116 REPORT OF THE SECRETARY OF COIMMERCE 



North PacifiG and Alaska fshery^ investigations. — Commercial fish- 

 ery investigations in northern Pacific waters are concerned with rec- 

 ommending measures for the management and conservation of the 

 salmon runs in the rivers of the Northwestern Coastal States and with 

 maintaining at a productive level the salmon and herring fisheries of 

 Alaska, over which the Federal Government has jurisdiction. 



Rehabilitation of the Columbia River's $10,000,000 salmon industry 

 is believed to depend in large measure upon the restoration of formerly 

 productive spawning areas which are now unavailable or unsuitable. 

 Approximately 2,500 miles of stream have been surveyed for the pur- 

 pose of discovering additional spawning grounds that may be restored 

 to use and of locating obstructions to upstream migrants and hazards 

 to seaward migrating fingerlings, such as unscreened irrigation 

 ditches. Data for 2,300 miles of stream which were tabulated during 

 the winter showed a total of 418 dams, of which 288 are temporary 

 and 104 are permanent. Five hundred ninety-five diversions were 

 discovered, 563 of which are used for irrigation. On the basis of 

 surveys covering north central, south central, and southeastern Wash- 

 ington, it is estimated that about 55 percent of the streams surveyed 

 provide suitable spawning areas, but about half of this total is un- 

 available to fish at low water. 



In Alaska, Government regulation of the commercial salmon catch 

 is designed to allow a sufficient number of spawners to escape the fish- 

 ery to maintain the runs of future years. The effectiveness of such 

 regulations depends upon knowledge of the returns that may be 

 expected from a given spawning escapement. Since past observations 

 have established the fact that the ratio of spawning adults to returns 

 several years later varies considerably, studies of the conditions which 

 govern such fluctuations are of paramount importance. Continuing 

 programs of research are therefore conducted on red salmon at Karluk 

 River and on pink salmon at Little Port Walter in southeastern 

 Alaska. 



Additional evidence was secured during the year indicating that 

 better returns are obtained from red salmon fingerlings that remain 

 in fresh water until their third or fourth year than from those that 

 migrate at an earlier age. It is therefore clear that the discovery of 

 means to improve growth and survival of the young in fresh water 

 will have a definite effect on the size of the runs. Major attention 

 was given during the summers of 1937 and 1938 to an investigation 

 of the effect of predatory Dolly Varden trout in reducing the numbers 

 of young salmon. Little information being available about the migra- 

 tions, growth rates, and age of this species, a series of marking experi- 

 ments was carried out to supply such knowledge. Field observations 

 throughout the spawning area showed that the heaviest toll is taken 

 during the spring, at the time the young salmon are entering the lake 

 from the spawning streams. 



The long-term study of the pink salmon populations of southeastern 

 Alaska deals chiefly with measuring the success of spawning in the 

 streams each year, and with discovering the effect of various natural 

 conditions on the survival of the young. Because the pink salmon^ 

 unlike the red, has a 2-year life cycle, the failure of 1 year's brood has 

 serious effects on the fishery 2 years later. Continuous observations 

 are therefore necessary in order to foresee such poor years and regu- 



