Table 3. — Concentrations of DDT anci DDE in materials collected from four streams, Prince of Wales 



Island, Alaska, before spraying 



[Each figure represents one sample. N.D., not detectable] 



OBSERVATIONS ON THE DATES 

 OF SPRAYING 



Observations were made in the test and 

 control streams during the day of spraying 

 to measure the immediate results. Samples 

 of water (for DDT analysis) and drifting 

 insects were collected at 2-hr. intervals 

 starting 1 hr. after spraying began. In early 

 June, rainbow trout were collected in Old 

 Tom and Old Franks Creeks. Some of these 

 fish were preserved for DDT determination,^ 

 and others were placed in cages in each of 

 the four study streams. Some of the trout 

 from the cages and clams or plankton from 

 the vicinity of the two creeks were collected at 

 the end of the day of spraying for DDT analysis. 



Spraying of the insecticide began with the 

 Virginia Creek watershed on June 18, 1963, 

 but was discontinued after about one-third 

 of the area had been treated. Strong winds 

 arose suddenly and carried some spray out 

 of the target area. 



The first observations on the day of spray- 

 ing were of the immediate results of the in- 

 complete spraying of the Virginia Creek area. 

 Collections were made in both Virginia Creek 

 and its control stream, Saltery Cove Creek. 

 Because the odor of the spray mixture was 

 detected downwind from the Virginia Creek 

 watershed at Cabin and Old Franks Creeks, 

 the waters of these two streams were also 

 sampled. 



Apparently, little or no spray reached these 

 streams on June 18. Neither the nunnber of 

 drifting insects (tables 4 and 5) nor the DDT 

 in the water (table 6) increased. Only normal 

 levels (trace) of DDT were found in the fish 

 held in cages in Virginia and Saltery Cove 



and 



clams taken near the 



The fish tested contained only trace amounts of DDT 

 and DDE. 



Creeks 

 creeks. 



The rest of the Virginia Creek watershed 

 and all of the Cabin Creek watershed were 

 sprayed on June Zl under ideal conditions. 



After the spraying on June 21, the first 

 catches of drifting insects (1 hr. after spray- 

 ing) indicated that DDT had entered the test 

 streams; drifting Diptera and Ephemeroptera 

 (nnostly dead or dying) were many times more 

 abundant in the test than in the control streams. 

 The greatest nun-ibers of insects were caught 

 3 hr. after spraying; later samples contained 

 progressively fewer. Only a few drifting in- 

 sects (all alive and apparently normal) were 

 captured in the control streams (Old Tom 

 and Saltery Cove Creeks). A similar marked 

 increase in the nunnber of drifting insects in 

 streams soon after spraying has been recorded 

 by other investigators: Bridges and Andrews 

 (1961) and Cope (1961) in Montana; Frey 

 (1961) in Georgia; and Hoffman and Surber 

 (1948) in West Virginia. In these earlier ex- 

 periments, however, DDT was applied at a 

 rate of 1.12 kg. per hectare, in contrast to 

 0.28 kg. per hectare in southeastern Alaska. 



No evidence appeared of distress or nnor- 

 tality of the fish in the cages at the mouth of 

 each of the four streams or free in the 

 streams. 



The presence of significant quantities of 

 DDT in the sprayed streams that was in- 

 dicated by the increased number of drifting 

 insects was verified by the analysis of the 

 water collected on June 21 (table 6). The 

 DDT- contaminated water was flushed out of 

 Cabin Creek within 10 hr., but a concentration 

 of 0.5 p.p.m. was still present in Virginia 

 Creek after 12 hr. Water samples from the 

 inlet to Cabin Lake shortly after spraying 

 showed only trace amounts of DDT; little 

 spray reached the stream above the lake. 



