CHINOOK SALMON MARKING, COLUMBIA RIVER 219 



scales, and the locations of the fins are indicated clearly by an abrupt change in the 

 contour of the body at that point and by a slight growth of scar tissue. Fish lacking 

 the ventral fins and appearing as those described by Marsh and Cobb have been 

 observed by the present authors, but invariablj' these fish have had all other fins 

 present and normal, indicating that they were not marked fish of this series. Further- 

 more, the pelvic bones invariably were absent, which would indicate further that 

 the scars were not the result of amputation but probably were caused by abnormal 

 development. During the marking of many hundreds of thousands of young salmon 

 we have observed fish occasionally with one or both ventral fins missing. Possibly 

 one fish in ten thousand will show this abnormality. It has been noted also that the 

 adipose fin is missing in about the same number of fish, but we have never observed 

 a case in which both the adipose and the ventrals were affected. The theoretical 

 probability of finding such a case in nature wou'd be about one in one hundred million, 

 a contingency so remote as to be of no practical importance whatsoever. 



During the years that the Columbia River marking experiments have been in prog- 

 ress. Dr. J. O. Snyder, of Stanford University, has conducted a similar but less extensive 

 series of experiments in California.'' His method of marking and other details of his 

 experiments have been nearly identical with ours, and his results also have been 

 approximately the same. The outstanding features of his results are as follows: 

 Salmon marked on the Ivlamath River were found in the ocean as far south as Mon- 

 terey Bay; those marked on the Sacramento River were found in the ocean both north 

 and south of the mouth of that river. Notwithstanding this extensive migration, all 

 returned at maturity to the river system in which they were liberated. The pro- 

 portion of marked fish recovered was approximately the same as in the Columbia 

 River experiments. The scales of the adult fish have been found to be a correct and 

 reliable record of the age and life history of the fish. 



Snyder recently conducted an experiment designated to determine the more 

 minute details of the homing instinct of salmon. Satisfactory returns were obtained 

 from this experiment during the seasons of 1926 and 1927, but the results have not 

 been published. 



The collection of data from returning adults has proved difficult. One of the 

 authors or some other representative of the Bureau of Fisheries has spent the greater 

 part of each season in the commercial fishing district searching for marked salmon; 

 however, the one or two persons could observe only a small proportion of the salmon 

 taken from the river, as the fish are divided between about 20 canneries distributed 

 along 200 miles of the river. It has been necessary, therefore, to depend largely 

 upon assistance from fishermen, cannery employees, and hatchery men. Theodore 

 F. Rich and W. H. Spaulding aided materially in this work during the seasons of 1919 

 and 1920. The greatest assistance was rendered by the Oregon Fish Commission, 

 which since 1920 has paid i-ewards for records of the recovery of marked fish. During 

 1920 and 1921 a reward of 50 cents for each record was offered. From that time until 

 about the middle of the season of 1926 the reward was $1, but because of the many 

 records of marked sockeye salmon recovered during 1926 it became necessary to 

 reduce the rewards to 50 cents during the latter half of the season. A reward of 50 



< See Snyder, 1921, 1022, 1923, and 1924. 



