Their general reaction to the poison was sim- 

 ilar to that exhibited to deficient concentrations 

 of dissolved oxygen. The general pattern of 

 behavior, particularly that of the green sunfish 

 in solutions of 1 p. p.m. of sodium cyanide, is 

 described below: 



to 10 minutes. --The fish appeared normal, 



3 to 30 minutes. --The fish surfaced. This 



action was in some cases preceded or 

 followed by vigorous swimming. Dur- 

 ing the latter part of this period they 

 began to lose equilibrium and sink. 



20 to 50 minutes. --This was a period character- 

 ized by alternate surfacing and sinking 

 as the fish regained their equilibrium 

 only to lose it again. 



After 50 minutes. --The fish exhibited a final 

 loss of equilibrium and sank to the bot- 

 tom of the aquarium before death 

 occurred. 



Bass tended to surface at about the same 

 time as the green sunfish. However, the per- 

 iods outlined above were somewhat shorter. All 

 of the periods were longer in the cases of carp 

 and goldfish. The yellow bullhead showed a 

 definite tendency not to surface and remained 

 on the bottom of the aquarium until equilibrium 

 was lost for the first time. The longnose gar 

 surfaced almost immediately and remained at 

 the surface gasping air until equilibrium was 

 lost. Lower concentrations of poison tended to 

 lengthen the periods while higher concentrations 

 shortened them. At lower temperatures the 

 time required to produce complete mortality 

 was extended, but the length of period where 

 the fish surfaced differed little from those at 

 higher temperatures. All periods tended to be 

 longer at the higher pH values. 



During the later part of the surfacing 

 period and thereafter fishes generally could be 

 caught easily with the hand. 



In field experiments removal operations 

 were conducted on six ponds. General informa- 

 tion on these ponds appears in table 1 . A sum- 

 mary of these operations and the results are 

 presented below: 



Pond 2. --Attempts were made to remove 

 only the bass present. They were removed by 



two men along the edges of Che pond and one in 

 a boat using dip nets. Fishes started surfacing 

 approximately five minutes after the application 

 of poison was started. At this time removal 

 operations were begun and were stopped 40 min- 

 utes later. Thirty bass were removed and 

 placed in buckets of fresh water that had been 

 taken from the pond prior to poisoning. Twenty- 

 eight of these fish were transported to a clean 

 pond 11 miles distant. Upon arrival and sub- 

 sequent stocking, all fish seemed to be in 

 excellent condition. Survival was good; later 

 observations of the stocked pond revealed no 

 dead fish. Bass were observed feeding from 2 

 to 10 weeks following the operation. Two of the 

 bass were transported to the laboratory and ob- 

 served for one week . They suffered no apparent 

 ill effects. To indicate the effectiveness of re- 

 moval, the poisoned pond was observed for one 

 week. There were great numbers of dead golden 

 shiners and bullheads floating on the surface, 

 but only two dead bass were detected. 



Ponds 3 and 4. --Removal operations con- 

 ducted on ponds 3 and 4 were similar. Green 

 sunfish and golden shiners were removed from 

 pond 3 and green sunfish, golden shiners, and 

 black and yellow bullheads were removed from 

 pond 4. In both ponds, removal operations by 

 two men in waders using dip nets were begun 

 when the fishes started surfacing 15 minutes after 

 application of poison was started. Removal op- 

 erations were conducted for 45 minutes in pond 3 

 and 75 minutes in pond 4. Twenty-five shiners 

 and 31 green sunfish were removed from pond 3. 

 Thanumbers of fishes taken from pond 4 were: 

 bullheads, 201; golden shiners, 125; and green 

 sunfish, 29. The green sunfish and bullheads 

 were transported to the laboratory 20 miles away 

 and observed for two weeks. In this period ap- 

 proximately 25 percent of the green sunfish and 

 10 percent of the bullheads were lost. (Loss of 

 other fishes in the laboratory occurred at the 

 same time owing to a sudden increase of chlorine 

 in the water.) The golden shiners were trans- 

 ferred to other ponds within 100 yards of the 

 poisoned pond. Later observations and seining 

 operations indicated that survival was good. On 

 the basis of the number of dead fishes later 

 counted on the poisoned ponds approximately 95 

 percent of the sunfish and shiners and 70 percent 

 of the bullheads were removed. 



