Ifeirch 18. The water temperature during the experimental period 

 averaged 54»2° F. No fresh vvater was added to the aquaria after 

 the initial filling. These DDT applications killed all but three 

 fish in the sprayed aquaria, and one out of 9 fish died in the 

 control • 



Nine dirt-bottcmed ponds were stocked with 200 each of the ad- 

 vanced fry of the sraallmouth black bass ( Micro pterus dolomieu ) and 

 the largemouth black bass (tfi.cropteru8 salmoides ) on June 4., 194-6. 

 The average size of the smallmouth black bass was 0.93 inches arxi 

 that of the largemouth black bass 0.97 inches. Three ponds were 

 left untreated as controls yrtiile the remaining six were sprayed with 

 two DDT formulations on June 6 (table 2). There was ample natural 

 iood for the fish as there had been no previous treatments in this 

 series of ponds during the 1946 season, and they were not drained 

 during the winter. The ponds were drained and inventoried June 18 

 and 19, 12 days after treatment. 



Eighty-eight percent of the bass were recovered from the con- 

 trol ponds, but no fish survived in the other ponds, with one ex- 

 ception. In the pond treated with an oil spray about 12 percent of 

 each species survived. In oil-sprayed ponds, the oil film is some- 

 times blown ashore by breezes. Removal of the film by a breeze or 

 a lower concentration of DDT may have accounted for the fact that 

 there was some survival in one pond. 



Oil Formulations 



Three daphnia ponds were stocked with 100 advanced fry of the 

 largemouth black bass which averaged 1.1 inches in fork length on 

 June 18, 1947. The fry were supplied an abundance of Daphnia magna 

 for food one day before ponds 1 and 2 were sprayed with oil formula 

 6 at the rate of 0.5 pound DDT per acre (0.09 p.p.m.) on June 19. 

 Pond 3 remained untreated. The average temperature during the ex- 

 periment was 72.0° F. iibout 85 percent of the fish present in the 

 two treated ponds were dead by the end of the second day, and no 

 live fish were recovered upon draining the ponds June 24. All fish 

 were recovered in the control pond. In the treated ponds, Daphnia 

 magna disappeared four days after treatment, although they were 

 abundant in the control pond at the conclusion of the experiment. 



lliese ponds were restocked with the same numbers of slightly 

 larger fish (average length, 1.25 inches) on June 29, 1947. A 0.25 

 pound per acre treatment (0.04 p.p.m.) on June 30 with oil spray 

 (formula 6) killed all the fish in the tiro experimental ponds, while 

 97 pei-cent of the fish survived in the control pond until July 7, 

 when the experiment was terminated. The heaviest mortality occurred 

 on the second day after treatment. The average temperature during 

 this experiment was 75*0° F. 



