Jackson and Starrett (1959) found that an increase in wind velocity 

 from light to strong increased turbidity from 162 to 700 Jackson 

 turbidity units (JTU) and that a calm period of 7 to 12 days was 

 necessary for much of this sediment to settle from Lake Chautauqua. 

 As a consequence, this lake and other bottomland lakes remain highly 

 turbid most of the time. 



The turbidity levels in bottomland lakes and backwaters along 

 the Illinois River are within the range that reduces fish production. 

 Buck (1956) studied fish production in farm ponds, hatchery ponds, and 

 reservoirs in Oklahoma which had a wide range of turbidities. The farm 

 ponds were rotenoned, then restocked with largemouth bass and bluegills 

 or largemouth bass and redear sunfish. A total of 12 farm ponds was 

 divided into 3 turbidity classes. After two growing seasons, the aver- 

 age total weights of fish were: 



clear ponds (less than 25 JTU) 161.5 lb/acre 



intermediate ponds (25-100 JTU) 94.0 lb/acre 



muddy ponds (100 JTU) 29.3 lb/acre 



The redear and bluegill sunfish reproduced more abundantly and grew 

 faster in clear water. Survival of bass was greater in intermediate 

 ponds than in clear ponds, perhaps due to competition with abundant 

 sunfish populations in the clear ponds. However, the surviving bass 

 grew faster in clear ponds: 



average 



length 



increase 



6.9 in. 



5.1 in. 



2.4 in. 



The results from hatchery ponds, where turbidities were arti- 

 ficially controlled, and from the reservoirs, generally paralleled the 

 results from the farm ponds. 



Ellis (1936) found that organic matter mixed with erosion silt 

 created an oxygen demand in water and that the oxygen demand was 



52 



