Suspension Formula (formula 2) yrettable powder) at 0.5 pound 

 per acre caused serious losses in all three ponds. Hiese losses 

 were less than in tlie ponds treated with an oil formula (formula 5)» 

 The brovm bullhead may oe less sensitive to DDT in suspension than 

 the bluegill. The results were variable, but considerable numbers 

 of fish survived as shown in table 3» 



Eight aquaria filled with 20 liteirs of water were stocked on 

 January 24, 194-7, with four bluegills, four rainbow trout and four 

 brook troixt each. These species were of the following sizes, re- 

 spectively: 1.1 inches, 1.0 inches, and 0.9 inches. The water tem- 

 perature averaged 61.8° F. On January 28, 1947, thjree aquaria were 

 sprayed with DDT suspension (formula 2) at the rate of 0.5 pound 

 per acre (0.28 p.p.m.), and trj:"ee aquaria were sprayed with DDT in 

 oil (formula 5) at 0.5 pound DDT per acre (0.28 p.p.m.). Two 

 similarly stocked aquaria remained untreated. All fish died in the 

 sprayed aquaria j the heaviest mortality occurring on the second and 

 third days after spraying. The experiment was concluded on February 



Experiments with Older Fishes 



Three examples of the ability of large f ingerling and adult 

 fish to withstand high concentrations of DDT were cited by Surber 

 (1946). Jn one instance, two small dirt-bottoraed ponds which T»ere 

 stocked with 50 sraallmouth bass (average length 3.7 inches), and 

 50 bluegills (average length about 3«8 inches), were sprayed on 

 September 8, 1945, with a DDT oil solution (formula 5) at the rate 

 of one pound of DDT per acre, O.I4 and 0,13 p.p.m., respectively. 

 Losses totaled 4t> and 5-4 percent, respectively, of the smallmouth 

 bassj 24 and 8 percent of the bluegills. 



In a second instance, a 0»35 acre dirt-bottomed pond containing 

 20 adult largemouth black bass, 10 to I5 inches, and 40 adult blue- 

 gills, 6 to 7 inches, -was sprayed with DDT in kerosene at the rate 

 of one pound per acre (0.I4 p.p.m.) on September 13> 1945, and again 

 on September 20, without loss of a fish. 



In the third experiment, October 24, 1945, three dirt-bottoned 

 ponda containing 50 bluegills 3,b inches in length, and 50 large- 

 mouth black bass averaging 4.9 inches, were sprayed with DDT and 

 xylene in fuel oil No. 2 (formula 5) at one pound of DDT per acre. 

 Fifty to 60 percent of the bluegills were killed, but the treatment 

 had little effect on the f ingerling bass. The maximum theoretical 

 concentrations of DDT in the series of experiments ranged from O.I4 

 to 0.17 p.p.m. The three ponds were restocked with the same species 

 of fish of comparable size. A suspension of DDT used at the above 

 rate aid not kill the bass. One-half the bluegills were found dead 

 in one of the three ponds, and one bluegill in another. 



11 



