MIGRATION OF SALMON IN COLUMBIA RIVER. 133 
River.® The question can be better understood when analyzed into the following points 
or questions: 
x. How long do salmon remain in brackish water? Or, stated more fully, how 
rapidly do salmon pass from salt water through the various degrees of brackish water at 
the mouths of the rivers? 
2. What evidence is there that salmon swim back and forth with the ebb and flood 
of the tide during the migration through brackish water? 
3. When once quite within the fresh water of the rivers, how rapidly and how 
continuously do salmon travel on their course up the rivers to the spawning grounds? 
4. What evidences do salmon give of special responses to unusual conditions, such 
as obstruction to their course, individual injury, etc. ? 
PRINCIPLE AND METHOD OF EXPERIMENT. 
This experiment is based on the principle that an understanding of the details of 
the migration phenomena can only be had by a study of the movements of individual 
fishes. The information derived from the movements of large schools of fishes, while 
often of extreme value as corroborative evidence, can never be taken as conclusive 
evidence of the movements of individuals. Even if it were safe to assume that the 
movements of a given school of salmon represent the average of the movements of the 
component individuals, yet it is quite impossible to identify certainly any given school 
at different points along the river. 
In order to subject the above questions to a preliminary test, I arranged a salmon 
marking experiment on the lower Columbia River. The experiment was accessory to a 
physiological investigation under my immediate direction during the summer of 1908. 
Fifty-nine fish were marked with individual tags and liberated in the Columbia River 
at the head of Sand Island, which is just within the mouth of the Columbia. The point 
at which the fish were liberated was about eight miles up the river above the Canby 
light-house on Cape Disappointment. This experiment was launched on August 14, 1908. 
Superintendent Nicholay Hansen, of the Chinook (Wash.) fish hatching station, 
contributed the catch of the Washington state fish trap. He also generously furnished 
transportation to the trap and granted me the assistance of the hatchery foreman and 
crew. I was assisted also by one of the staff of the United States Bureau of Fisheries. 
On the above date the trap contained a two-days catch. We reached the trap at 
about 9 o’clock in the morning, just before extreme low tide, and the net was lifted 
soon afterwards. The fish were run from the net into a special live car used by the 
Chinook hatchery crew to transport fish from the trap to the retaining grounds. 
The fish were later dipped from the car with a large dip net, lifted out of the net 
by hand, and quickly measured for total length. The marking tag was next inserted 
and the fish turned loose into the current. It goes without saying that the utmost 
a A briefer paper based on this experiment is published under the title, “An experimental determination of the speed of 
migration of salmon in the Columbia River,’’ in the Brooks Memorial Volume of the Journal of Experimental Zoology, vol. 9, 
1910. 
