BUREAU OF FISHERIES 93 



Research activities are about equally divided among three im- 

 portant fields. These are (1) aquicultural investigations including 

 stutlies on the improvement of hatchery technique for both cold and 

 warm water fishes and the planning of rational stocking policies in 

 interior waters, (2) commercial fishery investigations concerned with 

 the changes in abundance of the food fishes of the coastal areas and 

 the Great Lakes, the detection of overfishing, and the correi tion of 

 abuses in the commercial fisheries, and (3) shell-fishery investigations 

 directed toward imi)roving the quality of oysters, increasing produc- 

 tion by cultural methods and combating oyster pests. 



The technical staff of the Division of Scientific Inquiry numbers 

 45 trained experts, with perhaps an equal number of temporary 

 assistants at some times of the year, but the i)roblems of the fisheries 

 are as numerous as the species that are exploited. Some 30 important 

 food and game fishes are the subjects of continuing research, but to 

 give adequate attention to the fisheries in all sections of the United 

 States — coastal, interior, and in Alaska — would require double the 

 number of present investigators. 



AQUICULTURAL INVESTIGATIONS 



The problems of the fresh-water fisheries throughout the country 

 at present are concerned chiefly with increasing hatchery output and 

 properly stocking interior waters. In carrying out the latter pro- 

 gram, the discovery of suitable natural conditions by means of stream 

 surveys, the conditioning of streams to improve their fish carrying 

 capacity, and the control of stream pollution are vital to its success. 



Pond-fish culture. — Investigations in pond-fish culture were con- 

 ducted during the past year at the Natchitoches (La.) fish hatchery. 

 These investigations were designed primarily to throw light on the 

 problems which have arisen in connection with pond culture in the 

 Southern States where conditions in many respects are quite different 

 from those found in hatcheries in the North. Experiments during 

 1934, designed primarily to furnish a comparison of the value of 

 difl'erent fertilizers show that cottonseed meal and other fertilizers 

 are beneficial in producing a large crop of forage organisms on which 

 the fish feed, but that food production alone is not directly correlated 

 with fish production. In heavily fertilized ponds large numbers of 

 small fish may be produced for early distribution, but additional 

 forage food is required to carry the bass through the summer until 

 October or November. 



Trout culture. — Trout cultural investigations have been conducted 

 at the experimental hatcheries located at Pittsford, Vt., and Leetown, 

 W. Va. Here experiments were designed to determine the most 

 economical ration for the feeding of both fingerling and older trout. 

 Detailed observations were made on the food requirements of fish 

 of the same species at different ages and of the different species of 

 trout as a guide to more economical general hatchery practices. Selec- 

 tive breeding experiments have also been conducted at these two 

 stations to secure a superior strain from the point of view of growth, 

 ^g^ production, and disease resistance. Future brood stock was se- 

 lected from fish of known lineage for propagation of future supplies. 



Fish nutrition. — At the United States Fishery Station, Cortland, 

 N. Y., cooperative investigations of fundamental problems of trout 



