BIOLOGICAL SURVEY OF THE UPPER MISSISSIPPI RIVER 



167 



14. It was suggested that dissolved oxygen is the controlling factor in the 

 distribution of fish in the polluted upper Mississippi River. The paucity in the 

 variety of bottom foods in the polluted areas may be a minor factor in the distribu- 

 tion of fish that subsist mainly on bottom fauna. Plankton, as food, is not a factor 

 in the distribution of the fish, for plankton was abundant, both in individuals and 

 in species, in polluted as well as in unpolluted waters. 



15. It was suggested further that the data indicate that the pollution of the 

 upper Mississippi River is severe only (in so far as fish are concerned) during the 

 periods of minimum discharge — that is, the periods of low water. It is highly 

 desirable that the distribution of the fish be studied through the various periods of 

 minimum and maximum discharge. 



BIBLIOGRAPHY 



Forbes, Stephen A., and R. E. Richardson. 



1913. Studies on the biology of the upper Illinois River. Bulletin, Illinois State Laboratory 

 of Natural History, Vol. IX, 1910-1913 (1914), Art. X, pp. 481-574, Pis. LXV- 

 LXXXV, tables. Urbana. 

 Richardson, Robert E. 



1925. Illinois River bottom fauna in 1923. Ibid., Vol. XV, 1924-1925 (1926), Art. VI, 

 pp. 391-422. Urbana. 

 Shelford, Victor E. 



1917. An experimental study of the effects of gas wastes upon fishes, with especial reference 

 to stream pollution. Ibid., Vol. XI, 1917, Art. VI, pp. 381-412, 4 tables, I PI. 

 Urbana. 



Standing Committee on River Pollution, Ministry of Agriculture and Fisheries, Great 

 Britain. 



1924. River pollution and fisheries. An introductory, nontechnical report on the work of 



the standing committee on river pollution, appointed in 1921. 42 pp. His Majesty's 

 Stationery Office, London. 

 Thompson, David H. 



1925. Some observations on the oxygen requirements of fishes in the Illinois River. Bulletin, 



Illinois State Natural History Survey, Vol. XV, 1924-1925 (1926), Art. VII, pp. 423- 

 437. Urbana. 

 Wundsch, H. H. 



1926. Die Reinhaltung unserer Fischgewasser. Handbuch der Biennenfischerei Mittel- 



europas, Vol. IV, Part 2. 



J* 



