THE LOCH PROBLEM 191 
there is no apparent difference between the so- 
called Loch Leven trout which were put into 
the loch from the hatcheries and the little trout 
from my own burns. Numbers of these splendid 
trout running up to 5, 6, and 7 lb. must be the 
brothers and sisters of the little fingerlings of the 
same age in the burns. The best authorities are 
apparently agreed ^ that the average life of trout 
is about ten years (although there are authenticated 
instances in which they have lived for a much 
longer period), that they reach their prime in six 
or seven years, that they remain in their prime 
for a few years longer, and then begin to lose 
condition and weight as old age creeps on. Those 
of the trout put into the loch in 1910 and 1911 
which I have described as of fair size were about 
three to the lb., some rather larger and could not 
then have had many years to live. Those from 
the burns were probably of different ages, but 
it is highly likely that in 1913 and 1914, when the 
yearlings from the hatcheries were put into the 
loch, there were very few of such other trout 
^ See, for instance, the opinions of Mr. F. M. Halford in The Dry- 
Fly Man's Handbook, p. 395 (George Routledge & Sons, Ltd., London) ; 
Mr. P. D. Malloch at p. 179 in the work previously cited; Mr. .J. J. 
Armistead in An Angler's Paradise, and how to obtain it; and Mr. Tom 
Speedy in The Natural History of Sport in Scotland with Rod and Gun 
(William Blackwood & Sons, Edinburgh and London, 1920). 
