THE LIFE OF THE SALMON 235 



acquire the average weight which grilse are supposed to have, 

 viz., from three to six pounds, but would be of considerably 

 smaller size. 



THE RETURN TO FRESH WATER 



There are varying periods in which the smolts of any 

 one year's descent may return to fresh water. 



The first of these to return are then known as grilse, 

 and they may appear at any time from June to December 

 in the year following their descent as smolts to salt water. 



The next to return are known as small spring fish (salmon). 

 These will appear in the spring following that in which the 

 grilse return, and these salmon will in their turn be followed 

 in the summer and autumn by the summer and autumn 

 salmon respectively. 



The dates of the return of the salmon for the first time 

 to their own river should not be considered as being due to 

 any other cause than that the opportunity and the desire 

 to run are co-incident. When circumstances are favour- 

 able and the fish are willing, then will they make their 

 up-stream run but when circumstances are not so favour- 

 able, or when they are not desirous, they will not do so. 



These varying times for the return of salmon to fresh 

 water have been alluded to by different writers as divided 

 immigration, and by some have been considered as denoting 

 different types of salmon. 



THE GRILSE OR SALMON 



Here again meteorological conditions affect his move- 

 ments, and when the condition of the water in the river up 

 which he has to ascend is favourable, his instinct again 

 sets him going. It is now that all the strength and stamina 

 won during his salt-water experience is required to carry 

 him safely through the perils and the difficulties of the 



