396 r. 5. BUEZAr of fishxeies 



Mississippi River -with reference to the effects of pollutant effluents 

 on that stream has been made from Cairo. Ill,, to Grand Rapids, 

 Minn. The Misissippi River was chosen as presenting typical prob- 

 lems of a major stream receiving a variety of pollution effluents. 

 Studies on other streams in different States have been made with 

 reference to specific pollution problems as well. The effluents from 

 some 15 types of industries representing over SO industrial plants 

 have been studied both in the field and in the laboratory. In addi- 

 ti(m, mine wastes, particularly from coal. lead, copper, iron, zinc, 

 and arsenic mines, have been analyzed and assayed as pollutants. 

 Oil pollution of fresh water has been given detailed attention in 

 the States of Kansas. Oklahoma. Texas, and Louisiana, particularly 

 during the months of October to January, inclusive: and these 

 findings correlated with oil pollution already noted in our field 

 work elsewhere. 



Municipal effluents and garbage pollutants were given specific at- 

 tention in the St. Louis. Davenport, and [Minneapolis- St. Paul areas. 

 During Xovember a field party made an extensive study of the best 

 sugar industry effluents in Xebraska. Colorado, and Kansas, and other 

 field parties have studied the sulphur pollution in Louisiana, lime- 

 stone wastes in Indiana, natural alkali ]X)llution in Xorth Dakota 

 and Montana. All of this pollution work has had as a major objec- 

 tive the determination of: (1) The effects of these substances on fish 

 life, particularly the major types of fresh-water fishes; (2) the effects 

 of these substances on fish food, specifically those insects, crustaceans, 

 and mollusks, which constitute a large part of the food of fresh- 

 water fishes: and on the aquatic bacterial flora, particularly those 

 forms concerned with the utilization of organic wastes and those 

 forms which are part of the food chain series in fresh waters: and 

 (3) the chemical and physical balances of the various substances 

 occurring naturally in many of the fresh-water streams of the United 

 States. 



Yrom these studies standards of water purity have been deter- 

 mined for fish life and measurements of pollution hazards made 

 which can be applied quite generally to the fresh-water streams of 

 the United States. Xew and practical methods for measurement of 

 pollution hazards, relative toxicity, and importance of pollution efflu- 

 ents have been perfected in the course of this work. The work com- 

 pleted shows definitely the size of the task involved and the needs for 

 continuation of studies along these lines. 



P>:'WZE DAM T ^TTFi; AND OTHKH DIPOUXDED WATEES 



.StU'iies of power dam lakes and other impounded waters have been 

 carried forward, particularly in connection with the Tennessee Valley 

 AuthoritT projects in the Xorris Dam area and in connection with 

 the Fort" Peck Dam which is being constructed in Montana. As a 

 result of these studies, recommendations have been made to the Ten- 

 nessee Valley Authority, and certain special lateral lakes are now 

 being established in the Xorris Dam area to insure the maintenance 

 of fish food and young fish supplies in these areas. 



The Fort Peck area was given a general survey and preparati(His 

 made for the continuation of this work this spring, when the con- 

 struction will have proc-eeded further. 



