SEAWARD MIGRATION OF CHINOOK SALMON. 5 



effective collecting was not begun until October. Collections were made chiefly on the 

 lower Columbia between the mouth of the Willamette River and the ocean during Octo- 

 ber, November, and December, 1915. Owing to the unusually severe winter of 1915-16 

 the river contained so much ice that further collecting had to be deferred until March, 

 1916. From March until September frequent samples were taken at various points. 

 These collections made in the Columbia River in 1914, 1915, and 1916, the collections 

 from the Sacramento River mentioned above, and certain collections from the smaller 

 coastal streams in California and Oregon contained in the Stanford University collec- 

 tion constitute the material on which this paper is based. 



Thanks are due especially to Dr. C. H. Gilbert for assistance and advice given freely 

 throughout the course of this investigation. The author is indebted also to Henry 

 O'Malley, in charge of operations on the Pacific coast, and to Supts. Dennis Winn and 

 Hugh C. Mitchell, of the U. S. Bureau of Fisheries, for advice and assistance in the collec- 

 tion of material. The friendly cooperation of the Oregon Fish and Game Commission, 

 through Supt. R. E. Clanton, has also been of great assistance. John Larson, of the 

 Oregon Fish and Game Commission, accompanied the writer on many of the collecting 

 trips during 1916 and proved an invaluable assistant. To N. B. Scofield, of the Cali- 

 fornia Fish and Game Commission, acknowledgment is due for permission to examine 

 young salmon collected by him from the Sacramento River. Mrs. W. H. Rich aided 

 in the preparation of scales for study and in the correction of manuscript. 



STATEMENT OF THE PROBLEMS. 



On beginning this work in June, 191 4, the following tentative list of the more im- 

 portant problems relating especially to the Columbia River fisheries was made as a 

 guide for determining the character of the future work : 



1 . What is the value of the hatchery work done on the river ? Do the chinook fry 

 planted from the hatcheries return as mature fish; and if so, when, and in what 

 proportions ? 



2. At what ages do the young migrate to the ocean? What proportions migrate 

 at the different ages, and what are the sizes of these migrants ? 



3. What age groups are represented in the different runs of the various species 

 (chinook especially), and what are their average sizes and weights? Do these sizes and 

 weights vary during the season ? 



4. What are the proportions in which these age groups are represented, and do the 

 proportions vary during the season ? 



5. What are the relative sizes and proportions of males and females? 



6. What results are being obtained from the marking experiments started in 191 1 

 on the Sacramento River ? 



In addition to the above problems it was very soon found that one of the most im- 

 portant practical problems on the Columbia River has to do with the difference between 

 the spring and the fall runs of chinook salmon. This has been kept in mind, therefore, 

 throughout the work. The spring fish are much more valuable than the fall fish, being 

 richer in oil and of better color, and the great desire of the commercial fisheries is to 

 increase the spring run. It is obvious that the only opportunity to influence the history 

 of the salmon is during the early life in fresh water before the young have migrated to 

 the ocean. To do this intelligently, an exact knowledge of the early history, previous 



