120 REPORT OF THE SECRETARY OP COMMERCE 



The Disease Service continued to assist in the diagnosis of hatchery 

 disease by examining preserved specimens sent to the Seattle and 

 Washington laboratories. This service is extended to Federal, State, 

 and private fish culturists. 



POLLUTION INVESTIGATIONS 



Every State and every major river system have now been included 

 in the stream-pollution studies conducted from headquarters at Co- 

 lumbia, Mo. Over 150 new localities were investigated during the 

 year and observations were co]itinued at approximately 70 old sta- 

 tions. Data collected from these field and laboratory studies are being 

 applied to the solution of practical fisheries problems. Forty-three 

 major cases of stream pollution were investigated by the staff during 

 the 3^ear and reports were pre]:)ared for the guidance of officials con- 

 cerned. In addition, the staff has aided in the solution of some 

 200 lesser problems. Many manufacturers have cooperated to a grati- 

 fying degree in applying the findings of the staff. 

 " Detailed surveys were made of several artificial impoundments of 

 water, and practical applications of these studies have been made in 

 connection with the stocking programs of various Western streams 

 on which in^poundments have been built or are contemplated. 



SHELLFISH INVESTIGATIONS 



Oysters continue to hold second place in value among all fishery 

 products. The industry is troubled, however, by the increasing deple- 

 tion of the natural beds, the destruction of valuable bottoms by pollu- 

 tion, and the losses caused by natural enemies. 



In the New England area the principal problems are those of obtain- 

 ing an adequate set of larval oysters and of protecting the beds from 

 starfish. Information on the expected time of spawning and setting 

 was distributed at weekly intervals during both the 1937 and 1938 

 seasons through the cooperation of the Connecticut Shellfisheries Com- 

 mission. This information was based on systematic observations of 

 water temperatures and the condition of oysters at selected points in 

 Long Island Sound. It is hoped to extend this service to other areas 

 in the near future. 



The destruction of most of the early season set of oysters in 1937 by 

 starfish demonstrates the importance of studies for their control which 

 were carried on intensively from the Milford, Conn., laboratory dur- 

 ing the winter and spring. A chemical method of control was applied 

 under both field and laboratory conditions and its effectiveness in 

 destroying starfish was established. Careful tests have revealed no 

 injury to oysters. 



Ecological observations were made by the staff during the year at 

 other points on Long Island Sound and in the inshore waters of 

 Virginia, North Carolina, Alabama, and Florida. These observations 

 have guided State authorities and private oyster growers in trans- 

 planting seed and planting material for the collection of set. Plans 

 were also prepared for the rehabilitation of several depleted areas. 



Studies under way from the new marine laboratory at Pensacola, 

 Fla., include surveys of the condition of local oyster beds and the 

 collection of hydrographic data and planltton samples at selected 

 points. 



