BUREAU OF FISHERIES XXIII 



of the various runs be available. The bureau's investigators con- 

 tinued biological observations on these subjects and on the red 

 salmon in Bristol Bay and the Karluk, Chignik, and Copper Rivers 

 in Alaska. A similar investigation was carried on with respect to 

 the pink salmon in southeastern Alaska. An additional section of 

 the analysis of the statistics of the Alaska salmon fisheries covering 

 the Prince William Sound area and the Copper and Bering Rivers 

 has been submitted for publication. 



Further knowledge of the life history of the Alaska herring dem- 

 onstrates the racial segregation of the stock and points out the causes 

 of fluctuations in abundance from year to year. Again the prin- 

 cipal of dominant year classes apply as in other fisheries and indicate 

 the importance of protecting the supply during periods when natural 

 reproduction falls below normal. 



During 1931 an investigation of the sockeye salmon fishery in 

 Puget Sound was undertaken to study the annual changes in abun- 

 dance of the runs as shown by statistics of the past seasons and to 

 identify distinct races taking part in these runs, if such exist, so 

 that protection may be given to the elements of population that 

 apparently are suffering depletion. Such information will be of 

 great value in protecting the fishery in the event that the interna- 

 tional treaty under consideration is finally ratified. 



FISH-SCREEN AND FISH-LADDER INVESTIGATIONS 



After extensive trials with various types of fish screens, including 

 the electric, the bureau's investigators have concluded that in order 

 to protect downstream migrating salmon and other fishes from 

 destruction in irrigation projects the revolving mechanical screen is 

 preferable. Under some circumstances success has been had with 

 the electric screen; but public opinion frequently is opposed to its 

 use, and no large-scale program of future installation of this type 

 is contemplated. The bureau has cooperated with the States of 

 Washington, Idaho, and Maine in preparing designs and advice 

 for the installation of improved types of fish ladders on various 

 large-scale hydroelectric or irrigation projects. 



AQUICULTURAL INVESTIGATIONS 



A considerable amount of attention is given to problems of interest 

 to the angler, inasmuch as they concern the food and game fishes 

 of interior fresh waters and their culture, distribution, and planting 

 in depleted or formerly barren areas. Facilities for investigations 

 in the interest of fish culture were materially increased during the 

 year by the construction of a new experimental hatchery at Leetown, 

 W. Va. At this station facilities have been provided for detailed 

 laboratory studies on the nutrition of fish and on fish diseases. The 

 hatchery troughs were stocked fully with rainbow, brook, and brown 

 trout eggs and at the close of the year were filled with vigorous 

 and rapidly growing fingerlings. Although funds did not permit 

 the full development of the station, a bass pond was constructed and 

 outdoor pools of circular type are being tested on a considerable 

 scale and are found to be particularly successful for the rearing 

 of trout. 



