and 0.56 kg. per hectare killed salmon, trout, 

 and suckers in streams in New Brunswick 

 (Ker swill and El son, 1955). In nny study, 

 rainbow trout held in cages at the stream 

 mouths were apparently unaffected by the 

 application of DDT at the rate of 0.28 kg. 

 per hectare, and no fish showed symptoms of 

 DDT poisoning (erratic and uncoordinated 

 swimming, tremors, and gulping of air at 

 the surface-- Rudd and Genelly, 1956) in Cabin 

 Creek or the Virginia Creek system after 

 the spraying. Trout from the stream and lake 

 in the treated watersheds showed no evidence 

 of blindness as reported by Alderdice and 

 Worthington (1959) who held coho salmon in 

 aquariums in DDT concentrations of 0.36 p. p.m. 

 The effects of the high concentrations of DDT 

 and DDE in tissues of cutthroat trout in 

 Virginia Lake were not assessed. The mean 

 condition factor of the fish from Virginia Lake 

 continued to decline in 1964, but this decrease 

 may have been a result of a decrease in the 

 aquatic insects in the lake rather than the 

 effects of DDT itself. No attempt was made 

 to determine the abundance of aquatic in- 

 sects in the lake. The lower condition factor 

 of fish in Cabin Creek after spraying in 

 1963 was probably due to the lack of aquatic 

 insects, which were scarce in the stream 

 and in trout stomachs. 



Clams and Plankton 



Trace amounts of DDT and DDE were found 

 in 14 of the 15 samples of clams. A prespray 

 sample from the vicinity of Cabin Creek con- 

 tained 0.03 p. p.m. DDE. The filter feeding and 

 long life of clams should give them a great 

 potential for accumulation of DDT and DDE. 

 Only trace amounts of DDT were found in 

 samples of plankton. Because we do not know 

 how long the plankton remained in the vicinity 

 of the creek, these data may not be meaning- 

 ful. Measurement of effects on marine clams 

 and plankton should be included, however, if 

 a widescale insecticide program is begun in 

 southeastern Alaska. 



CONCLUSIONS 



Although direct harmful effects on fishes 

 from DDT sprayed at the relatively low rate 

 of one-fourth pound per acre were not demon- 

 strated in this study, the accompanying drastic 

 reduction of aquatic insects could reduce 

 growth and survival significantly. The effect 

 of a reduction in aquatic insects would vary 

 among different species of fish. Pink and 

 chum salmon would be relatively unaffected 

 by a program for control of the black-headed 

 budworm with DDT because the optimum 

 time for achieving maximum kill of the in- 

 sect is in early summer. Pink and chum 



salmon fry migrate to sea in the spring, 

 and the adult spawners enter the streams in 

 midsummer and late summer. Furthermore, 

 these two species do not feed extensively in 

 fresh water. Sockeye salmon, coho salmon, 

 and king salmon (O. tshawytscha ) could be 

 affected seriously, however, because a sub- 

 stantial portion of their lives is usually spent 

 in streams and lakes where aquatic insects 

 maybe a significant part of their food (Synkova, 

 1951; Merrell, 1964). 



The present study has shown that condition 

 factors of trout resident in streams were 

 reduced for at least 2 yr. after the watershed 

 was sprayed with DDT. Control of forest 

 insects with aerial application of DDT in 

 watersheds containing lakes and streams thus 

 may have adverse effects on coho, sockeye, 

 and king salmon and on trout. 



ACKNOWLEDGMENTS 



Roger Blackett, James Dinsmore, Raymond 

 Evans, David Hall, Tom Huff, Jay Richardson, 

 and Douglas Ross, seasonal Fishery Aids, 

 assisted in the field work. Mr. and Mrs. 

 Michael Gallatin made available to the project 

 all of the facilities of their homestead near 

 the mouth of Old Tom Creek, and their as- 

 sistance was a major contribution to the 

 successful completion of the study. Theodore 

 R, Merrell, Jr., Chief of Pink and Chum 

 Salmon Investigations, Bureau of Commercial 

 Fisheries Biological Laboratory, Auke Bay, 

 gave advice during the field work and reviewed 

 the manuscript extensively. Loyal Bouchard 

 preceded me as project leader on the study, 

 and parts of the experimental design were 

 originally suggested by him. 



LITERATURE CITED 



ADAMS, LOWELL, MITCHELL G. HANAVAN, 

 NEIL W. HOSLEY, and DAVID W. JOHNSTON. 

 1949. The effects on fish, birds, and mam- 

 mals of DDT used in the control of 

 forest insects in Idaho and Wyoming. 

 J. Wildl. Manage. 13: 245-254. 

 ALDERDICE, D. F., and M. E. WORTHINGTON. 

 1959. Toxicity of a DDT forest spray to 

 young salmon. Can. Fish Cult. 24: 41- 

 48. 

 BRIDGES, W. R., and AUSTIN K. ANDREWS. 

 1961. Effects of DDT spray on fish and 

 aquatic insects in Gallatin River drain- 

 age in Montana. U.S. Fish Wildl. Serv., 

 Spec. Sci. Rep. Fish. 391, ii +4 p. 

 COPE, OLIVER B. 



1961. Effects of DDT spraying for spruce 

 budworm on fish in the Yellowstone 

 River system. Trans. Amer. Fish. Soc. 

 90: 239-251. 



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