FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 255 



measure, for the minor fluctuations in the time of appearance of the runs from year 

 to year and may be the cause of bimodality in the runs. Regardless of the primary 

 cause of this phenomenon, it would seem that there are two self-perpetuating com- 

 ponents of the red-salmon population in the watershed, and that each should be given 

 adequate protection. 



During the 16 years under consideration the spring runs have ranged from 303,000 

 fish in 1922 to 1,715,000 fish in 1926, the average being 817,000 fish. The fall runs 

 have ranged from 652,000 fish in 1929 to 3,205,000 fish in 1926, the average being 

 1,211,000 fish. The total run has ranged from 1,058,000 fish in 1922 to 4,920,000 

 fish in 1926, the average being 2,028,000 fish. Thus, there has been a rather wide 

 range in the number of fish in the runs from year to year, and the average run has been 

 far below that of the early days of the fishery when for a period of 7 years the catch 

 alone exceeded the run (catch plus escapement) during this period by more than 

 1,000,000 fish per year. 



RETURNS FROM KNOWN SPAWNING POPULATIONS 



In order to maintain the salmon runs at a high level, an adequate escapement 

 must be obtained for each and every suitable spawning area. The question at once 

 arises as to what constitutes an adequate escapement. This question has confronted 

 the salmon conservationist since the first attempt was made to regulate a fishery, and 

 it is a question that still needs considerable study. Each small section of a spawning 

 area must have its proper escapement, and in the final analysis, it is necessary to 

 determine, for each small area, the size of an adequate spawning population. The 

 problem is further complicated because an adequate spawning population for a given 

 spawning area is not necessarily constant. Variations in meteorological conditions 

 result in changes in environmental conditions on the spawning grounds during the 

 spawning and incubation periods from year to year, consequently, a spawning escape- 

 ment which may be adequate in one year may be inadequate, or may be more than 

 adequate, in some other year. As there is no means of predicting what meteorological 

 conditions will prevail during the spawning season and the subsequent incubation 

 period, we can at best determine an average figure for the optimum size of the spawning 

 population for each spawning area. 



Most of the progeny from a year's spawning population of Karluk red salmon 

 return as adults in their fourth to seventh year. 6 In order to determine the return 

 from the spawning of 1930, for example, it is necessary to determine the number of 

 4-year fish in the run of 1934, the number of 5-year fish in the run of 1935, the number 

 of 6-year fish in the run of 1936, and the number of 7-year fish in the run of 1937. 

 The numbers of these several groups are then added together to determine the total 

 return from the spawning of 1930. The returns from the escapements of the spring 

 run, from the fall run, and from the total run of each year are given in table 20. 



The escapement of 1921 (1,500,000 fish) produced a very good return both in the 

 ratio of return to escapement and also in the total number of fish produced. While the 

 return from the spring escapement was good, the return from the fall escapement was 

 much better and was largely responsible for the exceptionally good total return. 



• There are a few 3-year and 8-year fish in the Karluk runs which are included in the tabulations, but their presence is quite 

 unimportant. 



