144 THE LIFE OF THE SALMON 



seas in the winter months, but by the month of 

 April have risen in temperature so that the readings 

 in fresh water and the sea become equalised. Sub- 

 sequently, through summer, our rivers attain a 

 temperature considerably above that of the sea, but 

 by the month of September their temperature has 

 again fallen so that the conditions of sea and river 

 again equalise although now at a higher tempera- 

 ture than in .April. From September onwards the 

 winter conditions again become slowly established. 



During the warm conditions of summer, fish 

 ascending from the sea run up much more rapidly 

 than when the river temperature is low. Even in 

 May, fish are not infrequently taken well up our 

 rivers, i.e., thirty to even forty miles up, and still 

 bearing sea lice upon them, and with other unmis- 

 takable signs of having only very recently left the 

 sea. By this time the spring fish are making their 

 way to the head waters, where, as the season ad- 

 vances and their reproductive organs develop, they 

 become distributed in the manner so valuable for 

 the river's future stock. The summer fish having 

 rapidly moved up from the lower waters, the late 

 running fish, which enter from the sea with their 

 genitalia already well advanced the male fish being 

 at the end of the season not infrequently highly 

 coloured, as they come from the sea have, as it 

 were, those lower reaches left to them. In this way, 

 therefore, the waters of a well-stocked pure river are 

 fully taken advantage of for spawning, and are able 

 to return their best percentage of fry from all classes 

 of fish. 



