CHINOOK SALMON MARKING, COLUMBIA RIVER 267 



The chief purpose of this experiment was to furnish further information regard- 

 ing the conditions that determine whether a given chinook will return at maturity 

 as a part of the so-called spring or fall runs. Several experiments with the progeny 

 of the spring run have shown that a change in the early environment does not alter 

 the time of year at which the mature fish will start their spawning migration. This 

 experiment furnishes similar evidence regarding chinooks of the fall run. In this 

 case eggs from a run that enters the Columbia River during August and September 

 and spawns at a distance of approximately 150 miles from the ocean were trans- 

 ferred to a station at approximately five times that distance from the ocean, where 

 only a spring run of chinooks naturally spawns. 



If these fish were to become adapted to the conditions under which they spent 

 their early life, they would be expected to return to spawn in the headwaters where 

 they were liberated. They would be expected to store in their bodies a quantity of 

 fat sufficient to furnish energy for the long migration in fresh water. They would 

 also be expected to leave the ocean early enough to allow time for the long migration 

 before spawning time. None of these conditions seems to have prevailed. The 

 time at which they passed through the lower Columbia on their spawning migration 

 was no earlier than that of the Little Wliite Salmon River chinooks that remained 

 under natural conditions. As in the case of the latter, they appeared in the com- 

 mercial catches of the lower Columbia during the last two-thirds of August. None 

 of these fish returned to the Lemhi River, where they were liberated, nor did any 

 enter the Little White Salmon River, where the eggs were taken. In fact, none were 

 recovered as spawners. If any of them succeeded in passing the commercial-fishing 

 district, we have no knowledge of where they went or whether they succeeded in 

 reacliing suitable spawning grounds. Records of the quantity of fat stored in the 

 body of the fish were obtained for only four individuals. Although these records 

 were merely approximations based upon the appearance of the flesh, they indicate 

 that the quantity of fat was about average for fish of the fall run, which is much 

 less than that of chinooks of the spring run. 



The nuclei of the scales of the fish that were recovered in this experiment show 

 very httle variation. All have a central area of 12 to 19 rings (anterior radius 



r^ to rKr. millimeters) of stream growth, which in most cases is surrounded by a 



band of from 5 to 10 rings of intermediates. (See Table 33.) The stream growth 

 is broken by an incidental check, which incloses from 4 to 9 rings. A typical 

 nucleus is shown in Figure 85. Scales from fish recovered during th(>ir third and 

 fourth years are shown in Figures 83 and 84. 



CONCLUSIONS 



PERCENTAGE OF RETURN 



The reported returns from these experiments range from 1 out of 50,000 liberated 

 to 1 out of each 300 liberated. These figures have very little significance, however, 

 because they represent not the total returns but an unknown and varying proportion 

 of the total. As has been pointed out in the introduction, the authors and other 

 emploj-^ees of the Bureau of Fisheries who have assisted them with the collection of 

 data have been unable to observe personally more than n small fractio7i of the fish 



