BUREAU OF FISHERIES 87 



instinct similar to that of the red salmon returning for spawning 

 with few exceptions to the streams in which the fish were hatched. 

 The life cycle has definitely been establised as 2 years and further 

 investigations regarding the biological factors responsible for fluctua- 

 tions in time of appearance and abundance of the runs have pro- 

 gressed sufficiently to have practical application in devising regula- 

 tions for the upbuilding and maintenance of the supply. 



As a means of ascertaining more effectively the segregation of 

 independent races of herring in Alaska, each of which is subject to 

 ■overfishing without affecting neighboring supplies, a new method 

 of tagging has been i)erfected for a study of their migrations. The 

 method isunique in fisheries science inasmuch as electromagnets are 

 lutilized to recover metal tags in the factories in the process of manu- 

 facturing fish meal. Further studies of fluctuations in abundance 

 from year to year demonstrate the effect of year class dominance as 

 a cause of changing yields and indicate the necessity for regulation 

 of the fishery in times of reduced supplies. 



A study of the sockeye-salmon fishery in Puget Sound, under- 

 taken during 1931, has shown that severe overfishing virtually 

 destroys the big runs of salmon that occur every 4 years in the 

 Frazier River system. Since this river supports the most valuable 

 salmon fisheries in the State of Washington, efforts will be made to 

 regulate the fishery so as to restore it to its former abundance. 



FISH SCREEN AND LADDER IN\T:STIGATI0NS 



Investigations of methods of conserving the runs of anadromous 

 fish on the Pacific coast by means of screens and ladders have been 

 completed. Revolving mechanical screens have been found to be 

 most effective and under certain circumstances electric screens have 

 also proved their efficiency. Recommendations and perfected designs 

 have been made for a large number of irrigation works in Washing- 

 ton, Oregon, Idaho, Utah, and Nevada, and recommendations for 

 fish protective works at hydroelectric developments have been made 

 to the Federal Power Commission. 



AQUICUL'IXHAL INVESTIGATIONS 



Practical results of the Bureau's investigations in the interest of 

 improved fish-cultural practices have been evidenced by a sustained 

 output of large and vigorous fish from the Bureau's many hatcheries 

 in the face of reduced appropriations. Studies conducted at the 

 three experimental hatcheries have shown the feasibility of extensive 

 utilization of cheaper ingredients in the diet of trout and the utility 

 of fertilizers and forage fish in the economical production of bass 

 and other warm-water fish. Trout breeding experiments have like- 

 wise demonstrated the superiority of selected strains of brood fish 

 over wild stock in increased egg production, in more rapid growth, 

 and in resistance to disease. It has been shown that hatchery pro- 

 duction can be increased four times by doubling the rate of growth 

 and the number of progeny from a single pair through selection of 

 the brood stock. Progress has been made in solving the problems 



