298 Salmonidz 
July, just before the running season, therefore coming in from 
the open sea. The great majority of the quinnat salmon, and 
probaby all the blue-back salmon, enter the rivers in the spring. 
The run of the quinnat begins generally at the last of March; 
it lasts, with various modifications and interruptions, until 
the actual spawning season in November, the greatest run being 
in early June in Alaska, in July in the Columbia, The run 
begins earliest in the northernmost rivers, and in the longest 
streams, the time of running and the proportionate amount 
in each of the subordinate runs varying with each different 
river. In general the runs are slack in the summer and increase 
with the first high water of autumn. By the last of August 
only straggling blue-backs can be found in the lower course of 
any stream; but both in the Columbia and in the Sacramento 
the quinnat runs in considerable numbers at least till October. 
In the Sacramento the run is greatest in the fall, and more run 
in the summer than in spring. In the Sacramento and the 
smaller rivers southward there is a winter run, beginning in 
December. The spring quinnat salmon ascends only those 
rivers which are fed by the melting snows from the mountains 
and which have sufficient volume to send their waters well out 
to sea. Those salmon which run in the spring are chiefly adults 
(supposed to be at least three years old). Their milt and spawn 
are no more developed than at the same time in others of 
the same species which have not yet entered the rivers. It 
would appear that the contact with cold fresh water, when 
in the ocean, in some way causes them to run towards it, and 
to run before there is any special influence to that end exerted 
by the development of the organs of generation. High water 
on any of these rivers in the spring is always followed by an 
increased run of salmon. The salmon-canners think—and this 
is probably true—that salmon which would not have run till 
later are brought up by the contact with the cold water. The 
cause of this effect of cold fresh water is not understood. We 
may call it an instinct of the salmon, which is another way of 
expressing our ignorance. In general it seems to be true that 
in those rivers and during those years when the spring run is 
greatest the fall run is least to be depended on. 
The blue-back salmon runs chiefly in July and early August, 
