XXIV ItEPOKT TO THE SECEETAIiY OF COMMEKCE 



FISH SCREEX AND FISH LADDER IN\T2STIGATION8 



The investigational work pertaining to the conservation of fish 

 by means of screens and ladders has been continued without in- 

 terruption. Field experiments with the electric screen have led to 

 the adoption of simplified and improved apparatus. The highly 

 satisfactory action of the electric screen in preventing upstream 

 migrants from entering tail race waters was maintained during the 

 past season. However, its effectiveness will never be 100 per cent, 

 and there is a tendency on the part of the public to be apprehensive 

 of the electric screen. On all new projects and wherever possible 

 elsewhere the recommendation of the bureau is for the mechanical, 

 revolving screen — a device which is unpatented and one which long 

 use has proved to be entirely effective and reliable. The bureau 

 continues to operate with success its electric screens in the Yakima 

 country, where it is now impracticable to install mechanical screens. 

 A development of the season's work was the discovery of the im- 

 provement that can be effected in leading migrating fish to by-pass 

 channels by the use of lights. A survey has been made of fish-screen 

 problems in Montana, and the bureau now has under construction 

 a mechanical screen for the Jocko Canal and is preparing detailed 

 plans and specifications for a mechanical screen (the largest ever 

 constructed) on the Sun River Canal of the United States Reclama- 

 tion Service. 



In the fall of 1930 the bureau designed and constructed two con- 

 crete fish ladders on Government projects, these being located at 

 Sprague River Dam in Oregon and at Wapato Dam in Washington. 

 Both structures are similar in design to the successful ladder built 

 by the bureau at Sunnyside Dam. During the winter the fish ladder 

 reciuirements of the State of Maine were examined and reported 

 on. In Idaho, special fishway problems received attention. 



Considerable work has been done in connection with hydroelectric 

 developments proposed or now under construction on streams sup- 

 porting migratory fish. Applications for power licenses have been 

 studied, field examinations made, and the proper fish-protective de- 

 vices specified. Miscellaneous activities of the investigation have 

 included engineering services in the preparation of designs for the 

 water supply at the proposed new Butte Creek hatchery and for the 

 new pumping equipment and distribution system at Clackamas 

 hatchery. 



AQUICULtURAL INVESTIGATIONS 



Facilities for investigations in the interest of fish culture were 

 materially increased during the fiscal year by improvements at the 

 Fairport (Iowa) stati(m, where pond facilities weie nearly doubled. 

 This station has become a i)rime factor in the bureau's fisli-cultural 

 activities, for the principles of black-liass culture which have been 

 developed here are being generally adopted throughout tlie country 

 at large wherever conditions are suitable. The output of fingerling 

 bass which resulted as a by-product of the experimental work was of 

 material aid in filling requests for fish for planting. Similar inves- 

 tigations to adapt the new principles to local conditions have been 

 undertaken at several of the fish-cultural stations, and studies are 



