish but weights of 

 muscle and genitalia could be dealt with on one 

 basis. In estimating the nutrition of fish in estu- 

 aries as compared with those from upper waters, 

 Drs. Noel Paton and Dunlop received material from 

 the Spey, the Helmsdale, and the Dee. The weight 

 of the muscle was worked out in every case, and the 

 following table showing the average weight of muscle 

 for fish of standard le'ngth gives the ultimate 

 results : — 



In the upper water fish a loss in weight of muscle 

 works out to nearly 28 per cent. 



In contrast to this, the increase in weight of the 

 ovaries of female fish is most marked. In the Tweed, 

 Grey and Tosh, treating this subject in percentages 

 to the weight of the fish, had already shown a change 

 from 075 per cent, in March to 17 per cent, in 

 November. Tlie average weight oj ovaries 'per fish 

 of standard length is given by Noel Paton and 

 Dunlop in this form : — 



