Results of the Direct Feeding of lifettable DDT in Gelatin Capsules 



Eight smallmouth black bass, ranging in weight from 5 .5 to 8 

 grams each, were placed in individual aquaria. These fish were taught 

 to consume a trout diet contained in gelatin capsules. After 2 weeks 

 of tne training they were fasted for 3 days to make them hungry enough 

 to eat the capsules. Two of the fish (controls) were given capsules 

 with meat only. V/ettable DDT powder in gelatin capsules was given 

 two of the fish at the rate of 50 milligrams per kilogram of body 

 weight, two were given 100 milligrams per kilogram, and two were given 

 200 milligrams per kilogram. 



Before feeding, a small sunount of the meat diet was placed in- 

 side each capsule with the powder without mixing, so as to add weight 

 and cause the capsules to sink into the water. The capsules were also 

 coated with the meat before introduction into the aquaria. The fish 

 were fed the capsules containing DDT between 8:25 and 8:30 a.m., 

 November 15, 19^6. They showed symptoms characteristic of DDT poison- 

 ing by afternoon of the first day. By 9:00 a.m., the following day, 

 five of the six fish fed DDT were dead. Two leaped from the aquaria 

 during the night, probably as a result of their violent reactions to 

 DDT. The only live fish (one of the two receiving 50 milligrams per 

 kilogram) remaining, other than the controls, was lying on its side 

 and exhibiting convulsions on the morning of November 16. Death oc- 

 curred at 1 p.m. 



This experiment indicated tnat DDT given intragastrically, even 

 without solvents, was more toxic to smallmouth black bass than to 

 goldfish (Ellis, Westfall, and Ellis, 1944). 



Effect of Condition on the Ability of Rainbow Trout to Withstand DDT 



Six daphnia ponds (450 cubic feet of ?iater each) were stocked with 

 fifty 3 •7-inch rainbovf trout each on November 15, 194b. These were 

 well-fed hatchery trout. In three of the ponds the trout were fed a 

 regular hatchery diet, and in the remaining three ponds the fish were 

 fasted. On November 26, four ponds (two containing fed and two with 

 unfed trout) were sprajred with wettable DDT (formula 1) at the rate 

 of one pound of DDT per acre. Two other ponds (l with fed and 1 with un- 

 fed trout) seinred as controls. The average water temperature during 

 the period November 26 to Decemoer 8 was 43° F. 



'Hiere was no mortality in the control ponds . In the ponds which 

 were sprayed and the trout fed, the mortalities were 4 and 10 percent. 

 The sprayed ponas in which tne fish were not fed sulTered losses of 

 70 and 60 percent, respectively. This experiment indicates that fish 

 weakened by the lack of food are more susceptible to DDT poisoning 

 than well-fed fish. 



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