232 BULLETIN OF THE BUREAU OF FISHERIES 



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This experiment adds more conclusive evidence to that given by experiment 

 No 5 regarding the influence of heredity on the time when the adult salmon return to 

 fresh water. In this experiment, as in experiment No. 5, the progeny of salmon that 

 enter the river in the spring were liberated in a tributary normally inhabited by fall- 

 running chinooks. Of the 47 recaptures reported from the commercial fishery, 40 

 were taken during May, and two-thirds of these were taken during the first 10 days 

 of the month. In other words, the run seems to have been well under way when the 

 season opened on May 1. With the exception of the one fish taken on July 15, 1924, 

 even those caught during June and July probably entered the river during May, as 

 their scales were greatly absorbed and the fish themselves were reported to be dull, 

 soft, and thin rather than plump and bright, as are fish that have recently left the 

 ocean. The condition of the fish taken on July 15 was not reported, but judging 

 from its scales, which were less absorbed than those of many of the fish taken during 

 May, there is no reason to believe that it had been in the river for any length of time. 

 The scales of the fish taken during September, 1922, were absorbed to an extent 

 indicatmg that the fish had entered the river some time before being caught; but 

 this alone is not sufiicient evidence to justify the conclusion that it left the ocean as 

 early as the majority of the fish returning from this marking. In view of the fact that 

 such a large proportion of the fish are known to have entered the river durmg a very 

 short period in the spring, the two possible exceptions need not affect the general 

 conclusion that the factors determining the time of entering fresh water are hereditary 

 and are not altered by conditions of early environment. Additional data regardmg 

 this important question are furnished by later experiments. 



The fact that salmon return to spawn in the river system from which they 

 migrated as fry or fingerlings, even though the eggs from which they developed may 

 have been taken from another river, has been demonstrated in many instances. 

 Gilbert (1919) has shown that sockeye salmon, of the Frazer River at least, return 

 to the particular spawning district in which they spent their early life. The authors 

 have numerous unpublished data that indicate that the same is true in general of 

 the chinook salmon of the Columbia. This series of experiments offers an unusual 

 opportunity to observe this tendency, both as regards natural and transplanted 

 runs. In this particular experiment fish were transplanted from one tributary to 

 another of the same system. The absence of heredity as a factor in determining 

 which tributary the resulting adult fish chose to enter is shown by the fact that a 

 constant search at the Willamette and McKenzie egg-taking stations (where the 

 eggs from which these fish developed were taken) revealed no marked fish. Their 

 failure to enter the WiUamette is shown further by the fact that the majority of 

 those recaptured were taken in the main Columbia River above the mouth of the 

 Willamette. Not only did they fail to return to the tributary in which they origmated, 

 but the majority also failed to return to the tributary in which they were reared 

 and liberated. Only one entered Herman Creek. This one, a female, was found 

 about 1 mile above the mouth of the creek on October 1, 1923. 



Herman Creek was observed on several occasions during the season of 1923, but 

 prior to the visit of October 1 it had not seemed necessary to look for fish above 

 the hatchery station, because a small dam used to divert water into the rearing 

 ponds had b^en impassable since late in May. The appearance of at least a dozen 



