118 THE LIFE OF THE SALMON 
the contrast between spring fish and autumn fish is 
also well marked. 
Tn 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. Noél 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 length gives the ultimate 
results :—~ 
Estuary. | Upper Water | Difference. 
grms grms. grms. 
May and June. . 6326 5839 487 
July and August . ‘ 6901 5887 1014 
Oct. and Nov. e : 6055 4116 1939 
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 0°75 per cent. in March to 17 per cent. in 
November. The average weight of ovaries per fish 
of standard length is given by Noél Paton and 
Dunlop in this form :— 
