258 BULLETIN OF THE BUREAU OF FISHERIES 



taken from the Columbia during the time when these experiments were in progress. 

 It has been necessary, therefore, to depend upon fishermen and cannery employees 

 for most of the records of returning marked fish. The number of persons who have 

 searched for marked fish and the conditions that affect the efficiency of their efforts 

 have varied so greatly as to make it impossible even to estimate with any degree of 

 accuracy what proportion of the total recaptures have been reported. The apparent 

 failure of some of the early experiments probably was due in part to the fact that no 

 inducement was offered to those finding marked salmon to report their captures. 

 The first real interest on the part of fishermen and cannery employees came in 1920 

 as a residt of the Oregon fish commission's offer of a reward of 50 cents for each record 

 of the capture of a marked fish. An increase in the reward to $1 in 1922 caused a 

 greater response from those connected with the industry, but even with this induce- 

 ment a great deal of encouragement and publicity was required to get people started 

 reporting their captures. The system of collecting data has been improved con- 

 stantly, until daring the last few years it is believed that most of the recoveries have 

 been reported. 



Another source of error is in connection with the escapement; that is, those 

 fish that succeeded in evading the commercial gear and continued on to the spawning 

 grounds. In the experiments involving fish from Little White Salmon River and 

 Big White Salmon River, nearly all of the escaped fish probably returned to their 

 parent tributary and were caught in the course of the egg-taking operations. This 

 is not true, however, of experiments involving chinooks of the spring run, the greater 

 part of which did not enter the tributary in which they were liberated but continued 

 on up the Columbia. No record is available of those that succeeded in passing the 

 upper limit of the commercial fishery. 



In view of the many sources of error it is useless to assign the experiments to 

 rank in the order of success; but so little is known of the residts of either natural or 

 artificial propagation that even an approximation of the general success of these 

 experiments will be of interest. Experiment No. 12 was the most successful, the 

 reported recoveries representing 0.45 per cent of the fingerliugs liberated. Experi- 

 ment No. 7, with the reported recoveries representing 0.39 per cent of the liberation, 

 stands second. The records of this experiment are not accurate, in that they do not 

 include the escapement, which continued on up the main Columbia beyond the 

 commercial-fishing district. Third in success is experiment No. 6, with 0.24 per cent 

 recovered. Here again the escapement is not represented. Experiment No. 8, 

 with 0.18 per cent recovered, is fourth. In these four experiments the records from 

 the commercial fishery are believed to represent the majority of the marked fish 

 that were caught. The returns that have not come to our attention certainly would 

 ndt add enough to make the totals more than 1 or 2 per cent of the liberation. 



SUCCESS OF LONG AND SHORT PERIODS OF REARING 



One of the most important problems confronting those interested in the artificial 

 propagation of salmon is the determination of the length of time the fingerlings should 

 be held at the hatchery in order to get the greatest return. Some hatchery men 

 prefer to liberate theu- fingerlings very soon after the yolk sack is absorbed, whereas 

 others are of the opinion that best results are obtained from much longer rearing. 



