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, 7.é., 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. 
