214 U. S. BUEEAU OF FISHERIES 



PACIFIC COAST AND ALASKA INVESTIGATIONS 

 ALASKA SALMON 



One of the greatest responsibilities resting upon the bureau is 

 that of advising the Secretary of Commerce in the administration, 

 under the White Act of 1924, of the fisheries of Alaska. If these 

 fisheries fail, the bureau is responsible in large degree ; if they pros- 

 per, the credit must be given to the wisdom and knowledge employed 

 in drafting the fishery code and to the courage and faithfulness Math 

 which the regulations are being enforced. The bureau has made great 

 strides during the last decade in acquiring that exact and intimate 

 knowledge of the biology of the salmon necessary for the wise 

 husbanding of the supply. 



Although many workers were engaged in the early investigations, 

 undoubtedly the greatest contribution was made by the late Dr. C. H. 

 Gilbert through his studies on the biology of the various species of 

 salmon; and although the investigations in recent years have devel- 

 oped along more practical lines than formerly, each year's work has 

 been a continuation of that for which comprehensive plans were 

 made several years ago, and each year finishes one more chapter in a 

 continued story. The aim of the investigation up to the present 

 time is concisely given in Doctor Gilbert's own words, as follows : 



The principal aim of this work is to ascertain what relation exists between 

 spawning colonies of varying size and the number of progeny that they furnish. 

 For this crucial experiment we have chosen, as most favorable, the Karluk 

 and Chignik Rivers and the streams entering Olga Bay. The annual weir 

 counts give us the size of the spawning colonies, and the weir counts plus the 

 commercial catches give us the total returns to these streams. But as the 

 progeny of any year mature at various ages, it becomes necp^sary, in order 

 to ascertain the returns from any single spawning, to analyzf the runs to the 

 experimental streams and to determine in what proportions fish of different ages 

 appear in these runs. To do this, it is necessary to examine extensive samples 

 taken at frequent intervals during the runs, making age detenninations through 

 the miscroscopic structure of the scales, and by the results thus obtained to 

 compute how many 3, 4, 5, 6, and 7 year fish comprise the run of each year. 

 When that is carried out over a term of years, it becomes possible to sum the 

 total progeny of any spawning, which have appeared as fish of different ages 

 in a series of successive runs. 



From time to time it is possible to sum: the results and draw conclusions 

 that are believed to have both scientiflp and practical value. Such an attempt 

 was made last year by Doctor Rich and me for the investigations made to date 

 in the Karluk watershed. (See Doc. No. 1021.) We announced in this paper, 

 tentatively, a rate of increase from spawning parents to progeny of approxi- 

 mately three to one and on this basis ventured a prophecy that the total run 

 of red salmon to the Karluk River in 1927 should not exceed 1,500,000 fish. 

 The run that actually occurred, including weir count plus commercial catch, was 

 approximately 1,641,000. (The run of 1926 had exceeded 4,600,000.) We do not 

 beiieve it possible to predict as closely as this the runs of successive yeai'S, but 

 we do believe that by this method a more reliable basis for prediction may be 

 ascertained than has been available in the past. 



The work done annually in connection with these experiments is of a highly 

 routine nature — the examination of many thousands of salmon scales, the tabu- 

 Jation of the results, and the attempt to draw from these such generalizations 

 ■of value as seem warranted by the facts. In addition to the above, we are 

 attempting to ascertain, for all the principal red-salmon streams in Alaska 

 and especially for those in Bristol Bay, the prevailing age cycle of each, so as to 

 vdetermine what were the brood years for each successive run. 



Tagging experiments. — Additional tagging experiments in the 

 channels of southeastern Alaska were conducted during 1927 under 



