The Salmon 4I 



migration. I think it would be absurd to call the tish a belated grilse 

 we caught on 9 th August (Fig. 28), weighing 27 Ibs., on its first 

 return from the sea, or a 6o-lb. fish arriving from the sea for the first 

 time at the ripe age of seven years. 



The marking of the smolts and their recapture afterwards has 

 enabled us to know for certain whether the small spring fish will be 

 plentiful or scarce, and what the other runs that follow will be, long 



FIG. 37. Showing mark of first small Spring fish, 9^ Ibs., caught iSth February 1907. 



Marked as Smolt May 1905. 



before the fish enter the river, and it also enables us to tell whether 

 the fish will be large or small. 



I will now return to the grilse from 4 to 13 Ibs. that run from the 

 middle of May to the middle or end of December. These spawn the 

 same season as they come up and become kelts (Fig. 38). Many of 

 them, both male and female, die after spawning, the mortality amongst 

 males predominating. A few of those that return to the sea re-enter 

 the rivers as clean fish, after being three or four months in the sea. 

 On their return about June they are double the weight they were 

 when they went down, and as the season advances the number and 

 weight increase. We know this from marking the kelt grilse. 



Until a year ago we called all these fish that returned bull-trout, not 



6 



