Table 7. —Concentrations of DDT and DDE in materials collected from test and control streams 

 beginning after first postspray rainfall on June 23, 1963, Prince of Wales Island, Alaska 



[Trace, < 0.005 p.p.m. in water, <0.02 p.p.m. in fish and clams] 



■"■ Fish from Old Franks Creek (unsprayed) contained 0.75 p.p.m. DDT on July 23 and 0.55 p.p.m. 

 on August 24, and 0.30 p.p.m. DDE on both dates. No other sanples were taken on these dates. 

 2 Fish collected from Virginia Lake. 



no aquatic insects could be found. In the con- 

 trol streams, the numbers of aquatic insects 

 had not changed fronn the normal prespray 

 summer abundance (figs. 2 and 4). Kerswill 

 and Elson (1955) reported little or no reduc- 

 tion in numbers of water mites after DDT had 

 been sprayed at 0.56 kg. per hectare, but 

 the only living insect larvae they found were 

 in a pool in a small tributary. 



Reductions in nunnbers of aquatic insects 

 have been observed in other studies of the 

 effects of DDT application on the watershed, 

 but complete eradication has never been re- 

 ported. Among investigators who reported 

 drastic reductions of aquatic insects after 

 DDT had been sprayed at the rate of 0.22 to 

 1.12 kg. per hectare were: Warner and 

 Fenderson;^ Crouter and Vernon (1959); 

 Graham and Scott;'' Ide (1957); Webb and 

 Macdonald (1958); Hoffman and Surber (1949); 

 Hoffman and Drooz (1953); and Kerswill and 



Warner, Kendall, and Owen C. Henderson. 1959. Ef- 

 fects of forest Insect spraying on northern Maine trout 

 streams. Maine Dep. Inland Fish. Game. Dtngell Johnson 

 Proj. F-8-R-7, 32 p. 



' Graham, Richard J., and David O. Scott. 1958. Effects 

 of forest insect spraying on trout and aquatic insects in 

 some Montana streams. U.S. Fish and Wlldl. Serv.,Mont. 

 State Fish Game Dep., and U.S. Forest Serv., Final Rep. 

 1956 and 1957, 50 p. 



Elson (1955). Todd and Jackson (1961) found 

 no significant mortality of aquatic insects or of 

 salmonids after a watershed had been sprayed 

 with DDT at the rate of 0.28 kg. per hectare, 

 but in their studies a strip 0.8 km. (0.5 mile) 

 wide was left unsprayed on each side of the 

 stream. 



Stomachs of rainbow and cutthroat trout 

 were collected periodically from July 1962 

 through August 1964. The contents of stomachs 

 of trout from one of the test streams. Cabin 

 Creek, in 1963 (after spraying) were markedly 

 different from those in 1962 and 1964 (fig. 6), 

 The number of empty stomachs and the per- 

 centage of terrestrial insects and debris 

 were much greater in 1963 than in 1962 or 

 1964. The feeding habits of cutthroat trout 

 fronn Virginia Lake in the other test water- 

 shed (fig. 7) and rainbow trout from the con- 

 trol streams, Old Tom Creek (fig. 6) and 

 Saltery Cove Creek (fig. 7), did not change 

 from 1962 to 1964. 



Changes in the diet of fish in a streann due 

 to changes in the abundance of aquatic insects 

 resulting from DDT applications have not 

 been well documented because of lack of 

 adequate prespray samples and control areas. 

 Food studies in conjunction with spraying of 

 DDT are discussed in several papers, among 

 which are Cope and Park (see footnote 7); 

 Graham and Scott (see footnote 9); and 



11 



