18 THE LIFE OF THE SALMON 
fish would be allowed to remain in better proportion, 
and the spawning season would in time harmonise 
with the normal. A long belt of netting in a 
river renders the weekly close time inoperative : 
all early fish are captured, and only late-running 
fish remain to keep up the stock. The statement 
is by no means speculative. As will be shown at 
greater length in a subsequent chapter, physio- 
logical investigations of the most exhaustive kind 
have shown that in widely different rivers geogra- 
phically the ovaries of the salmon reach maturity 
with remarkable seasonal uniformity. 
Reference has been made to the great variation 
in the rate of growth of artificially reared smolts. 
This does not seem to exist in the natural state. In 
a series of smolt-netting experiments recently 
made in the waters of the Tay below Perth it has 
been found that, while various sizes of parr are 
present, the silvery or migratory smolt is wonder- 
fully uniform in dimensions. Great numbers of 
smolts were passed under observation, and batches 
were measured at intervals. They were found 
to be from 5 to 6 inches in length (measuring to 
the centre of the forked tail), and to weigh from 
1 to 2 ounces. The netting and marking of Tay 
smolts was commenced in the spring of 1903.* The 
part of the tidal water where the fish weré found 
in greatest numbers was about four miles below 
Perth. The river above this point is affected by 
the tide for several miles, but the fresh water is 
* Twenty-third Report, Fishery Board for Scotland, Part II. 
Appendix ITT. 
