42 U. S. BUREAU OF FISHERIES 
1926. With the establishment of a counting weir in the river in 
1921, and the passing of the White Law in 1924 (48 Stat. 464), a 50 
percent escapement of fish to the river has been required. ‘This 
limited escapement has curtailed the commercial catch in the area, 
and since 1924 the total run of red salmon to Karluk has exceeded 
2,000,000 fish in only 8 years; in only 2 of these 8 years did the total 
run exceed 3. 000,000 fish. 
In view of the decline in the productivity of the Karluk River 
every effort is being made to determine its cause, with special 
emphasis on the factors responsible for the mortality of red salmon 
during their fresh-water and marine existence. Because of the greatly 
varying environmental conditions in the river system, it has been 
found that the number of mature salmon necessary to adequately 
seed the spawning grounds may fluctuate considerably from year to 
year. The mortality of the salmon duri ing their fresh-water exist- 
ence has been traced to the influence of environmental conditions on 
the spawning grounds and to seasonal fluctuations and_ periodic 
trends in the fertility of the lake, which are responsible for corre- 
sponding variations in the abundance of the food available to the 
young fish and the influence of fresh-water predators. 
An intensive study has been made of the mortality of the red 
salmon during their marine existence by means of consecutive yearly 
marking experiments from 1926 to 1936, inclusive. The results of 
this study indicate that there is a fairly constant mortality of the 
salmon in the ocean which averaged 79 percent during the 8-year 
period of study. 
A complete report of the activities and results of this investigation 
of the Karluk red salmon, from 1926 to 1936, has been prepared 
by J. T. Barnaby and submitted for publication. Mr. Barnaby con- 
ducted this investigation from 1929 to 1988 and then was transferred 
to the Bristol Bay ‘investigation. 
Migration studies —Red-salmon fingerlings migrating to the ocean 
were first seen in abundance at the Karluk weir on June 1. The 
migration continued for about 2 weeks and appeared to be normal 
in size. Samples of the fingerlings were taken to determine the age 
composition of the migrant run, and the average length of the indi- 
viduals in each age arene The 1939 migrants were of average size 
and were considerably 1 arger than the 1937 and 1938 migrants. 
Between May 21 and September 23, 666,004 adult red salmon were 
counted as they passed through the weir, and it was estimated that 
after the removal of the weir on September 23, 40,000 additional red 
salmon ascended the river. Only twice before, over a period of 19 
years, has the escapement been less than in 1939. However, condi- 
tions on the spawning grounds appeared to be favorable, and a fair 
to good return is anticipated, despite the relatively small size of the 
escapement. 
The number of pink salmon passing through the Karluk weir was 
31,944. ‘This is the largest odd-year escapement of pink salmon since 
1933, and it is evident that the 2-week cessation of commercial fishing 
in the Karluk area, between July 24 and August 5, was beneficial. 
Racial study. —Tt has long been recognized that the run of adult 
red salmon to the Karluk River is characteristically divided into 
2 parts. The first peak of abundance occurs in June, and the second 
