minimum of 96 percent sodium cyanide. On 

 each day that tests were run a fresh solution 

 of sodium cyanide was prepared. A pellet was 

 crushed and 1 gram of it was weighed and dis- 

 solved in 200 milliliters of distilled water. The 

 addition of measured quantities of this solution 

 to the test aquariums containing the diluent pro- 

 vided the desired concentrations which were 

 recorded in p.p. m . sodium cyanide . 



Although the test solutions were not 

 aerated artificially for any of the laboratory 

 experiments and no determinations were made, 

 the dissolved oxygen concentrations were ap- 

 parently sufficient. Proper controls were run 

 for each of the tests, and no loss of fishes 

 occurred in control aquariums daring the course 

 of the experiments . 



Fish were removed from the holding 

 tanks and placed in an aquarium containing the 

 diluent 10 to 15 minutes before the addition of 

 the desired concentration of poison. If 100- 

 percent mortality did not occur within 72 hours 

 the tests were terminated. Continuous observa- 

 tions of the behavior of the fishes were made 

 for 2 or 3 hours and if complete mortality had 

 not occurred within this period, further observa- 

 tions were made at irregular intervals as 

 necessary. When there was no response to 

 gentle prodding, the fishes were considered to 

 be dead and the time required to produce 100- 

 percent mortality was recorded to the nearest 

 one-tenth of an hour. 



The green sunfish was the only species 

 used in laboratory tests designed to indicate the 

 duration of the toxicity period. Test solutions 

 used were chosen from those that had produced 

 100-percent mortality in toxicity experiments. 

 Beginning 24 hours after the addition of the poison 

 groups of test fish were placed in an aquarium 

 containing the test solution at intervals of 24 

 hours until all fish in each group survived for 

 24 hours. The surviving fish were then observed 

 for one week . The percentage of survival at 

 24, 48, 72, and 168 hours was noted for each 

 group . 



Green sunfish and largemouth bass were 

 used in laboratory experiments to determine if 

 the fishes would revive after being removed 

 from solutions of the poison. Four test fish were 



transferred from the holding tanks to an aquar- 

 ium containing the diluent. The fish were 

 allowed a period of 10 to 15 minutes to settle 

 down. Enough poison was added to make the 

 concentration 1 p. p.m. After being exposed 

 for a designated period, two fish were removed 

 and placed in an aquarium containing untreated 

 water similar to the diluent. The time required 

 for complete revival was noted. The fish were 

 considered to be completely revived if they ex- 

 hibited normal response to external stimuli. 

 After their revival, the fish were observed for 

 at least 1 week to determine their survival. 

 The time required to produce 100 -percent mor- 

 tality was noted for the two fish that remained 

 in the test solution. 



MATERIALS AND METHODS FOR 

 FIELD EXPERIMENTS 



Eight farm ponds or pools near Carbon - 

 dale, Illinois, were used for the field experi- 

 ments. Table 1 presents some of the physical 

 and chemical characteristics and the kinds of 

 fish in each pond. In addition, the concentration 

 of sodium cyanide used and its method of applica- 

 tion for each pond is shown. The poison was 

 applied in two ways. For the larger ponds, a 

 burlap sack containing the pellets of sodium 

 cyanide was suspended from a stake in the wash 

 of a 10 -horsepower outboard motor placed either 

 on a boat or a rack and, generally, allowed to 

 run at about half throttle for 10 minutes and then 

 shut off. For the smaller ponds, the pellets 

 were dropped into a small -meshed dip net and 

 allowed to dissolve while the net was being moved 

 through the water around the edees of the pond. 

 All pH values were determined colorimetrically, 

 except that in pond 7, which was determined 

 electrometrically . 



The effectiveness of the toxicity of the 

 poison was estimated for six ponds by using the 

 results from intensive seining operations. 

 These estimates were further supported by ob- 

 servations made during and following poisoning 

 operations . 



Determination was made of the duration 

 of toxicity in two ponds. Twenty -four hours 

 after the poison had been applied a group of 6 

 green sunfish in a wire cage was placed in the 

 pond at a depth of approximately 3 feet. 



