52 THE AGE AND GROWTH OF SALMON AND TROUT. 



in quite different years, and originate from a series of different spawnings 

 the effects of which have been spread over six or seven successive years. 



There has been a very widely-spread belief that the results of a successful 

 smolt year or spawning year after the lapse of a definite interval of time 

 as to the length of which there were many different theories would again 

 show themselves in the form of a year of plentiful salmon or large catches. 

 As can now be seen, the results of any one spawning good or bad are 

 spread over the catches of six or seven years, and in such a manner that it 

 seems improbable that we shall be able by means of statistics to show any 

 remarkable difference in the effects of the different spawnings. In any case, 

 in attempts to solve this problem we should have to reckon with so many 

 doubtful points that the results would be most untrustworthy. A closer 

 examination of the table shows this most clearly. Amongst other things it 

 is at once evident that similar conditions do not prevail in the south and in 

 the north, owing to the fact that in various years different year-classes con- 

 stitute the bulk of the catch in different localities. 



What, however, must at once strike one, is the remarkable manner in 

 which this distribution of the product of each year's spawning must operate 

 for the preservation of the species. When the results of any one spawning 

 are spread over the catches of so many years, and when they are scattered 

 so heterogeneously during different years throughout the various districts, it 

 must in the highest degree tend to work as a sort of insurance for the species, 

 and as a division of the risk attached to each individual fish. 



