580 
CHARLES WILSON GREENE 
The Pacific salmon is an unusually favorable fish upon which to 
determine the factors in migration. It has been known for a 
number of years that these fishes spawn in the cold waters of 
fresh water streams, usually in the mountains. The eggs are 
hatched and the young are developed to the fingerling stage and 
then migrate down the rivers to the sea. In the sea they feed 
a number of years until maturity. When maturity is reached they 
reenter the estuaries of the rivers, ascend the rivers to spawning 
grounds and deposit their eggs. In the case of all the species of 
the genus Oncorhynchus the fishes die after they once spawn. 
They do not again return to the salt waters of the ocean. 
When a salmon once enters the fresh water rivers, it, seemingly, 
makes a pretty direct run to the spawning grounds. This run 
often extends over several hundred miles and ma}'" consume as 
much as two or three months of time. When the fish enter the 
rivers they are in the very finest physical condition. Their 
muscles are developed apparently to the fullest extent and their 
tissues as a whole are loaded with nutritive material, i.e.y fat. 
This is the result of the long months of feeding during the life in 
the ocean. Apparentl}^ the ocean furnishes rich feeding grounds 
and is visited for the distinct purpose of supplying a more favor- 
able condition of nutrition. When the fish enter the fresh waters 
for their long journey they stop feeding absolutely, a fact that is 
well known for the Atlantic salmon from the work of Miescher 
and of Noel Paton. These facts in the case of the Pacific salmon 
have been determined by the observations of numerous investi- 
gators of the United States Bureau of Fisheries. Putter particu- 
larly has shown that the salmon not only does not eat but that 
the digestive tract diminishes sharply in size during this fasting 
period. I have confirmed Putter's work for both the Sacramento 
and the Columbia River regions. 
This migration of salmon in fresh water is a period of strong 
activity. The fishes make their way up the streams against strong 
rapids and sharp water falls. Before passing the latter obstruc- 
tions salmon will ofttimes leap the falls in many unsuccessful at- 
tempts, even jumping to the extent of six or seven feet in height 
"and against the known swiftness of the water under such condi- 
