CONDITIONS OF A GOOD GRILSE YEAR. 99 



the sea in the winter and early spring months ; 

 yet for some unknown reason they never attempt 

 to make the journey to fresh water with the 

 adult fish at that time. It has been proved 

 beyond a doubt that the habits of salmon depend 

 chiefly upon the temperature of the water, and in 

 my opinion grilse do not begin to run until the 

 temperature of the fresh water is higher than in 

 winter. The sudden change from comparatively 

 warm salt water to cold fresh water in winter and 

 spring is injurious to them, as grilse are in the 

 immature stage, and therefore they remain in the 

 sea until their instinct leads them from it. They 

 seem to be aware when our rivers have reached 

 a certain height of temperature, and that is not 

 until April or May, or even the beginning of June. 

 It is true that salmon in the parr stage can live 

 and thrive in very cold water, but then they have 

 been born and bred in it, and therefore acclima- 

 tized to the cold ; but with all that, they do not 

 care to migrate to sea and be transferred to a 



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