156 REPORT OF THE SECRETARY OF COMMERCE 
At the beginning of the fiscal year 1989 Congress made funds 
available to the Bureau of Fisheries for a large-scale study of the 
factors that control the salmon populations of Bristol Bay in order 
that a sound and comprehensive system of management might be 
applied. With the cooperation of the Coast Guard, extensive hydro- 
eraphic observations were conducted in the summers of 1938 and 
1939. Biological observations were made also to discover the school- | 
ing habits of the fish far offshore, the abundance and distribution 
of food animals, and the migratory habits of the salmon in approach- 
ing the coast from these offshore feeding grounds. Correlated with 
these oceanographic studies, investigations of the life cycle of the 
salmon in the five major watersheds of this area are under way. 
These include detailed population studies of the spawning runs, sur- 
veys of spawning grounds, and measurement of the mortality of the 
young in fresh water. This investigation is planned to cover a 
5-year period, or the normal life cycle of the red salmon. 
Studies of the returns to be expected from any given escapements 
of spawning salmon were continued in the Karluk watershed. Fur- 
ther evidence was secured that variations in the ratio of returns to 
escapement are mainly due to conditions existing in the fresh-water 
environment. To determine the role of the predatory Dolly Varden 
trout in reducing the number of young red salmon, the migratory 
habits and biological characteristics of the populations of trout have 
been investigated through the tagging of large numbers of these fish. 
In areas where the migration routes of salmon pass through com- 
mercial fishing areas to a number of different streams, the 50-per- 
cent escapement required by law cannot be assured unless the exact 
routes of the salmon and their distribution on the spawning grounds 
are determined. Tagging experiments were conducted during the 
1938 and 1939 seasons to trace the migration routes of pink salmon 
passing through Lewer Chatham Strait. The two experiments will 
provide information covering the routes of migration of both the odd- 
and even-year pink salmon runs. 
The usual population studies to determine the size of the pink- 
salmon runs and the proportion of males and females were conducted 
at Little Port Walter. The construction of a permanent dam and 
counting weir, which was in operation during the 1939 season, now 
permits an accurate count of seaward-migrating young as well as 
upstream migrants, so that the returns from a known number of 
spawners may be determined with greater accuracy than heretofore. 
Changes in the time of appearance of the pink salmon runs are being 
closely analyzed so that any necessary curtailment of the fishery may 
be effected in time to allow an adequate escapement to the spawning 
grounds. 
As an aid to rebuilding the runs of coho salmon in Puget Sound, 
studies have been carried on over a period of years to determine the 
age at which hatchery-reared fry may be released most advantage- 
ously. A series of marking experiments for this purpose was con- 
cluded in 1938. Biological studies of the size and age composition 
of the population were made by taking samples of the commercial 
catch and of the fish on the spawning grounds. 
Studies of the age composition of the herring population of south- 
eastern Alaska were responsible for demonstrating that this stock 
