PROGRESS IN BIOLOGICAL INQUIRIES, 1938 37 
total return from each season’s spawning brood, and the selective 
effects of the commercial fishery may be determined. 
Marine studies—The sockeye salmon, after migrating seaward, 
spend 2 or 3 years in the ocean and then return to fresh water to 
spawn. During this period they make over 98 percent of their 
growth in weight. Hence, environmental factors affecting the fish 
during their stay in salt water have a most important part in deter- 
mining the condition and quality of the mature fish. 
The United States Coast Guard very generously cooperated with 
the investigation by furnishing one of their large cutters, the Red- 
wing, for the purpose of conducting an oceanographic survey of the 
waters of Bristol Bay and the contiguous waters in which salmon live 
during their ocean sojourn. 
The program of oceanographic studies followed the general meth- 
ods used by Dr. T. G. Thompson, Director of the Oceanographic 
Laboratories at the University of Washington, who has been making 
oceanographic studies of the North Pacific Ocean for a number of 
years. In this way the data will be in proper form for comparison 
with the results of the general survey. 
During the season the entire area of Bristol Bay proper, compris- 
ing over 10,000 square miles, was crossed and recrossed and samples 
were collected at 164 stations. The oxygen and salinity content of 
the water were determined and temperature data collected for the 
purpose of calculating the direction and force of the ocean currents. 
As a corollary to these studies current meters were operated at various 
depths and data were collected on the type of bottom and the depth 
of water at each station. Plankton samples were collected to deter- 
mine the type and abundance of food present for the fish. 
The oceanographic surveys are to be continued and the migration 
routes of the fish are to be determined by extensive marking, tagging, 
and sampling programs. These data will also furnish information 
on the fluctuations in ocean mortality. 
KARLUK RIVER RED SALMON 
The investigation to determine the extent and causes of the 
fluctuations in the size of red salmon runs in Karluk River, Alaska, 
was continued in 1938 by J. T. Barnaby and Allan C. DeLacy. Field 
work was carried on from early April until the end of September. 
Population studies —The commercial catch of Karluk red salmon 
was sampled throughout the season to discover marked fish return- 
ing from marking experiments carried out in previous years. Dur- 
ing the season 305,283 salmon were examined and 1,481 marked fish 
were found. The purpose of these experiments is to determine the 
mortality of the fish during their stay in the ocean. The results to 
date indicate that ocean mortality is fairly constant and that the 
variations in the ratio of return to escapement are mainly due to 
fluctuations in the environmental conditions affecting the fish during 
their stay in fresh water. The returns of marked fish during the 
past season were mainly from the experiments of 1936, in which year 
26,700 fingerlings were marked by excision of the adipose and right 
ventral fins and 26,700 by excision of the adipose and both ventrals. 
Thus, in addition to the basic information desired, these experiments 
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