200 U. S. BUREAU OF FISHERIES 



The present state of the bureau's biological investigations may be 

 shown by the following list of projects continued and completed. 

 The titles given are not descriptive but merely indicate the field in 

 which work is conducted. Details of fhe investigations may be 

 gained from the following pages. 



Projects continued : 

 Cod. 



Mackerel. 

 Smelts. 

 Larval fishes. 

 Texas shore fisheries. 

 Alaska salmon. 

 Columbia River salmon. 

 Alaska herring. 

 Trout culture. 

 Pond culture. 

 Pathology of fishes. 

 Wisconsin lakes. 

 Oysters. 

 Clams. 



Projects continued — Continued. 



Scallops. 



Mussels. 



Terrapin. 



Summer laboratory work by vol- 

 untary vporkers. 

 Projects completed : 



Oceanography of the Gulf of 

 Maine. 



Food habits of sharks. 



Coregonidffi of Great Lakes. 



Pollution in upper Mississippi. 



Keokuk Dam and fishes of upper 

 Mississippi. 



Chesapeake Bay fishes. 



During the past year several lines of investigation have shown 

 unusual success in the application of scientific principles to practical 

 problems. 



The salmon investigations have continued to yield detailed informa- 

 tion concerning the routes of migration and the success of spawning 

 escapement in the various localities, which has been used as the basis 

 for modifying or improving the regulations of the fishery in the 

 interest of conservation. 



The investigations on the diseases of fish are continuing to prove 

 their practical importance. The causes of diseases that annually 

 have taken heavy toll of the output of many hatcheries throughout 

 the country are yielding to continued research, and the pathologist 

 has rendered valuable aid in advising hatchery superintendents in 

 the prevention of devastating epidemics. 



Investigations of the marine fisheries of the Atlantic coast are 

 showing extremely promising results, especially in the case of the 

 mackerel fishery, where the causes for extreme variation in abundance 

 have been discovered in the great success or almost complete failure of 

 spawning and survival in various years. Although these factors 

 appear to be beyond the control of man, the prediction of their occur- 

 rence (which, as a result of these studies, appears to be possible) will 

 be of great economic benefit to the industry. 



Another outstanding accomplishment of the year was the perfec- 

 tion of methods of artificial propagation of the fresh-water mussel, 

 a shellfish that yields the raw material for millions of dollars worth 

 of pearl buttons manufactured annually from the shells. Natural 

 processes of propagation are extremely wasteful, and until now arti- 

 ficial methods have been almost equally hazardous and doubtful of 

 results. The new process of cultivation, in which the parasitic stage 

 has been eliminated entirely, makes possible the production of com- 

 mercially significant quantities of young mussels gTown to a stage at 

 which survival is fairly certain. Moreover, the process can be con- 

 trolled, a desirable stock can be selected for spawning, and the 

 progeny can be planted in the most favorable localities, either on 

 j)ublic grounds or on privately controlled beds, making mussel farm- 



