KARLTJK RIVER RED-SALMON INVESTIGATION 



9 



by three poor years — the good years are those ending in the figures 1, 2, 6, and 7, 

 and the poor years end in the figures 3, 4, 5, 8, 9, and 0. This is well shown by 

 the line of the mean, which is also shown on the graph. 



The last cycle, that involving the years 1921-1925, differs from the others in 

 that the second year is conspicuously the poorest one of the series. The other four 

 years of the cycle, however, do conform very well with the corresponding years of 

 the other recent cycles. Something obviously happened to reduce the yield of 

 1922 below that of the corresponding years of previous cycles. 



No one can examine such a series of data without being impressed by the con- 

 spicuous correlation between the size of the catch in the corresponding years of 

 the several cycles. There is a remarkably uniform tendency in each cycle, as shown 

 on the graph, for the catch of the second year to be smaller than that of the first, 

 for that of the third to be smaller than that of the second, for the catch of the fourth 

 year to be about the same as that of the third, and for that of the fifth year to be 

 greater than that of the fourth. If it can safely be assumed that spawning escape- 

 ments are in the main roughly proportional to the catch, it becomes apparent that 

 they are the predominating factor in determining the size of the runs. 



That other factors may intervene is shown by the sudden drop in the catch 

 from 1917 to 1922. The catch in 1917 was 2,324,492, while that in 1922 was only 

 658,159 — one of the poorest on record since the fishery became well established. 

 This is discussed in detail hereafter in the section entitled "Analyses of recent runs." 



OBSERVATIONS ON THE SPAWNING GROUNDS 



For its size, the Karluk River probably supports the most magnificent run of 

 red salmon of any known stream — at least, of any stream on the American side of 

 the north Pacific — and it has maintained this run in fair measure in spite of the 

 very intensive fishery which has been conducted at the mouth of the river for more 

 than 40 years. From time to time representatives of the Bureau of Fisheries have 

 visited the lake and recorded something of the conditions found there during the 

 spawning season. The earlier observations were only occasional and largely of the 

 nature of general surveys. Eight years ago, however, the senior author of this 

 paper undertook a more detailed and intensive study of the Karluk red salmon, and, 

 as a part of this, regular yearly surveys of the spawning grounds have been made. 

 At first these were intended to supply some measure of the extent of the spawning 

 escapement, but a much more accurate measure of the escapement (by means of 

 weirs, through which the fish are counted) was later adopted and has been in use 

 since 1921. The observations on the spawning grounds are of great value, how- 

 ever, in showing the conditions under which the spawning takes place, and will help 

 materially to determine the relative success that may be anticipated from the suc- 

 cessive spawnings. 



There are only two published accounts of observations of the spawning in 

 Karluk Lake — those of Bean 3 and Chamberlain. 4 



! Report on the salmon and salmon rivers of Alaska, with notes on the conditions, methods, and needs of the salmon fish- 

 eries. By Tarleton H. Bean. Bulletin, United States Fish Commission, Vol. IX fj 1889. (1891), pp. 165-208, Pis. XLV-LII. 

 Washington. 



* Some observations on salmon and trout in Alaska. By F. M. Chamberlain. Report, United States Commissioner of 

 Fisheries for 1908 (1908). Bureau of Fisheries Document No. 627, 112 pp., illus. Washington. 



