Ash Creek, the Patuxent River, and Back Creek, 194-7 (Siirber and 

 Friddle 1949), mortality or fishes reached a peak v^itnin tvro days 

 after spraying. 



Eacn 01 the daphnia ponds were again stocked on October 1/+, 

 1946 with 300 fish I50 each of black crappies, bluegills, large- 

 mouth and smallmouth black bass, rainbow trout, and golden shiners. 



Ponds 1 and 2 were used as controls. Ponds 3 and 4 were 

 sprayed with DDT suspension formula 3> anu ponds 5 and 6 with susi:)en- 

 sion formula 2, both at the rate of one pound of DDT per acre (0.18 

 p.p.m.). All fish were fed a regular hatchery trout diet once each 

 day. The average water temperature from October 22 tlirough Novem- 

 ber 6 was 60.3° F. No running water was permitted to flow into the 

 ponds during this experiment. Despite the 'act that the water tem- 

 perature reached 69.0° F., no loss of trout occurred in tne control 

 ponds. 



Inasmuch as the condition of tlie fish has proved to be an im- 

 portant factor in their ability to withstand DDT, it is pointed out 

 that tne rainbow trout, golden shiners, largemouth black bass, and 

 bluegills were recently removed from ponds in which they were well 

 fed. The smallmouth black bass and black crappies, however, had 

 been in holding ponds at' least a week. 



Both suspensions seriously affected black crappie, smallmouth 

 black bass and bluegills Ct^ble 6). Nearly all of tnese species 

 were killed by the one-pound-per-acre treatments. The golden shiners, 

 rainbow trout, and largemouth black bass were relatively unaffected. 



Although the primary objective of the experiment Tras to compare 

 sensitivity of trout, a cold-water species, with that of warm-water 

 species of fish under similar conditions in which it was known the 

 fish would get full exposure to the poison, these data also furnish 

 evidence that the larger fingerling fish can withstand more DDT than 

 fry or fish about one inch long (see table 2 and pageH). The results 

 of the experiment also show that well-fed rainbow trout and golden 

 shiners can withstand a one-pound-per-acre treatment with DDT in sus- 

 pension. Ihe smallmouth black bass proved to be riore suscejjtible to 

 DDT than the largemouth black bass. This may have been due to the 

 condition of the fish because in a previous exiJeriment, largemouth 

 black bass appeared somewhat more sensitive than the smallmouth black 

 bass (table 5). The crappies died in large numbers immediately after 

 spraying. Heavy losses in smallmouth black bass and bluegills oc- 

 curred two to four days after treatment. 



On August 23, 1946 nine dirt-bottomed ponds were each stocked 

 with 350 fish — 50 each oi golden shiners (4.1 inches in length), and 



15 



