THE SPAWNING PERIOD 



171 



consecutive years, the first fish, being recaptured in the Clyde estuary, 

 might quite conceivably not have ascended the Leven to the loch. 



Of 24 fish marked in the Altnagairoch Burn, a small tributary of 

 Luss Water, in 1913, two were recaptured: — 



8331 B. Marked, Altnagairoch Burn 

 Recap., Altnagairoch Burn 



8328 B. Marked, Altnagairoch Burn 

 Recap., Altnagairoch Burn 



while, again, of 16 fish marked in the Smiddy Burn^ in 19 13, two were 

 recaptured also in 1914: — 



8346 B. Marked, Smiddy Burn ( ?)i 



Recap., Al'gairoch Burn(?) 



8347 B. Marked, Smiddy Burn ... 



Recapt'd, Smiddy Burn ... 



all four of which prove returns in two consecutive years. 



It is fair comment, I think, that if fish of varying weights are each 

 found spawning in two consecutive years, there is at least a presump- 

 tion that all may really spawn over more than two consecutive years. 



But what ought perhaps properly to be called secondary proof is 

 furnished by the scales of some of the recovered marked fish and of 

 others unmarked. I shall examine first such scales as I have of marked 

 fish — accepting as correct, as I confidently do, the readings agreed upon 

 between Mr. Hutton and myself — as in their case the evidence obtained 

 from marking is so far placed beyond question. 



I. In Fig. 55, I reproduce the scale of the sea-trout, a male fish, 

 which is referred to above as having been marked with label No. 

 8331 B in the Altnagairoch Burn, Luss, in November 1913, and 

 recovered in the same burn when spawning again in November 19 14. 

 The photograph shows how greatly the scales of male fish become 



1. See note in text, p. 126. 



