322 REPORT OF THE SECRETARY OF THE INTERIOR 
35,000 square miles consisted of regular samples of seaward migrant 
fingerlings taken at five points selected for the purpose. Finger- 
lings were marked for future identification and released wherever 
they were available in sufficient numbers, and scale samples, body 
measurements, weights, and information on sex proportions were 
obtained from each of the principal rivers during the commercial 
fishing season. Investigations at sea included experimental fishing 
and tagging to, determine the feeding grounds and migratory routes 
followed by the adult salmon as they make their way in to the rivers 
to spawh. 
Investigation of the decline in productivity of the Karluk River 
watershed has revealed that, while the mortality of salmon during 
the period of life in the sea is remarkably constant, great variations 
in the percentage of mortality in fresh water are to be expected. 
These variations are related to changing environmental conditions 
and to cycles in the fertility of the lake and the abundance of food 
organisms. A report on the phases of this investigation that are 
now completed has been prepared for publication. 
The existence in the Karluk system of at least two separate popula- 
tions of the Dolly Varden trout, which prey to some extent on red 
salmon, has been demonstrated by tagging. Since one of the popula- 
tions is resident within the lake and the other migrates annually to 
and from the ocean, control measures, if found necessary, would differ 
for the two groups. 
Improved facilities have now been provided for the study of the 
pink salmon, which is by far the most abundant species of salmon in 
Alaska and hence an important source of food. Because of the short 
life cycle of this species (2 years) it is possible to build up or decimate 
a population of pink salmon within a short time, hence the need for 
continued watchfulness. A combination dam and counting weir is 
now in operation at Little Port Walter, making possible observations 
that will be used to compute the percentage of mortality in both fresh 
and salt water. A permanent biological field station has also been 
established so that biological observations on the survival of the | 
broods may be made throughout the year, permitting more accurate | 
predictions as to the size of the annual runs. 
Throughout the year the collection, tabulation, and analysis of the 
daily catch records of the various types of fishing gear operated by 
the salmon fishery of Alaska were continued, contributing to an invalu- 
able permanent record of the fishery throughout the Territory. In- 
dices of abundance derived from these data are an important basis for | 
recommendations for changes in the fishing regulations. 
The collection of statistical and biological data on the Alaska herring 
fishery has been continued with a view to safeguarding the supply, 

