142 U.S. BUREAU OF FISHERIES 



In actual work the two sets of operations have been intimately 

 associated, each serving to further the interest of the other, so that 

 the distinction is less real than the headings would indicate. 



POLLUTION STUDIES IN THE MISSISSIPPI 



In cooperation with the Corps of Engineers, United States War 

 Department, the studies of the Mississippi River and its tributaries 

 with particular reference with fisheries problems as influenced by both 

 pollution and navigation have been continued during 1932. Three 

 portions of the Mississippi River were given particular attention. 



A survey of the Hastings Pool, that portion of the Mississippi 

 River impounded by the Hastings Dam and lying roughly between 

 Hastings and Minneapolis, Minn., was made with special attention 

 to the effects of the polluted waters held in this pool, on the lateral 

 and connecting sloughs and lakes. Detailed plankton and chemical 

 studies were made and a condensed report on this investigation is 

 now in the hands of the War Department and United States district 

 attorney for the Minneapolis district. These data will also be 

 included in the forthcoming report on the Mississippi River. 



Using the Engineer boat yards at Keokuk, Iowa, as headquarters, 

 observations on Lake Keokuk were continued at various times through 

 the spring, fall, and winter of 1932 in addition to the intensive studies 

 of this lake during the months of May, June, and July. The effects 

 of pollution, silt, and sudden changes in water level incident to the 

 run-off from storms, on water conditions, fish food, and the bottom 

 fauna were the major contacts. From these studies together with 

 those of the two previous summers a very complete picture of the 

 chemical, physical, and biological conditions now obtaining in this 

 artifical river lake is now available not only for the Misssssippi prob- 

 lems but as a standard for the evaluation of fisheries conditions in 

 other such river lakes. The action of silt on the basic fish food, 

 plankton, has been given special consideration throughout these 

 studies and correlations with the chemical and physical changes in 

 the water have been made. These findings as part of the Mississippi 

 River report are now being put in final form and soon will be avail- 

 able for publication. 



The United States Fisheries laboratory, quarterboat No. 348, and 

 appended boats, after serving as a base of operations for the studies 

 at Lake Keokuk were moved down river to Grafton, 111., early in 

 August, and a survey of the Mississippi River between Grafton, 111., 

 and Hannibal, Mo., was completed. This portion of the river had 

 been given little attention in the previous pollution work carried for- 

 ward by the unit. The Grafton-Hannibal survey occupied some 5 

 weeks during August and the first of September. 



Summarizing all of the Mississippi River studies which are being 

 united into a report covering the Mississippi River from Minneapolis 

 to Cairo, the Ohio from Cairo to Evansville, Ind., and the Tennessee 

 from Paducah, Ky., to the Hiwassee River above Chattanooga, the 

 enormous damage to fisheries and fishery industries by uncontrolled 

 erosion is outstanding. Operating with the silt are municipal sewage 

 and industrial wastes both greatly increasing the pollution hazards. 

 Data obtained throughout this survey show that the uncontrolled 

 introduction of silt into these streams has tremendously increased the 



