-27" 



and 2) the use of morphologically similar hatchery ponds would minimize 

 these natural variables and would facilitate a more complete return of the 

 fish populations through draining. The desired turbidities were then to be 

 created by artificial means, simulating as nearly as possible the range of 

 turbidities found in the farm ponds. It was hoped that by starting with 

 morphologically similar ponds the final results could be attributed more 

 definitely to the effects of the induced turbidities >, 



This work was done at the State Fish Hatchery at Durant, Oklahoma. The 

 ponds used were rectangular in shape, with average dimensions of 61 by 69.5 

 feet, holding an average of approximately 0.1 (range; 0.084 to 0111) acre 

 of water. Maximum depths were occasionally as low as 2=5 feet, due to evapor- 

 ation, but the ponds were periodically raised to depths of 3.5 feet. The 

 average depths were maintained at approximately 1.5 feet« The water supply 

 for the hatchery is pumped from the Blue River. The water is ordinarily 

 clear (less than 25 ppm), having the chemical characteristics shown in Table 6. 



METHODS AND PROCEDURES 



It was hoped initially" that some natural soil material could be found 

 that would remain in suspension in the pond waters and that the turbidities 

 could be controlled by the amount of such material added^ However, all 

 materials used rapidly settled out, apparently due to a high availability 

 of positive ions in the water causing the neutralization and flocculation 

 of the negatively charged clay colloids in the manner described by Irwin and 

 Stevenson (1951). An attempt was then made to find some agent that could pre- 

 vent or retard coagulation of the soil materials. After considerable exper- 

 imentation in the laboratory, the use of sodium silicate was found to be 



