BUREAr OF FISHERIES XVII 



regulatory recommendations, investigations are conducted as a means 

 of increasing the output of the hatcheries and of more wisely directing 

 the planting and stocldng system. Studies have also been conducted 

 on the problem of increasing the productivity of natural water areas 

 and on fish farming in small lakes and ponds. 



Major projects of research are conducted in each of the geographical 

 sections and coasts of the United States and the more important 

 interior waters, covering some 28 important commercial and game 

 fishes, as well as studies of organisms related to these species either as 

 food or as enemies. 



Outstanding progress has been made in the aquicultural investi- 

 gations that are concerned primarily with increasing the output of 

 hatcheries and the stocking of interior waters with food and game 

 fishes. Of more direct benefit to the commercial fisheries are the 

 investigations on shellfish culture, particularly in the farming of 

 oyster l)ottoms and in the investigation of the commercial fisheries 

 of the North Atlantic. A most direct method of conservation of the 

 salmon of the Pacific Coast States is preventing the destruction of 

 millions of young salmon entering irrigating canals while migrating 

 to the sea from the spawning places in the headwaters of the rivers. 

 The bureau's installations of experimental screens at the mouths of 

 irrigating ditches are proving particularly effective. 



AQUICULTVR.\L lXV?:STIGATIOXS 



The division's fresh-water investigations in aquiculture are included 

 under four headings: Experimental trout culture, experimental bass 

 culture in ponds, ex])eiimental fish cidture in the l'i)per Mississippi 

 River Wild Life and Fish Kefuge, and studies on the pathology of 

 hatchery fish. Several years' experiments in the use of various sub- 

 stitutes for fresh jnent in the diet of biook ti'out have culminatcMl in 

 the adoption of an ideal ration that includes dry meals with the regu- 

 lation beef liver and beef heart diet in sufficient quantities to reduce 

 the total cost of feeding by about 50 per cent. These perfected rations 

 not only produce excellent growth in the fry and fingerlings but reduce 

 mortality to a minimum and ])ermit the holding of trout at hatcheries 

 imtil greater si/e is reached before ])lanting. Experiments on selec- 

 tive breeding are also under way that give ])romise of producing a 

 superior strain of brood stock that is rapid growing, disease resisting, 

 and al)Ove the average in egg production. 



At the bureau's pond-culture station, experiments on the rearing 

 of black bass have been e(|ually successful. Better and more efficient 

 methods have been devised for propagating and rearing the warm- 

 water game fishes, such as the large and smallmouth black bass, the 

 white and black crappie, and the bluegill sunfish. By the proper 

 use of minnows as forage fish and by the fertilizing of ponds with 

 commercial and chemical fertilizers, the bureau has produced as high 

 as 11,500 fingerhng bass per acre, and one of its ponds has averaged 

 8,500 per acre for three years. 



In the I'pper Mississipj)i Wild Life and Fish Refuge a number of 

 sloughs and ponds in the overflowed lowlands of the river valley 

 have been prepared for intensive fish juoduction, and detailed linino- 

 iogical observations on the abundance of fish and the character of 

 tish food available in the area have been made. One of the most 



