BUREAU OF FISHERIES 89 



are provinir of practical value in the cultivation of the native Olym- 

 pia oyster. 



Experiments on the artificial cultivation of fresh water mussels, 

 which ]irovide the raw material for the American pearl-button in- 

 dustry, have been prosecuted with success. Large quantities of the 

 valuable species have been grown in artificial raceways at the Bu- 

 reau's station at Fort Worth, Tex., and methods for feeding mussels 

 have been devised, which materially accelerate their normal growth. 



POLLUTION STUDIES 



Efforts during the past several years to stock depleted streams of 

 the Mississippi drainage with fresh water mussels, produced by 

 artificial propagation, have failed because of the increased pollu- 

 tion in these waters ifrom industrial and domestic wastes and silt 

 eroded from the surface of the land. The presence of great quan- 

 tities of silt, which is rapidly increasing, moreover, jeopardizes the 

 continued existence of all of the more valuable forms of aquatic 

 life throughout the drainage. This problem has been given much 

 study from the point of view of determining definitely the menace 

 of silt pollution and the extent of polluted waters in the hope of 

 finding areas suitable for restocking with the valuable mussel 

 species. 



A careful investigation of the physiological effects of toxic sub- 

 stances found as pollutants in rivers of the Middle West has been 

 continued in cooperation with the University of Missouri. Studies 

 on the effects of arsenic, cyanide, and various heavy metals and 

 acid mine wastes have demonstrated the disastrous effects upon 

 aquatic life of these substances in the streams. During the fall a 

 detailed investigation in the field, supported by laboratory studies, 

 on the effects of mine pollution in the Coeur d'Alene district of 

 Idaho, demonstrated the serious effects upon fish and invertebrate 

 aquatic life of washings from stamp mills and from mine drainage, 

 and recommendations were offered to the State outlining means of 

 overcoming this menace to an important natural resource. 



ALASKA FISHERIES SERVICE 



ADMINISTKATION OF FISHERY LAWS AND REGULATIONS 



The general abundance of the fisheries of Alaska in 1932 may be 

 attributed primarily to the conservation program that has been car- 

 ried on since the law of June 6, 1924, gave the Secretary of Com- 

 merce broad powers to control commercial fishing. Careful surveys 

 of the fisheries were made throughout the season, and the regulations 

 were modified to meet changing conditions. The Commissioner of 

 Fisheries spent several weeks in Alaska for personal observation of 

 the salmon fisheries, which constitute the Territory's most important 

 economic resource. 



Revised fishery regulations were issued on December 20, 1932, and 

 became effective January 1, 1933. The restrictions in several regions 

 were relaxed by extending the fishing season or by opening closed 

 waters to limited operations. Trap fishing was further curtailed 



