BUBEAU OF FISHERIES 93 



quarterboat 8Jf8. These methods permit more detailed and more 

 rapid determinations of the effects of the various stream pollutants 

 not only on fish but on the basic fish-food organisms as well under 

 conditions existing in the polluted waters. A systematic study of 

 the effects of effluents of various industrial operations and of munici- 

 pal sewage is being made with a view to supplying standardized data 

 concerning both the actual and relative toxicity of these effluents to 

 fish and fish food. As a part of this work, a comprehensive study of 

 the toxicity of ammonia, which is one of the chief break-down prod- 

 ucts of municipal sewage and one of the principal effluents from gas 

 factories, to fish and fish- food organisms under stream conditions, has 

 been completed. 



It has been shown by some of the work now completed that certain 

 types of industrial and municipal wastes can be utilized to increase 

 the plankton content of natural waters when these wastes are prop- 

 erly diluted and separated from noxious and toxic wastes. As a basis 

 for plans to conserve these substances, which can be utilized in the 

 production of fish food in inland waters, biological assays of the 

 fish-food values of various wastes are in progress. 



Long-time experiments dealing with the effects of erosion silt on 

 fresh-water mussels have been completed at the Fort Worth sub- 

 station. These experiments have definitely established the fact that 

 even very small quantities of erosion silt are highly detrimental 

 or fatal to the principal commercial species of fresh-water mussels. 

 Other long-time experiments on the survival and growth of fresh- 

 water mussels under conditions of stream pollution are in progress 

 at Fort Worth. 



ALASKA FISHEBIES SERVICE 



ADMINISTRATION OF FISHERY LAWS AND REGULATIONS 



In general, the Bureau continued the program followed in pre- 

 vious years for the conservation of the fisheries of Alaska, although 

 reduced funds made it necessarj^ to curtail some phases of the 

 work. The Commissioner of Fisheries visited all important fishing 

 districts in the summer and held hearings at about 20 places, giving 

 all interested persons full opportunity to express their views. 



Eestrictions on commercial fishing were modified during the sea- 

 son as changing conditions warranted, and revised regulations were 

 issued on December 21, 1933, to be effective in 1934. Except for the 

 closure of additional trap sites, most of the changes relaxed existing 

 prohibitions, the purpose being to spread employment wherever 

 possible without impairing the future supply of fish. 



A patrol of the fishing grounds was maintained to assure enforce- 

 ment of the laws and regulations. One hundred and thirty-one 

 stream guards and special employees were engaged for varying 

 periods in this protective work, under the direction of 12 regular 

 employees of the Bureau. Many of these guards furnished their 

 own launches and were stationed at the mouths of salmon streams 

 to prevent poaching in closed areas. Fourteen Bureau vessels, 

 manned by 53 persons, and 2 chartered vessels with 2 men patrolled 

 the larger bodies of water. 



108111—35 2 



